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| 3. |
- Höök, Fredrik, 1966, et al.
(author)
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Characterization of PNA and DNA Immobilization and Subsequent Hybridization with DNA Using Acoustic-Shear-Wave Attenuation Measurements
- 2001
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 17:26, s. 8305-8312
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Journal article (peer-reviewed)abstract
- We report here how the quartz crystal microbalance with dissipation monitoring (QCM-D) technique, simultaneously measuring changes in the induced energy dissipation, D (cf. viscoelastic properties), and the frequency, f (cf. coupled mass), can be used to characterize the bound state of single-stranded peptide nucleic acid (PNA) and deoxyribose nucleic acid (DNA) in relation to their ability to function as selective probe(s) for fully complementary and single-mismatch DNA. The possibility to use the QCM-D technique for detection of binding kinetics and structural differences in the formed duplexes is also presented. We found that thiol-PNA and thiol-DNA attached via a sulfur group directly on a bare-gold surface are less efficient as probes for DNA than are biotin-PNA and biotin-DNA, coupled on top of a two-dimensional (2-D) arrangement of streptavidin, formed on a biotinylated phospholipid bilayer on a SiO2 surface. The fully complementary and singly mismatched DNA oligomers hybridize with the immobilized PNA and DNA. A single mismatch is discriminated via a significant difference in the binding and dissociation kinetics, demonstrating a high selectivity and thus successful immobilization of functional single strands. The observed ratios between hybridization-induced energy dissipation (DeltaD) and the frequency shift (Deltaf) made it possible to discriminate thiol-PNA directly attached to a gold surface from biotin-PNA coupled to the streptavidin 2-D arrangement, where the former were shown to be inefficient for detecting subsequent hybridization. Structural differences of the immobilized layers composed of biotin-PNA-DNA and biotin-DNA-DNA were clearly reflected by the DeltaD and Deltaf response.
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| 4. |
- Kamp, Carl Justin, 1982, et al.
(author)
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Nanofabricated catalyst particles for the investigation of catalytic carbon oxidation by oxygen spillover
- 2017
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 33:20, s. 4903-4912
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Journal article (peer-reviewed)abstract
- The catalytic oxidation of carbon by molecular oxygen was studied using C/Pt, Pt/C, Pt/Al2O3/C, Pt/CeO2/C, Al2O3/C and CeO2/C model samples prepared by hole-mask colloidal lithography. By this technique the degree of contact between platinum and carbon was controlled with high precision. The oxidation of carbon was monitored using atomic force microscopy and scanning electron microscopy. The results show that Pt in direct contact with carbon catalyzes the oxidation of carbon by spillover of dissociated oxygen from Pt to carbon. By physically separating Pt and carbon with a 10 nm thin spacer layer of Al2O3, the oxygen spillover was entirely blocked. However, through a corresponding spacer layer of CeO2, carbon oxidation was still observed, either by oxygen spillover from Pt to carbon or directly dissociated on the ceria, although at a slower rate compared to the case with no spacer layer between Pt and carbon.
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| 5. |
- Strömquist, Johan, 1967, et al.
(author)
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Ballistic motion and abstraction in dimer dissociation at surfaces: Cl-2 on K
- 1996
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In: Surface Science. - 0039-6028. ; 352:435-441, s. 7-
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Journal article (peer-reviewed)abstract
- Non-traditional dissociation dynamics at surfaces, with charge transfer and diabatic motion, is studied for the model system of Cl-2 molecules impinging on the metal K. Three-dimensional molecular dynamics on simple but physically reasonable potential-energy surfaces is used to investigate the final fates of the dissociation fragments (Cl, Cl-) of the molecular ion, Cl-2(-), that is formed by electron transfer (harpooning) to Cl-2 from the K surface. The model study demonstrates that both abstraction (emission of neutrals) and ballistic motion can result from dissociative chemisorption. Our qualitative reasoning has strong implications on other chemisorption systems, like O-2 on alkali and other metals and halogens on Si, e.g., a proposed explanation for ballistically moving O atoms on Al.
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| 6. |
- Wittung Stafshede, Pernilla, 1968, et al.
