| 1. |
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| 2. |
- Metzler, Veronika M., et al.
(författare)
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Androgen dependent mechanisms of pro-angiogenic networks in placental and tumor development
- 2017
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Ingår i: Placenta. - : W B SAUNDERS CO LTD. - 0143-4004 .- 1532-3102. ; 56, s. 79-85
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Tidskriftsartikel (refereegranskat)abstract
- The placenta and tumors share important characteristics, including a requirement to establish effective angiogenesis. In the case of the placenta, optimal angiogenesis is required to sustain the blood flow required to maintain a successful pregnancy, whereas in tumors establishing new blood supplies is considered a key step in supporting metastases. Therefore the development of novel angiogenesis inhibitors has been an area of active research in oncology. A subset of the molecular processes regulating angiogenesis are well understood in the context of both early placentation and tumorigenesis. In this review we focus on the well-established role of androgen regulation of angiogenesis in cancer and relate these mechanisms to placental angiogenesis. The physiological actions of androgens are mediated by the androgen receptor (AR), a ligand dependent transcription factor. Androgens and the AR are essential for normal male embryonic development, puberty and lifelong health. Defects in androgen signalling are associated with a diverse range of clinical disorders in men and women including disorders of sex development (DSD), polycystic ovary syndrome in women and many cancers. We summarize the diverse molecular mechanisms of androgen regulation of angiogenesis and infer the potential significance of these pathways to normal and pathogenic placental function. Finally, we offer potential research applications of androgen-targeting molecules developed to treat cancer as investigative tools to help further delineate the role of androgen signalling in placental function and maternal and offspring health in animal models.
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| 3. |
- Metzler, Veronika M., et al.
(författare)
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The KDM5B and KDM1A lysine demethylases cooperate in regulating androgen receptor expression and signalling in prostate cancer
- 2023
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Ingår i: Frontiers in Cell and Developmental Biology. - : Frontiers Media S.A.. - 2296-634X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Histone H3 lysine 4 (H3K4) methylation is key epigenetic mark associated with active transcription and is a substrate for the KDM1A/LSD1 and KDM5B/JARID1B lysine demethylases. Increased expression of KDM1A and KDM5B is implicated in many cancer types, including prostate cancer (PCa). Both KDM1A and KDM5B interact with AR and promote androgen regulated gene expression. For this reason, there is great interested in the development of new therapies targeting KDM1A and KDM5B, particularly in the context of castrate resistant PCa (CRPC), where conventional androgen deprivation therapies and androgen receptor signalling inhibitors are no longer effective. As there is no curative therapy for CRPC, new approaches are urgently required to suppress androgen signalling that prevent, delay or reverse progression to the castrate resistant state. While the contribution of KDM1A to PCa is well established, the exact contribution of KDM5B to PCa is less well understood. However, there is evidence that KDM5B is implicated in numerous pro-oncogenic mechanisms in many different types of cancer, including the hypoxic response, immune evasion and PI3/AKT signalling. Here we elucidate the individual and cooperative functions of KDM1A and KDM5B in PCa. We show that KDM5B mRNA and protein expression is elevated in localised and advanced PCa. We show that the KDM5 inhibitor, CPI-455, impairs androgen regulated transcription and alternative splicing. Consistent with the established role of KDM1A and KDM5B as AR coregulators, we found that individual pharmacologic inhibition of KDM1A and KDM5 by namoline and CPI-455 respectively, impairs androgen regulated transcription. Notably, combined inhibition of KDM1A and KDM5 downregulates AR expression in CRPC cells. Furthermore, combined KDM1A and KDM5 inhibition impairs PCa cell proliferation and invasion more than individual inhibition of KDM1A and KDM5B. Collectively our study has identified individual and cooperative mechanisms involving KDM1A and KDM5 in androgen signalling in PCa. Our findings support the further development of KDM1A and KDM5B inhibitors to treat advanced PCa. Further work is now required to confirm the therapeutic feasibility of combined inhibition of KDM1A and KDM5B as a novel therapeutic strategy for targeting AR positive CRPC.
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| 4. |
- Arvidsson, Martin, et al.
(författare)
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Multidimensional psychophysics : Surface feel of printing paper as a function of physical properties
- 2009
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Ingår i: Fechner Day 2009. - Galway, Irland : International Society for Psychophysics. ; , s. 215-220
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this experiment was to explore the perception of tactile surface-feel of 21 printing papers. A multidimensional scaling (MDS) experiment was conducted with 20 women. They scaled similarity among all possible pairs of the papers. Similarity measurements were mapped by INDSCAL and modeled with PREFMAP. Test-retest and concordance coefficients were high. It is not yet established what physical properties best determine tactile feel. It seems likely though that finger friction and surface roughness are strong contenders. Finger friction for the papers was measured as a ratio of friction force to normal force;(while stroking a human finger on the surface. Average surface roughness was measured with a profilometer. Physical properties were rotated into the 3D INDSCAL solution. This solution identified and mapped the tactile surface feel of the papers in an interpretable way with regard to i.e. friction, surface roughness and weight.
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| 5. |
- Atiomo, William, et al.
(författare)
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Expression of NAD(P)H quinone dehydrogenase 1 (NQO1) is increased in the endometrium of women with endometrial cancer and women with polycystic ovary syndrome
- 2017
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Ingår i: Clinical Endocrinology. - : John Wiley & Sons. - 0300-0664 .- 1365-2265. ; 87:5, s. 557-565
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Women with a prior history of polycystic ovary syndrome (PCOS) have an increased risk of endometrial cancer (EC). Aim: To investigate whether the endometrium of women with PCOS possesses gene expression changes similar to those found in EC. Design and Methods: Patients with EC, PCOS and control women unaffected by either PCOS or EC were recruited into a cross-sectional study at the Nottingham University Hospital, UK. For RNA sequencing, representative individual endometrial biopsies were obtained from women with EC, PCOS and a woman unaffected by PCOS or EC. Expression of a subset of differentially expressed genes identified by RNA sequencing, including NAD(P)H quinone dehydrogenase 1 (NQO1), was validated by quantitative reverse transcriptase PCR validation (n = 76) and in the cancer genome atlas UCEC (uterine corpus endometrioid carcinoma) RNA sequencing data set (n = 381). The expression of NQO1 was validated by immunohistochemistry in EC samples from a separate cohort (n = 91) comprised of consecutive patients who underwent hysterectomy at St Mary's Hospital, Manchester, between 2011 and 2013. A further 6 postmenopausal women with histologically normal endometrium who underwent hysterectomy for genital prolapse were also included. Informed consent and local ethics approval were obtained for the study. Results: We show for the first that NQO1 expression is significantly increased in the endometrium of women with PCOS and EC. Immunohistochemistry confirms significantly increased NQO1 protein expression in EC relative to nonmalignant endometrial tissue (P < .0001). Conclusions: The results obtained here support a previously unrecognized molecular link between PCOS and EC involving NQO1.
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| 6. |
- Harris, Anna E., et al.