(author)
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Detection of point mutations in DNA by PNA-based quartz-crystal biosensor
- 2000
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 1873-4359 .- 0927-7757. ; 174:1-2, s. 269-273
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Journal article (peer-reviewed)abstract
- Currently there is an extensive search for biosensors for detecting genetic defects by hybridisation to immobilised oligonucleotides. A concept able to detect a single mismatch in a 15mer single-strand target of the p53 tumor suppresser gene is presented (a mutation found in many types of cancer cells). In this method, the unique hybridisation properties of the DNA mimic peptide nucleic acid (PNA) are combined with electronically detected mass and shear dissipation at the surface of a quartz crystal. Cysteine-labeled PNA efficiently immobilises on crystal-gold surface at 20 degrees C. At 60 degrees C, addition of complementary DNA results in a signal response corresponding to hybridisation between DNA and the PNA-covered surface, whereas addition of DNA differing in only one of the 15 bases gives no response at all.
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| 10. |
- Andersson, Ann-Sofie, et al.
(author)
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Cell adhesion on supported lipid bilayers
- 2003
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In: Journal of biomedical materials research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 64:4, s. 622-9
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Journal article (peer-reviewed)abstract
- The cell and protein repellent properties of supported phospholipid bilayer (SPB) membranes were investigated. The SPBs were prepared by vesicle adsorption on SiO(2) surfaces. The vesicles of phosphatidylcholine fuse and rupture, and form a supported bilayer covering the surface. We carried out cell culture experiments on several surfaces, including SPBs, using two types of epithelial cells to address the cell adhesional properties. The Quartz Crystal Microbalance Dissipation (QCM-D) technique was used to monitor the SPB formation and subsequent protein adsorption. Neither cell type adhered or proliferated on SiO(2) surfaces coated with SPBs, whereas both cell types adhered and proliferated on the three control surfaces of SiO(2), tissue culture glass, and TiO(2). The QCM-D measurements showed that about two orders of magnitude less mass adsorbed on a SPB surface compared to a TiO(2) surface, from serum-containing media (10% fetal bovine serum). The reduced adsorption on the SPB is a likely explanation for the nondetectable epithelial cell adhesion on the SPB surface. Biomembranes are therefore attractive candidate systems to achieve alternating cell-resistant and cell-interacting regions on surfaces, by including specific cell-binding proteins in the latter regions.
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| 11. |
- Andersson, Dag R., et al.
(author)
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A molecular beam scattering apparatus for surface chemiluminescence studies. Preliminary results for emission of excited K atoms.
- 1989
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Journal article (other academic/artistic)abstract
- A molecular beam scattering apparatus has been constructed for the study of surface chemiluminescence, i.e. the emission of light during a molecule-surface reaction. The apparatus consists of a beam forming stage designed for molecular and atomic chlorine, and a scattering chamber. The scattering chamber houses the sample, an alkali evaporation source, and a rotatable flange which holds the detectors; (i) the imaging optics of the photon detector, (ii) a mass spectrometer detector and (iii) a charged particle collector. The performance of the apparatus is demonstrated for a beam of chlorine molecules impinging on continuously evaporated or freshly evaporated potassium films. Intensity versus chlorine exposure and angular intensity distributions are presented for the K(4p ->4s) atomic line emission of the K+Cl$_2$ surface chemiluminescence spectrum.
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| 12. |
- Benkoski, JJ, et al.
(author)
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Light-activated desorption of photoactive polyelectrolytes from supported lipid bilayers
- 2005
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 38:9, s. 3852-3860
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Journal article (peer-reviewed)abstract
- Phospholipid vesicles and supported bilayers have emerged as a promising platform for the development of biorecognition devices. To expand the capabilities of such biochips, it becomes desirable to direct and control the assembly of lipid structures into more sophisticated architectures. As one step toward this goal, we demonstrate the photoregulated desorption of a new class of polymer from lipid bilayers. The neutral, hydrophobic polymer resides within the bilayer under mild pH and ambient conditions. However, it contains side groups that can undergo excited state proton transfer (ESPT). The polymer therefore behaves as a polyelectrolyte when exposed to IN light. With the ensuing increase in hydrophilicity, the molecule is spontaneously ejected from the bilayer. Quartz crystal microbalance measurements with dissipation monitoring (QCM-D) have recorded this process and have shown that a rapid buffer exchange during light exposure results in efficient removal of the polymer from the system. Three polymers were tested in all: a polyanion, a polyeation, and a polyzwitterion. A one-step approach to the synthesis of the monomer, performed under relatively mild reaction conditions, made it possible to synthesize each polymer in one step.
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| 16. |
- Bode, G.H., et al.