(författare)
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Exploring anti-androgen therapies in hormone dependent prostate cancer and new therapeutic routes for castration resistant prostate cancer
- 2022
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Ingår i: Frontiers in Endocrinology. - : Frontiers Media S.A.. - 1664-2392. ; 13
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Forskningsöversikt (refereegranskat)abstract
- Androgen deprivation therapies (ADTs) are important treatments which inhibit androgen-induced prostate cancer (PCa) progression by either preventing androgen biosynthesis (e.g. abiraterone) or by antagonizing androgen receptor (AR) function (e.g. bicalutamide, enzalutamide, darolutamide). A major limitation of current ADTs is they often remain effective for limited durations after which patients commonly progress to a lethal and incurable form of PCa, called castration-resistant prostate cancer (CRPC) where the AR continues to orchestrate pro-oncogenic signalling. Indeed, the increasing numbers of ADT-related treatment-emergent neuroendocrine-like prostate cancers (NePC), which lack AR and are thus insensitive to ADT, represents a major therapeutic challenge. There is therefore an urgent need to better understand the mechanisms of AR action in hormone dependent disease and the progression to CRPC, to enable the development of new approaches to prevent, reverse or delay ADT-resistance. Interestingly the AR regulates distinct transcriptional networks in hormone dependent and CRPC, and this appears to be related to the aberrant function of key AR-epigenetic coregulator enzymes including the lysine demethylase 1 (LSD1/KDM1A). In this review we summarize the current best status of anti-androgen clinical trials, the potential for novel combination therapies and we explore recent advances in the development of novel epigenetic targeted therapies that may be relevant to prevent or reverse disease progression in patients with advanced CRPC.
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| 7. |
- Plunkett, M. A., et al.
(författare)
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Adsorption of a cationic polyelectrolyte followed by surfactant-induced swelling, studied with a quartz crystal microbalance
- 2002
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:4, s. 1274-1280
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and subsequent surfactant-induced swelling of a 10% charged cationic polyelectrolyte (AM-MAPTAC-10), on a gold surface, was monitored by means of a quartz crystal microbalance with dissipation (QCM-D). This instrument gives information on the total adsorbed amount including any adsorbed solvent and on the manner of adsorption. In this case the total adsorbed amount from a 20 ppm AM-MAPTAC-10 solution registered by the QCM-D device was approximately 0.6 mug cm(-2). X-ray photoelectron spectroscopy results showed that the polyelectrolyte adsorbed mass was 0.16 mug cm(-2); thus the water trapped within the polyelectrolyte layer constitutes about 70% of the mass measured by the quartz crystal microbalance. The adsorption process was found to be rather complex, though the time evolution of the adsorbed mass indicated that the majority of the process was diffusion controlled, Toward the end of the adsorption process, the rate of adsorption drops off and the dissipation rate increases, indicating that as the surface becomes crowded the layer extends further in the direction normal to the surface. The effect of addition of sodium dodecyl sulfate (SIDS) to a preadsorped AM-MAPTAC-10 layer was also investigated. It was found that some swelling of the preadsorbed layer occurred once the bulk surfactant concentration reached 20% of the critical micelle concentration (cmc). Between 60% of the cmc and twice the cmc, the adsorbed layer swelled significantly and desorption started to occur. Rinsing the surface with the surfactant-free electrolyte solution results in a rapid decrease in dissipation and adsorbed mass indicating the removal of the surfactant but not the polyelectrolyte.
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| 8. |
- Plunkett, M. A., et al.
(författare)
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Comparison of the adsorption of different charge density polyelectrolytes : A quartz crystal microbalance and X-ray photoelectron spectroscopy study
- 2003
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:11, s. 4673-4681
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of a series of six cationic polyelectrolytes onto a gold surface was monitored via a quartz crystal microbalance with dissipation (QCM-D). The series of polyelectrolytes were chemically similar but differing in the ratio of two randomly ordered constituent monomers, one of which was charged, the other neutral. Thus the series of polyelectrolytes differed systematically in their charge densities, ranging from a high charge density (100% of monomers charged) to a low charge density (1% charged). It was determined that high charge density polyelectrolytes adsorbed in a relatively flat and rigid layer, while the low charge density polyelectrolyte, as expected, adsorbed in a much more extended structure that coupled strongly to the bulk solvent. By comparison to X-ray photoelectron spectroscopy results, we have also calculated the relative solvent mass hydrodynamically coupled to the adsorbed polymer, which ranges from almost 80% solvent for the 1% charged case down to close to zero for the 100% charged case. Since the QCM-D results are measured relative to uncoated gold in aqueous solution, the latter results should be interpreted as showing that the amount of water hydrodynamically coupled to gold and that coupled to gold coated with the 100% charged polyelectrolyte is very similar. It is believed that this systematic study on the effect of polyelectrolyte structure on the measured dissipation change in the QCM-D may serve as a first guide when inferring structural and viscoelastic information based solely on the QCM-D technique for other similar systems. In addition, a preliminary study on the ability of one polymer to replace another preadsorbed polymer layer was conducted that showed that a steric layer was able to prevent the adsorption of a thermodynamically more favorable polymer. In the reverse case, greater exchange was possible.
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| 9. |
- Rundlöf, M., et al.
(författare)
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Application of the JKR method to the measurement of adhesion to Langmuir-Blodgett cellulose surfaces
- 2000
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 230:2, s. 441-447
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Tidskriftsartikel (refereegranskat)abstract
- The JKR method has been applied for studying adhesion between poly(dimethylsiloxane) (PDMS) caps and Langmuir-Blodgett cellulose surfaces including the substrate, hydrophobized mica, and two flat mineral surfaces, bare mica and glass, The self-adhesion of PDMS caps and oxidized PDMS caps are included as a reference to compare with literature data. The results of the measurements have been compared with previous studies using the surface force apparatus and similar systems. A satisfactory agreement is obtained for simple systems showing no, or very limited, hysteresis between loading and unloading curves, In several cases, however, a large hysteresis is found between loading and unloading curves, with a larger adhesion measured from the pull-off force than from the JKR-curve determined on loading. This is, for instance, the case for PDMS against cellulose. The situation is analogous to that found in wetting studies showing a large hysteresis between advancing and receding contact angles.
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| 10. |
- Skedung, Lisa, et al.
(författare)
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Tribology, texture and touch
- 2014
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Ingår i: 5th World Tribology Congress, WTC 2013. - 9781634393522 ; , s. 2270-2273
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Konferensbidrag (refereegranskat)
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| 11. |
- Tyrode, E, et al.