(author)
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Detection of peptide-based nanoparticles in blood plasma by ELISA
- 2015
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 10:5, s. Art. no. e0126136-
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Journal article (peer-reviewed)abstract
- Aims: The aim of the current study was to develop a method to detect peptide-linked nanoparticles in blood plasma. Materials & Methods: A convenient enzyme linked immunosorbent assay (ELISA) was developed for the detection of peptides functionalized with biotin and fluorescein groups. As a proof of principle, polymerized pentafluorophenyl methacrylate nanoparticles linked to biotin-carboxyfluorescein labeled peptides were intravenously injected in Wistar rats. Serial blood plasma samples were analyzed by ELISA and by liquid chromatography mass spectrometry (LC/MS) technology. Results: The ELISA based method for the detection of FITC labeled peptides had a detection limit of 1 ng/mL. We were able to accurately measure peptides bound to pentafluorophenyl meth-acrylate nanoparticles in blood plasma of rats, and similar results were obtained by LC/MS. Conclusions: We detected FITC-labeled peptides on pentafluorophenyl methacrylate nanoparticles after injection in vivo. This method can be extended to detect nanoparticles with different chemical compositions.
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| 17. |
- Briand, Elisabeth, 1979, et al.
(author)
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An OEGylated thiol monolayer for the tethering of liposomes and the study of liposome interactions
- 2010
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In: Talanta. - : Elsevier BV. - 0039-9140. ; 81:4-5, s. 1153-1161
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Journal article (peer-reviewed)abstract
- The aim of the present work is to develop a protocol for the specific immobilization of liposomes, via tethers, onto functionalized gold surfaces, and in addition to give one example for such a surface architecture All surface functionalization steps are charcerized and controlled First, mixed thiolate self-assembled monolayers (SAMs) prepared from COOH- and OCH3-terminated oligo(ethylene glycol) (OEG) alkane thiols were characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and by X-ray photoemission spectroscopy (XPS). The composition of the mixed SAMs was found to be close to that of the thiol solution. Next, grafting of biotin conjugated with an NH2-terminated OEG spacer (biotin-OEG-NH2) to the COOH groups via conventional amine coupling was optimized with respect to the COOH/OCH3 ratio of the SAM. The grafting of biotin-OEG-NH2 was assessed by monitoring the binding of neutravidin and albumin to the biotinylated surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by PM-RAIRS It was shown that a COOH/OCH3 ratio of around 0.3 was sufficient to saturate the SAMs with neutravidin. Finally, tethering of liposomes onto the neutravidin-terminated SAMs. was achieved. As an application example. of a close packed layer of tethered liposomes was exposed to the membrane-penetrating peptide melittin As monitored by QCM-D. the liposomes fused when interacting with the peptide and ruptured into an extended. supported lipid bilayer over the whole surface. In summary, the described surface modification has potential for the development of assays requiring tethered Intact liposomes, or tethered planar bilayers. Such surface architectures are especially important for the study of transmembrane proteins and peptides.
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| 18. |
- Briand, Elisabeth, 1979, et al.
(author)
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Chemical Modifications of Au/SiO2 Template Substrates for Patterned Biofunctional Surfaces
- 2011
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 27:2, s. 678-685
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Journal article (peer-reviewed)abstract
- The aim of this work was to create patterned surfaces for localized and specific biochemical recognition. For this purpose, we have developed a protocol for orthogonal and material-selective surface modifications of microfabricated patterned surfaces composed of SiO2 areas (100 mu m diameter) surrounded by Au. The SiO2 spots were chemically modified by a sequence of reactions (silanization using an amine-terminated silane (APTES), followed by amine coupling of a biotin analogue and biospecific recognition) to achieve efficient immobilization of streptavidin in a functional form. The surrounding Au was rendered inert to protein adsorption by modification by HS(CH2)(10)CONH-(CH2)(2)(OCH2CH2)(7)OH (thiol-OEG). The surface modification protocol was developed by testing separately homogeneous SiO2 and Au surfaces, to obtain the two following results: (i) SiO2 surfaces which allowed the grafting of streptavidin, and subsequent immobilization of biotinylated antibodies, and (ii) Au surfaces showing almost no affinity for the same streptavidin and antibody solutions. The surface interactions were monitored by quartz crystal microbalance with dissipation monitoring (QCM-D), and chemical analyses were performed by polarization modulation-reflexion absorption infrared spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS) to assess the validity of the initial orthogonal assembly of APTES and thiol-OEG. Eventually, microscopy imaging of the modified Au/SiO2 patterned substrates validated the specific binding of streptavidin on the SiO2/APTES areas, as well as the subsequent binding of biotinylated anti-rIgG and further detection of fluorescent rIgG on the functionalized SiO2 areas. These results demonstrate a successful protocol for the preparation of patterned biofunctional surfaces, based on microfabricated Au/SiO2 templates and supported by careful surface analysis. The strong immobilization of the biomolecules resulting from the described protocol is advantageous in particular for micropatterned substrates for cell-surface interactions.