(författare)
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A vibrational sum frequency spectroscopy study of the liquid-gas interface of acetic acid-water mixtures: 2. Orientation analysis
- 2005
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Ingår i: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207. ; 109, s. 329-341
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational sum frequency spectroscopy has been used to investigate the surface of aqueous acetic acid solutions. By studying the methyl and carbonyl vibrations with different polarization combinations, an orientation analysis of the acetic acid molecules has been performed in the concentration range 0-100%. The surface tension of acetic acid solutions was also measured in order to obtain the surface concentration. The orientation of the interfacial acetic acid molecules was found to remain essentially constant in an upright position with the methyl group directed toward the gas phase in the whole concentration range. The tilt angle (CH3) of the symmetry axis of the methyl group with respect to the surface normal was found to be lower than 15 when considering a distribution of angles or as narrow as 0 ± 11 when assuming a Gaussian distribution. Further investigations showed that the C=O bond tilt (C=O) of the acetic acid hydrated monomer was constant and close to 55 in the concentration range where it was detected. Finally, the orientation information is discussed in terms of different species of acetic acid, where the formation of a surface layer of acetic acid cyclic dimers is proposed at high acid concentrations.
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| 12. |
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| 13. |
- Abraham, T., et al.
(författare)
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Polyelectrolyte-mediated interaction between similarly charged surfaces : Role of divalent counter ions in tuning surface forces
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:26, s. 8321-8327
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Tidskriftsartikel (refereegranskat)abstract
- The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw similar to 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale R-G of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Angstrom due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH similar to8.0-9.0, in contrast to the case of 3 MM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Angstrom followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH similar to8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.
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| 14. |
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| 15. |
- Arnebrant, Thomas, et al.
(författare)
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Lubricating Properties of the Initial Salivary Pellicle
- 2003
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Ingår i: Biofouling (Print). - : Harwood Academic Publishers. - 0892-7014 .- 1029-2454. ; 19:6, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- The role of saliva in the oral cavity is manifold; an important function is to serve as lubricant between hard (enamel) and soft (mucosal) tissues. Intraoral lubrication is of crucial importance in order to maintain functions such as deglutition, mastication and the faculty of speech. A large number of people suffer from impaired salivary functions, displaying symptoms such as 'dry mouth'. This results in a need for methods to assess the lubricating properties of both native saliva and potential artificial saliva formulations. Here, normal as well as lateral forces, acting between adsorbed salivary films, have been measured for the first time by means of colloidal probe atomic force microscopy (AFM). It was found that the presence of salivary pellicles between hard surfaces reduces the friction coefficient by a factor of 20. This reduction of friction is consistent with the long-range purely repulsive nature of the normal forces acting between the salivary films. The lubricating mechanism is presumably based on a full separation of the sliding surfaces by the salivary films. The friction between salivary films has been investigated at normal loads that cover the clinical jaw closing forces, and it can be concluded that the lubricating properties are maintained within this load interval. The present study indicates the usefulness of colloidal probe AFM, which offers a direct and quantitative measure of lubrication at a molecular level, in the study of biotribological phenomena. In particular, the results obtained here may have implications for the development of saliva substitutes.
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| 16. |
- Arvidsson, M., et al.
(författare)
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Feeling fine - the effect of topography and friction on perceived roughness and slipperiness
- 2017
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Ingår i: Biotribology. - : Elsevier Ltd. - 2352-5738. ; 11, s. 92-101
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Tidskriftsartikel (refereegranskat)abstract
- (1) Background. To design materials with specific haptic qualities, it is important to understand both the contribution of physical attributes from the surfaces of the materials and the perceptions that are involved in the haptic interaction. (2) Methods. A series of 16 wrinkled surfaces consisting of two similar materials of different elastic modulus and 8 different wrinkle wavelengths were characterized in terms of surface roughness and tactile friction coefficient. Sixteen participants scaled the perceived Roughness and Slipperiness of the surfaces using free magnitude estimation. Friction experiments were performed both by participants and by a trained experimenter with higher control. (3) Results and discussion. The trends in friction properties were similar for the group of participants performing the friction measurements in an uncontrolled way and the experiments performed under well-defined conditions, showing that the latter type of measurements represent the general friction properties well. The results point to slipperiness as the key perception dimension for textures below 100 μm and roughness above 100 μm. Furthermore, it is apparent that roughness and slipperiness perception of these types of structures are not independent. The friction is related to contact area between finger and material. Somewhat surprising was that the material with the higher elastic modulus was perceived as more slippery. A concluding finding was that the flat (high friction) reference surfaces were scaled as rough, supporting the theory that perceived roughness itself is a multidimensional construct with both surface roughness and friction components.
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| 17. |
- Attard, P, et al.
(författare)
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Dynamic surface force measurement. I. van der Waals collisions
- 1999
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Ingår i: Review of Scientific Instruments. - 0034-6748 .- 1089-7623. ; 69, s. 3852-3866
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical calculations and experimental measurements are used to show that hitherto neglected inertial effects can be significant in computer- controlled surface force measurement devices such as the atomic force microscope. The problem is analyzed in detail for the case of the van der Waals attraction in air. It is demonstrated that equating the cantilever deflection to the surface force systematically underestimates the magnitude of the surface force, increasingly so as the speed of approach is increased. It is also shown that the surface separation becomes lost at high accelerations due to a dynamic uncoupling of the cantilever deflection and angle. The effects of elastic deformation of the bodies are taken into account, including the collision-induced elastic vibrations in the solids. Experimental data are obtained for the van der Waals attraction and collision of glass surfaces in air using the measurement and analysis of surface forces device. All of the effects found in the theoretical calculations are identified in the experimental data.
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| 18. |
- Badal Tejedor, Maria, et al.
(författare)
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Tablet mechanics depend on nano and micro scale adhesion, lubrication and structure
- 2015
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Ingår i: International Journal of Pharmaceutics. - : Elsevier. - 0378-5173 .- 1873-3476. ; 486:1-2, s. 315-323
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Tidskriftsartikel (refereegranskat)abstract
- Tablets are the most convenient form for drug administration. However, despite the ease of manufacturing problems such as powder adhesion occur during the production process. This study presents surface and structural characterization of tablets formulated with commonly used excipients (microcrystalline cellulose (MCC), lactose, mannitol, magnesium (Mg) stearate) pressed under different compaction conditions. Tablet surface analyses were performed with scanning electron microscopy (SEM), profilometry and atomic force microscopy (AFM). The mechanical properties of the tablets were evaluated with a tablet hardness test. Local adhesion detected by AFM decreased when Mg stearate was present in the formulation. Moreover, the tablet strength of plastically deformable excipients such as MCC was significantly decreased after addition of Mg stearate. Combined these facts indicate that Mg stearate affects the particle-particle bonding and thus elastic recovery. The MCC excipient also displayed the highest hardness which is characteristic for a highly cohesive material. This is discussed in the view of the relatively high adhesion found between MCC and a hydrophilic probe at the nanoscale using AFM. In contrast, the tablet strength of brittle materials like lactose and mannitol is unaffected by Mg stearate. Thus fracture occurs within the excipient particles and not at particle boundaries, creating new surfaces not previously exposed to Mg stearate. Such uncoated surfaces may well promote adhesive interactions with tools during manufacture.
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| 19. |
- Brumer, Harry, et al.
(författare)
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Cross-Linking Involving a Polymeric Carbohydrate Material
- 2005
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Patent (populärvet., debatt m.m.)abstract
- The present invention relates to a method of cross-linking a polymeric carbohydrate material with a second material by means of a soluble carbohydrate polymer and a crosslinking agent. The present invention furthermore relates to the resulting cross-linked material, to uses of the cross-linked material, as well as to a kit comprising the soluble carbohydrate polymer and the cross-linking agent.
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| 20. |
- Claesson, Per M, et al.
(författare)
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Measuring interactions between surfaces
- 2002
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Ingår i: Handbook of Applied Colloid and Surface Chemistry. - Chichester, Weinheim : Wiley. - 0471490830 ; , s. 383-414
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Bokkapitel (refereegranskat)
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| 21. |
- Feiler, A., et al.
(författare)
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Atomic force microscopy measurements of adsorbed polyelectrolyte layers. 1. Dynamics of forces and friction
- 2003
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:10, s. 4173-4179
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of surface forces and friction between silica substrates bearing adsorbed layers acrylamide-1% [3-(2-methylpropionamide)propyl]trimethyl ammonium chloride (AM-MAPTAC) was examined using atomic force microscopy. The cationic polymer had a large molecular weight (900 000) and a very low charge density (1% MAPTAC units). The force curves in the presence of adsorbed polyelectrolyte showed a very long range repulsive interaction and large deformation on compression typical of electrosteric interactions and consistent with the expected adsorption profile. There was also a strong dependence on the scan rate with increased repulsion during approach and increased attraction during separation as the scan rate increased. The hysteresis was attributed entirely to a hydrodynamic interaction induced by the polyelectrolyte. At slow enough scan rates, the hysteresis between approach and retract curves was absent. The friction force measurements were sensitive to both applied load and scan rate. With increasing applied load, a critical load was apparent, above which the friction force increased. Upon decrease of the load, the friction force remained higher than that before the yield point, suggesting a metastable deformation of the polymer layer. In addition, the friction coefficient increased with increasing scan rate. At low scan rates the friction coefficient was lower than the bare surfaces, whereas at high scan rates the friction coefficient was significantly larger that obtained than for the bare surfaces. Subsequent force curves taken after friction measurements confirm that a permanent change in the polyelectrolyte layer had occurred. The magnitude of the repulsive interaction was reduced to about half of its original force.
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| 22. |
- Gebbie, Matthew A., et al.
(författare)
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Long range electrostatic forces in ionic liquids
- 2017
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 53:7, s. 1214-1224
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids are pure salts that are liquid under ambient conditions. As liquids composed solely of ions, the scientific consensus has been that ionic liquids have exceedingly high ionic strengths and thus very short Debye screening lengths. However, several recent experiments from laboratories around the world have reported data for the approach of two surfaces separated by ionic liquids which revealed remarkable long range forces that appear to be electrostatic in origin. Evidence has accumulated demonstrating long range surface forces for several different combinations of ionic liquids and electrically charged surfaces, as well as for concentrated mixtures of inorganic salts in solvent. The original interpretation of these forces, that ionic liquids could be envisioned as “dilute electrolytes,” was controversial, and the origin of long range forces in ionic liquids remains the subject of discussion. Here we seek to collate and examine the evidence for long range surface forces in ionic liquids, identify key outstanding questions, and explore possible mechanisms underlying the origin of these long range forces. Long range surface forces in ionic liquids and other highly concentrated electrolytes hold diverse implications from designing ionic liquids for energy storage applications to rationalizing electrostatic correlations in biological self-assembly.
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| 23. |
- Haigh, Daisy B., et al.
(författare)
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The METTL3 RNA Methyltransferase Regulates Transcriptional Networks in Prostate Cancer
- 2022
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Ingår i: Cancers. - : MDPI. - 2072-6694. ; 14:20
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Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer (PCa) is a leading cause of cancer-related deaths and is driven by aberrant androgen receptor (AR) signalling. For this reason, androgen deprivation therapies (ADTs) that suppress androgen-induced PCa progression either by preventing androgen biosynthesis or via AR signalling inhibition (ARSi) are common treatments. The N6-methyladenosine (m6A) RNA modification is involved in regulating mRNA expression, translation, and alternative splicing, and through these mechanisms has been implicated in cancer development and progression. RNA-m6A is dynamically regulated by the METTL3 RNA methyltransferase complex and the FTO and ALKBH5 demethylases. While there is evidence supporting a role for aberrant METTL3 in many cancer types, including localised PCa, the wider contribution of METTL3, and by inference m6A, in androgen signalling in PCa remains poorly understood. Therefore, the aim of this study was to investigate the expression of METTL3 in PCa patients and study the clinical and functional relevance of METTL3 in PCa. It was found that METTL3 is aberrantly expressed in PCa patient samples and that siRNA-mediated METTL3 knockdown or METTL3-pharmacological inhibition significantly alters the basal and androgen-regulated transcriptome in PCa, which supports targeting m6A as a novel approach to modulate androgen signalling in PCa.
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| 24. |
- Hansson, Petra M., et al.
(författare)
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Robust Hydrophobic Surfaces Displaying Different Surface Roughness Scales While Maintaining the Same Wettability
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:13, s. 8153-8159
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Tidskriftsartikel (refereegranskat)abstract
- A range of surfaces coated with spherical silica particles, covering the size range from nanometer to micrometer, have been produced using Langmuir-Blodgett (LB) deposition. The particles were characterized both in suspension and in the Langmuir trough to optimize the surface preparation procedure. By limiting the particle aggregation and surface layer failures during the preparation steps, well-defined monolayers with a close-packed structure have been obtained for all particle sizes. Thus, this procedure led to structured surfaces with a characteristic variation in the amplitude and spatial roughness parameters. In order to obtain robust surfaces, a sintering protocol and an AFM-based wear test to determine the stability of the deposited surface layer were employed. Hydrophobization of the LB films followed by water contact angle measurements showed, for all tested particle sizes, the same increase in contact angle compared to the contact angle of a flat hydrophobic surface. This indicates nearly hexagonal packing and gives evidence for nearly, complete surface wetting of the surface features.
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| 25. |
- Hjalmarsson, Nicklas, et al.
(författare)
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Switchable long-range double layer force observed in a protic ionic liquid
- 2017
-
Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 53:3, s. 647-650
-
Tidskriftsartikel (refereegranskat)abstract
- A repulsive double layer force has been measured for ethylammonium nitrate (EAN) at 373 K and 393 K, which is absent at lower temperatures. This temperature-tuneable change in behaviour is the opposite of recent observations which challenge traditional views of ionicity. This finding thus widens the debate about the very nature of ionic liquids.
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| 26. |
- Imae, T, et al.
(författare)
-
Forces between two glass surfaces with adsorbed hexadecyltrimethylammonium salicylate
- 2000
-
Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 16, s. 1937-1942
-
Tidskriftsartikel (refereegranskat)abstract
- Forces have been measured for hexadecyltrimethylammonium salicylate (C16TASal) layers on glass beads. During the inward process, hydrophobic attraction occurred at lower adsorption of C16TASal and electrostatic repulsion interactions happened at higher adsorption. While the jump-in phenomenon was observed for solutions of concentrations below the critical micelle concentration (cmc = 0.15 mM), the step-in phenomenon was characteristic for solutions at the cmc and above the cmc, suggesting the push-out of adsorbed C16TASal layers and/or inserted micelles. The remarkable pull-off phenomenon on the outward process occurred for all solutions, indicating a strong interaction between C16TASal molecules. For aqueous 0.15 mM C16TASal solutions of various NaSal concentrations, on the inward process, the electrostatic repulsive interaction decreased with adding NaSal. This is due to the electrostatic shielding by salt excess. The height of the force wall on the inward process reached a maximum at 0.01 M NaSal, but the interlocking between molecules on two surfaces during the outward process was minimized at 0.1 M NaSal. These tendencies, which are different from that of the electrostatic repulsion interaction, imply the strong cohesion between adsorbed C16TASal layers.
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| 27. |
- Jin, R., et al.
(författare)
-
Bioinspired Self-Assembled 3D Patterned Polymer Textures as Skin Coatings Models : Tribology and Tactile Behavior
- 2020
-
Ingår i: Biotribology. - : Elsevier Ltd. - 2352-5738. ; 24
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that during evolution, specific surface patterns emerged (e.g., on lotus leaves and butterfly wings) endowed with many remarkable surface properties (superhydrophobicity, vibrant structural color, delicate textures, etc.). In order to obtain these natural effects in cosmetics, we look for ways to transfer topographic patterns in coatings and treatments. Textured polymer surfaces were studied to explore their friction properties on the microscale and possible correlations with human tactile friction on the macroscale. We have chosen self-assembling block and random copolymers as model systems to prepare reliable biomimetic films with different micrometer and nanometer scale randomly patterned and randomly rough surfaces. The surface texture of the films was characterized by atomic force microscopy (AFM), and their tribological (friction) properties were studied with a surface forces apparatus (SFA) at a low sliding speed of 3 μm/s and at a speed of 10 cm/s relevant to realistic applications. The results are evaluated in terms of polymer segment mobility, interpenetration, entanglement and relaxation at interfaces, surface texture as described by roughness parameters, and interlocking of asperities. A stiction spike (static friction) was commonly found for the randomly patterned glassy polymer films. Random roughness patterns made from semi-crystalline polymers above their Tg gave high friction at low speed, but their friction coefficients were reduced at high speed due to less time for local entanglement and relaxations. The friction response of one of them was also affected differently by humidity than that of glassy polymer films. Tactile friction measurements with a human finger sliding against the polymer films revealed that the textures also provided differences at the macroscale, although the dynamic changes possibly due to lipid transfer, occlusion of moisture and/or damage of the films makes it difficult to draw robust conclusions. Finally, as an example, it is shown that these textures can be transferred to a soft elastomeric skin mimic substrate. This study introduces the concept of surface patterning by self-assembly to deliver tactile sensorial properties in coatings.
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| 28. |
- Mizuno, Hiroyasu, et al.
(författare)
-
Adhesive properties and sacrificial bonds in gastroliths of red-clawlobster measured by colloidal probe atomic force microscopy
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The adhesive properties of gastroliths of red claw lobsters (Cherax quadricarinatus) have been quantified using colloidal probe atomic force microscopy. Sequential detachment and large adhesion energies where observed between native gastrolith substrates and colloidal probes consisting of microparticles of heavily demineralized gastrolith that consists primarily of chitin and calcium carbonate hemispheres. The sequential detachment behavior was absent when the soluble proteins have been removed from gastrolith substrates and the adhesive energy is reduced by more than two orders of magnitude. The sacrificial bonds that provide the large adhesion energies were inferred to multifunctional gastrolith proteins that are able to bind to both chitin and calcium carbonate.
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| 29. |
- Mizuno, Hiroyasu, et al.
(författare)
-
Friction measurement between polyester fibres using the fibre probe SPM
- 2006
-
Ingår i: Australian journal of chemistry (Print). - 0004-9425 .- 1445-0038. ; 59, s. 390-393
-
Tidskriftsartikel (refereegranskat)abstract
- An SPM has been used to measure frictional interactions between two crossed fibres for the first time. The preparation of the surfaces is briefly described, but the crucial element is that the fibre attached to the AFM cantilever is glued parallel to the long axis. The fibres consist of polyester and frictional forces were measured both in air and solutions of cationic surfactant C(14)TAB. The friction coefficients reduce markedly with increasing concentration of surfactant which is ascribed to the formation of a boundary lubricating film between the surfaces. On removal of the solution, the subsequent friction coefficient in air was reduced by more than a factor of two compared to its value before immersion.
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| 30. |
- Plunkett, M. A., et al.
(författare)
-
Adsorption of pNIPAM layers on hydrophobic gold surfaces, measured in situ by QCM and SPR
- 2003
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:17, s. 6837-6844
-
Tidskriftsartikel (refereegranskat)abstract
- In situ surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) measurements have been employed to measure the adsorption kinetics and absolute adsorbed amount of the poly(N-isopropyl acrylamide) (pNIPAM) from bulk aqueous solution onto a hydrophobized gold substrate. The adsorption was carried out at 31 degreesC, which is just below the lower critical solution temperature of pNIPAM in water. We find that the shift in the coupling angle of the surface plasmon (proportional to the optical thickness) and the shift in the resonance frequency of the quartz crystal (proportional to the acoustic thickness) increase in parallel for most of the adsorption. Also, the change of dissipation is proportional to the change in frequency. These observations suggest that the buildup of the polymer layer proceeds via growth in thickness rather than by densification of a layer with constant thickness. We interpret this finding in the sense that the dense high-temperature phase wets the hydrophobic gold surface. The wetting layer has a fixed density and grows in thickness. In addition, the QCM has been used to study the temperature-induced conformational change for pNIPAM around the critical temperature. It was found that the technique was able to monitor additional adsorption that occurs when crossing the critical point, which was due to bulk phase separation. Desorption was also noted when crossing the critical point from the opposite direction, and for the given system the process was entirely reversible.
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| 31. |
- Plunkett, M. A., et al.
(författare)
-
Atomic force microscopy measurements of adsorbed polyelectrolyte layers. 2. Effect of composition and substrate on structure, forces, and friction
- 2003
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:10, s. 4180-4187
-
Tidskriftsartikel (refereegranskat)abstract
- An investigation on the effect of the conformation of preadsorbed polyelectrolyte layers of acrylamide-1% [3-(2-methylpropionamide)propyl]trimethylammonium chloride on the normal and lateral interactions between surfaces has been conducted. It was shown that when bridging mechanisms increased the adhesion, huge increases in the friction were also seen. When the polymer adsorbed in an extended layer, it resulted in a steric repulsion in the direction normal to the interface. However, the resulting friction measurements were shown to be far more complicated. For example, in cases where the integrity of the polymer layer was maintained under compression, the layer was able to act as a lubricant; however when the layer integrity was affected by the load and shear rate, then friction increased due to energy losses resulting, from disrupting the polymer conformation. The conformation was controlled by varying both the polymer charge density and the nature of the surface. The interaction between the polyelectrolyte and gold proved to be significantly stronger than that with silica, rendering the polymer layer more resistant to damage under shear and, consequently, a significantly different friction-load relationship. The dynamics of the interactions were also investigated and were highly dependent on the polyelectrolyte-surface interaction. As an aside, a novel observation of interference effects between cantilever and substrate is also made.
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| 32. |
- Plunkett, M. A., et al.
(författare)
-
Dynamic adhesion of grafted polymer surfaces as studied by surface force measurements
- 2002
-
Ingår i: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 16:7, s. 983-996
-
Tidskriftsartikel (refereegranskat)abstract
- Surface force experiments have been carried out to investigate the dynamics of adhesion for grafted polymer-coated glass spheres in a solvent. The quality of solvent has been varied both by changing the relative concentrations in a mixed solvent system and by variations in temperature in order to investigate the effect on the measured adhesion. Under very poor solvent conditions (far from theta conditions) there is a contact time dependence of the magnitude of the adhesion, that can be explained in terms of polymer interpenetration. This interpenetration is consistent with the diffusion following primitive path fluctuation dynamics. An increase in the maximum applied load leads to a decrease in adhesion which is attributed to a slower diffusion rate due to squeezing out of the solvent from the contact zone. Under slightly poor solvent conditions (near-theta conditions), any polymer interdiffusion is found to be rapid on the experimental time frame. In this case the adhesion is strongly dependent on the separation rate, which is interpreted in terms of viscoclastic losses at the crack tip.
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| 33. |
- Plunkett, M. A., et al.
(författare)
-
Surface forces and characterization of glass surfaces bearing grafted polymers : solvent dependence
- 2002
-
Ingår i: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 16:7, s. 965-981
-
Tidskriftsartikel (refereegranskat)abstract
- The interactions between two glass surfaces bearing grafted polymer brushes of poly(12-hydroxystearic acid) (PHS) have been controlled by altering the solvent quality. The graft density was obtained through XPS and the solvent used was a mixture of ethanol and heptane, which was varied from good to poor solvency conditions by either a change of the relative concentrations of the two solvents, or by altering the temperature. The system is shown to be remarkably sensitive to the solvency conditions around the theta position. It was also shown that hydrodynamic forces could be accurately and routinely accounted for in systems where the forces were monotonically repulsive.
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| 34. |
- Poptoshev, E, et al.
(författare)
-
Comparison of model surfaces for cellulose interactions; elevated pH
- 2000
-
Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 116, s. 79-83
-
Tidskriftsartikel (refereegranskat)abstract
- Two different substrates have been used to measure interaction forces between cellulose and between cellulose and glass at normal and high pH. Forces between microspheres of cellulose (r=20-30 µm) have been measured using the colloidal probe atomic force microscopy technique. Interactions between Langmuir-Blodgett cellulose films on a hydrophobised mica substrate and a glass sphere have been determined with the noninterferometric surface force apparatus. Also, the interaction between two identical Langmuir-Blodgett cellulose films determined with the interferometric surface force apparatus is given for comparison. At low pH (5.5-6) the interaction at large separations in both systems is characterised by a double-layer repulsion with an electrosteric contribution dominating the shorter-range regime. At pH 10, the Langmuir-Blodgett cellulose film swells considerably, which generates a long-range steric repulsion. In many cases several inward steps have been observed in the force-distance curves. We attribute this to a sudden partial collapse of the swollen cellulose film. After initial compression of the steric layer (upon consecutive force runs) the long-range interaction is again dominated by a double-layer force. In contrast, measurements between two cellulose spheres have shown no excessive swelling. Only a limited increase (from about 10 nm to about 20 nm per surface) of the range of the electrosteric repulsion has been found at pH 10. The force at longer distances is in good agreement with the Poisson-Boltzmann theory, with the surface potential increasing with pH as expected.
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| 35. |
- Poptoshev, E., et al.
(författare)
-
Surface forces in aqueous polyvinylamine solutions. 2. Interactions between glass and cellulose
- 2000
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:4, s. 1987-1992
-
Tidskriftsartikel (refereegranskat)abstract
- The forces acting between one surface coated with Langmuir-Blodgett cellulose films and one glass surface have been measured using the MASIF surface force technique. This study is mainly concerned with the effects due to addition of cationic polyvinylamine and changes in ionic strength. The results have implications for the interactions between cellulose and mineral surfaces in the papermaking process. The cellulose surface is weakly negatively charged at pH 5.5-6.0. Polyvinylamine adsorbs to both glass and cellulose surfaces, which first causes charge neutralization and subsequently a charge reversal upon increasing the polymer concentration. The cellulose films swell upon immersion in aqueous solutions as evidenced by the appearance of a short-range steric force barrier. The dynamics of the swelling process was found to be dependent on the ionic strength of the solution. It was found that an increased ionic strength accelerates the swelling, which can be attributed to an increase in surface charge density and hence an increase in the short-range repulsion between individual cellulose chains. The results obtained in this study are consistent with those obtained for the interaction between two glass surfaces in polyvinilamine solutions as described in a previous report. However, the long-range (bridging) attraction observed between two glass surfaces immersed in the polyvinylamine solution was absent between one glass and one cellulose surface. We attribute this to the lower surface charge density of the cellulose surface.
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| 36. |
- Poptoshev, E., et al.
(författare)
-
Surface forces in aqueous polyvinylamine solutions. I. Glass surfaces
- 1999
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 15:22, s. 7789-7794
-
Tidskriftsartikel (refereegranskat)abstract
- A noninterferometric surface force apparatus has been used to measure interactions between glass spheres in dilute aqueous polyvinylamine solutions at two different salt concentrations. Close to the substrate charge neutralization point, an attractive interaction is present mainly because of bridging of the extending polymer tails. Additional adsorption leads to an overcompensation of the glass negative surface charge, and the interaction at this point is dominated by a long-range double-layer repulsion. The results from fitting the Derjaguin-Landau-Verwey-Overbeek theory to the measured force curves demonstrate that the degree of overcompensation increases with polyelectrolyte concentration and increasing ionic strength of the solution (addition of indifferent electrolyte). An increase in ionic strength results in the screening of the electrostatic forces which leads to: (i) a reduced free energy cost of creating a charged interface, (ii) a decreased repulsion between protonated amine groups along the polymer backbone and a corresponding increased chain flexibility, (iii) a reduced electrostatic attraction between the polyelectrolyte and the surface. The first effect is apparently is the most important in the present case.
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| 37. |
- Ralston, J., et al.
(författare)
-
Atomic force microscopy and direct surface force measurements - (IUPAC technical report)
- 2005
-
Ingår i: Pure and Applied Chemistry. - : Walter de Gruyter GmbH. - 0033-4545 .- 1365-3075. ; 77:12, s. 2149-2170
-
Forskningsöversikt (refereegranskat)abstract
- The atomic force microscope (AFM) is designed to provide high-resolution (in the ideal case, atomic) topographical analysis, applicable to both conducting and nonconducting surfaces. The basic imaging principle is very simple: a sample attached to a piezoelectric positioner is rastered beneath a sharp tip attached to a sensitive cantilever spring. Undulations in the surface lead to deflection of the spring, which is monitored optically. Usually, a feedback loop is employed, which holds the spring deflection constant, and the corresponding movement of the piezoelectric positioner thus generates the image. From this it call be seen that the scanning AFM has all the attributes necessary for the determination of surface and adhesion forces; a sensitive spring to determine the force, a piezoelectric crystal to alter the separation of the tip and surface, which if sufficiently well-calibrated also allows the relative separation of the tip and surface to be calculated. One can routinely quantify both the net Surface force (and its separation dependence) as the probe approaches the sample, and any adhesion (pull-off) force on retraction. Interactions in relevant or practical systems may be studied, and, in such cases, a distinct advantage of the AFM technique is that a particle of interest can be attached to the end of the cantilever and the interaction with a sample of choice can be studied, a method often referred to as colloid probe microscopy. The AFM, or, more correctly, the scanning probe microscope, call thus be used to measure surface and frictional forces, the two foci of this article. There have been a wealth of force and friction measurements performed between all AFM tip and a Surface, and many of the calibration and analysis issues are identical to those necessary for colloid probe work. We emphasize that this article confines itself primarily to elements of colloid probe measurement using the AFM.
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| 38. |
- Rutland, M, et al.
(författare)
-
Calcium soaps in flotation deinking; Fundamental studies using surface force and coagulation techniques
- 1997
-
Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 125, s. 33-46
-
Tidskriftsartikel (refereegranskat)abstract
- The surface force technique was shown to give useful information concerning the interaction of fatty acid flotation collectors and Ca2+ activator with a hydroxylated mica substrate at high pH. Since the surface of ink particles are enriched mainly by hydroxyl groups from natural resins, these experiments enabled some details of the fundsmental mechanisms involved in deinking flotation to be illucinated. The preliminary results (carried out at relatively low Ca2+ and fatty acid concentrations) may be summarised as follows; (a) At pH >10, the hydroxylated surface generated a long range DLVO double_x001E_layer repulsion and the electrical potential at the mica/electrolyte interface could be estimated. However, at short distances (15 Å from mica contact) a repulsive non-DLVO hydration barrier were detected due to adsorbed Na2+. (b) On addition of CaCl2, the Na2+ was exchanged by less strongly hydrated Ca2+ resulting in the elimination of the hydration forces and mica-mica contact. On addition of fatty acid, no change in the force profile was detected suggesting no Ca2+ was removal from the surface and there was no evidence of calcium soap formation in the surface region. This result implies that the Ca2+ does not induce a bridging mechanism in the presence of fatty acid (below the calcium soap precipitation level). In fact, the Ca2+ ions could only operate as bridging agents if they can specific bind to the surface as well as the carboxylated fatty acid. The "Ca2+ dehydration destabilization mechanism" was verified by coagulation studies with quartz suspensions. At higher fatty acid and Ca2+ concentrations, calcium soap was precipitated in bulk solution. It was suggested that microencapsulation of the ink particles with hydrophobic species can only occur through heterocoagulation with the bulk precipitated calcium soap particles.
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| 39. |
- Rutland, M, et al.
(författare)
-
pH-dependent interactions of mica surfaces in aqueous dodecylammonium/dodecylamine solutions
- 1992
-
Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 8, s. 176-183
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption of a hydrolyzable surfactant, dodecylammonium chloride, and interactions between layers thereof, has been studied at a surfactant concentration of 10-4 M as a function of pH using the surface force apparatus. At low pH the surfaces undergo charge reversal as dodecylammonium ions adsorb to form a sparse monolayer. At pH 8-9, adsorption of neutral dodecylamine molecules becomes important, rendering the monolayer more compact with a thickness close to the length of an extended molecule. A hydrophobic attraction is observed between the surfactant monolayers. At pH 9.5-10.3, a bilayer forms on each surface. The double layer force decreases gradually with incrasing pH and disappears at pH 10.3. At this and slightly higher pH values a multilayer gradually builds up on the surface. At pH values around 12 the multilayer buildup is prevented by a recharging of the adsorbed layer. Both the adsorption behavior and the interactions between the layers are reversible with respect to changes in the pH. The structure of the adsorbed surfactant layer on mica is compared to that on other surfaces.
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| 40. |
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| 41. |
- Ryman-Tubb, Toby, et al.
(författare)
-
Comparative pathology of dog and human prostate cancer
- 2022
-
Ingår i: Veterinary medicine and science. - : John Wiley & Sons. - 2053-1095. ; 8:1, s. 110-120
-
Tidskriftsartikel (refereegranskat)abstract
- Though relatively rare in dogs, prostate cancer (PCa) is the most common non-cutaneous cancer in men. Human and canine prostate glands share many functional, anatomical and physiological features. Due to these similarities, canine PCa has been proposed as a model for PCa in men. PCa is typically androgen-dependent at diagnosis in men and for this reason, androgen deprivation therapies (ADT) are important treatments for advanced PCa in men. In contrast, there is some evidence that PCa is diagnosed more commonly in castrate dogs, at which point, limited therapeutic options are available. In men, a major limitation of current ADT is that progression to a lethal and incurable form of PCa, termed castrate-resistant prostate cancer (CRPC), is common. There is, therefore, an urgent need for a better understanding of the mechanism of PCa initiation and progression to CRPC to enable the development of novel therapeutic approaches. This review focuses on the functional, physiological, endocrine and histopathological similarities and differences in the prostate gland of these species. In particular, we focus on common physiological roles for androgen signalling in the prostate of men and dogs, we review the short- and longer-term effects of castration on PCa incidence and progression in the dog and relate how this knowledge may be relevant to understanding the mechanisms of CRPC in men.
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| 42. |
- Skedung, Lisa, et al.
(författare)
-
A Curly Q : Is Frizz a Matter of Friction?
- 2021
-
Ingår i: Perception. - : SAGE Publications. - 0301-0066 .- 1468-4233. ; 50:8, s. 728-732
-
Tidskriftsartikel (refereegranskat)abstract
- The oft discussed and fretted over environmental influences on hair have led to a popular consensus which suggests that elevated temperature and humidity lead to frizzier, wilder hair. However, few attempts at actually quantifying these effects have been made. Although frizziness is usually perceived visually, here the influence of variations in temperature and humidity on the tactile perception and friction of curly and straight hair were investigated. It is shown that changes in humidity may disproportionately affect perceived frizziness of curly hair by touch due to concurrent changes in the tactile friction.
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| 43. |
- Skedung, Lisa, et al.
(författare)
-
Feeling small : Exploring the Tactile Perception Limits
- 2013
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3, s. 2617-
-
Tidskriftsartikel (refereegranskat)abstract
- The human finger is exquisitely sensitive in perceiving different materials, but the question remains as to what length scales are capable of being distinguished in active touch. We combine material science with psychophysics to manufacture and haptically explore a series of topographically patterned surfaces of controlled wavelength, but identical chemistry. Strain-induced surface wrinkling and subsequent templating produced 16 surfaces with wrinkle wavelengths ranging from 300 nm to 90 mu m and amplitudes between 7 nm and 4.5 mu m. Perceived similarities of these surfaces (and two blanks) were pairwise scaled by participants, and interdistances among all stimuli were determined by individual differences scaling (INDSCAL). The tactile space thus generated and its two perceptual dimensions were directly linked to surface physical properties - the finger friction coefficient and the wrinkle wavelength. Finally, the lowest amplitude of the wrinkles so distinguished was approximately 10 nm, demonstrating that human tactile discrimination extends to the nanoscale.
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| 44. |
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| 45. |
- Stenler, S., et al.
(författare)
-
Micro-minicircle gene therapy : Implications of size on fermentation, complexation, shearing resistance, and expression
- 2014
-
Ingår i: Molecular Therapy Nucleic Acids. - : Elsevier BV. - 2162-2531. ; 3, s. e140-
-
Tidskriftsartikel (refereegranskat)abstract
- The minicircle (MC), composed of eukaryotic sequences only, is an interesting approach to increase the safety and efficiency of plasmid-based vectors for gene therapy. In this paper, we investigate micro-MC (miMC) vectors encoding small regulatory RNA. We use a construct encoding a splice-correcting U7 small nuclear RNA, which results in a vector of 650 base pairs (bp), as compared to a conventional 3600 bp plasmid carrying the same expression cassette. Furthermore, we construct miMCs of varying sizes carrying different number of these cassettes. This allows us to evaluate how size influences production, supercoiling, stability and efficiency of the vector. We characterize coiling morphology by atomic force microscopy and measure the resistance to shearing forces caused by an injector device, the Biojector. We compare the behavior of miMCs and plasmids in vitro using lipofection and electroporation, as well as in vivo in mice. We here show that when the size of the miMC is reduced, the formation of dimers and trimers increases. There seems to be a lower size limit for efficient expression. We demonstrate that miMCs are more robust than plasmids when exposed to shearing forces, and that they show extended expression in vivo.
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| 46. |
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| 47. |
- Stubenrauch, C., et al.
(författare)
-
Mixtures of n-dodecyl-beta-D-maltoside and hexaoxyethylene dodecyl ether : Surface properties, bulk properties, foam films, and foams
- 2010
-
Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686 .- 1873-3727. ; 155:1-2, s. 5-18
-
Tidskriftsartikel (refereegranskat)abstract
- Mixtures of the two non-ionic surfactants hexaoxyethylene dodecyl ether (C12E6) and n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) were studied with regard to surface properties, bulk properties, foam films, and foams. The reason for studying a mixture of an ethylene oxide (CiEj) and a sugar (C(n)G(m),) based surfactant is that despite being non-ionic, these two surfactants behave quite differently. Firstly, the physico-chemical properties of aqueous solutions of C(n)G(m) surfactants are less temperature-sensitive than those of CiEj solutions. Secondly, the surface charge density q(0) of foam films stabilized by C(n)G(m) surfactants is pH insensitive down to the so-called isoelectric point, while that of foam films stabilized by CiEj surfactants changes linearly with the pH. The third difference is related to interaction forces between solid surfaces. Under equilibrium conditions very high forces are needed to expel beta-C(12)G(2) from between thiolated gold surfaces, while for C12E6 low loads are sufficient. Fourthly, the adsorption of C12E6 and beta-C(12)G(2) on hydrophilic silica and titania, respectively, is inverted. While the surface excess of C12E6 is large on silica and negligible on titania, beta-C(12)G(2) adsorbs very little on silica but has a large surface excess on titania. What is the reason for this different behaviour? Under similar conditions and for comparable head group sizes, it was found that the hydration of CiEj surfactants is one order of magnitude higher but on average much weaker than that of C(n)G(m) surfactants. Moreover, C(n)G(m) surfactants possess a rigid maltoside unit, while CiEj surfactants have a very flexible hydrophilic part. Indeed, most of the different properties mentioned above can be explained by the different hydration and the head group flexibilities. The intriguing question of how mixtures of CiEj and C(n)G(m) surfactants would behave arises organically. Thus various properties of C12E6 + beta-C(12)G(2) mixtures in aqueous solution have been studied with a focus on the 1:1 mixture. The results are compared with those of the single surfactants and are discussed accordingly.
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| 48. |
- Sun, Kangdi, et al.
(författare)
-
Insight into the assembly of lipid-hyaluronan complexes in osteoarthritic conditions
- 2023
-
Ingår i: Biointerphases. - : American Institute of Physics Inc.. - 1934-8630 .- 1559-4106. ; 18:2
-
Tidskriftsartikel (refereegranskat)abstract
- Interactions between molecules in the synovial fluid and the cartilage surface may play a vital role in the formation of adsorbed films that contribute to the low friction of cartilage boundary lubrication. Osteoarthritis (OA) is the most common degenerative joint disease. Previous studies have shown that in OA-diseased joints, hyaluronan (HA) not only breaks down resulting in a much lower molecular weight (MW), but also its concentration is reduced ten times. Here, we have investigated the structural changes of lipid-HA complexes as a function of HA concentration and MW to simulate the physiologically relevant conditions that exist in healthy and diseased joints. Small angle neutron scattering and dynamic light scattering were used to determine the structure of HA-lipid vesicles in bulk solution, while a combination of atomic force microscopy and quartz crystal microbalance was applied to study their assembly on a gold surface. We infer a significant influence of both MW and HA concentrations on the structure of HA-lipid complexes in bulk and assembled on a gold surface. Our results suggest that low MW HA cannot form an amorphous layer on the gold surface, which is expected to negatively impact the mechanical integrity and longevity of the boundary layer and could contribute to the increased wear of the cartilage that has been reported in joints diseased with OA. © 2023 Author(s).
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| 49. |
- Thormann, Esben, et al.
(författare)
-
Embedded proteins and sacrificial bonds provide the strong adhesive properties of gastroliths
- 2012
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 4:13, s. 3910-3916
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Tidskriftsartikel (refereegranskat)abstract
- The adhesive properties of gastroliths from a freshwater crayfish (Cherax quadricarinatus) were quantified by colloidal probe atomic force microscopy (AFM) between heavily demineralized gastrolith microparticles and gastrolith substrates of different composition. Combined AFM and transmission electron microscopy studies demonstrated that the sequential detachment and large adhesion energies that characterise the adhesive behaviour of a native gastrolith substrate are dominated by sacrificial bonds between chitin fibres and between chitin fibres and CaCO3. The sacrificial bonds were shown to be strongly related to the gastrolith proteins and when the majority of these proteins were removed by ethylenediaminetetraacetic acid (EDTA), the sequential detachment disappeared and the adhesive energy was reduced by more than two orders of magnitude.
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