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| 19. |
- Briand, Elisabeth, 1979, et al.
(author)
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Combined QCM-D and EIS study of supported lipid bilayer formation and interaction with pore-forming peptides
- 2010
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In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 135:2, s. 343-350
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Journal article (peer-reviewed)abstract
- A novel set-up combining the quartz crystal microbalance with dissipation monitoring technique (QCM-D) and electrochemical impedance spectroscopy (EIS) under flow conditions was successfully used to follow supported lipid bilayer (SLB) formation on SiO(2). This study demonstrates the simultaneous detection, in real time, of both the electrical and the structural properties of the SLB. The combination of the two techniques provided novel insights regarding the mechanism of SLB formation: we found indications for an annealing process of the lipid alkyl chains after the mass corresponding to complete bilayer coverage had been deposited. Moreover, the interaction of the SLB with the pore-forming toxin, gramicidin D (grD) was studied for grD concentrations ranging from 0.05 to 40 mg L(-1). Membrane properties were altered depending on the toxin concentration. For low grD concentrations, the electrical properties of the SLB changed upon insertion of active ion channels. For higher concentrations, the QCM-D data showed dramatic changes in the viscoelastic properties of the membrane while the EIS spectra did not change. AFM confirmed significant structural changes of the membrane at higher grD concentrations. Thus, the application of combined QCM-D and EIS detection provides complementary information about the system under study. This information will be particularly important for the continued detailed investigation of interactions at model membrane surfaces
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| 20. |
- Cardenas, J. F., et al.
(author)
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Light induced selective heating of nanostructured pyrolitic graphite surfaces investigated by Raman scattering
- 2013
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In: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 415, s. 232-236
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Journal article (peer-reviewed)abstract
- Nanostructured surfaces of highly oriented pyrolytic graphite (HOPG) were characterized by Raman spectroscopy. The disc-shape nanostructures similar to 110 nm high and with two different diameters similar to 147 and 217 nm are prepared on HOPG using hole-mask colloidal lithography and oxygen reactive ion etching. Significant roughening of the HOPG surface is introduced by the nano-fabrication process, but the nano-disc structures preserves their crystalline structure. Resonant light absorption results in selective heating of nanostructures, although the surrounding medium remains relatively unaffected. Temperature differences of up to 350 K were measured under irradiation with similar to 11 mW/mu m(2). Further increase of the light intensity leads to combustion of structures.
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| 21. |
- Cardenas, J. F., et al.
(author)
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Structural Raman Enhancement in Graphite Nano-Discs
- 2016
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781510601284 ; 9883, s. Article Number: 98830L-
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Conference paper (peer-reviewed)abstract
- Raman scattering in disc-shaped graphite nanostructures, etched out of bulk HOPG, are investigated using an excitation wavelength of 532 nm at different laser power. The G-band is fitted using two Lorentzian functions, G(L) and G(H). The difference of Raman shift between the two Lorentzian functions increase with laser power as a consequence of selective absorption and heating of the discs. Further, the G-band from the nanostructured HOPG reveal a Raman enhancement (R-E) of similar to 2.2 and similar to 1.5 for the components associated with the discs (G(L)) and the supporting substrate (G(H)), respectively. The quantitative agreement between the experimental results and performed finite difference time domain calculations make possible to conclude that electromagnetic energy penetrates considerably into the discs from the circular periphery probably due to multiple scattering. In addition, the dependence of R-E of the G(L) component on the laser power is attributed to a temperature dependent electron-phonon coupling.
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| 22. |
- Carlsson, Per-Anders, 1972, et al.
(author)
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Bistable mean-field kinetics of CO oxidation on Pt with oxide formation
- 2005
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In: Applied Surface Science. ; 239, s. 424-31
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Journal article (peer-reviewed)abstract
- The bistability of the kinetics of CO oxidation on Pt at sub-atmospheric pressures can be complicated by surface-oxideformation. We present a simple mean-field model making it possible to describe a transition from the low reactive reactionregime occurring via the conventional mechanism of CO oxidation at CO excess, to the high reactive regime including COinteraction with a fully developed surface-oxide overlayer at O2 excess. In the latter case, the oxide is assumed to form islands,the CO2 formation may run primarily on oxide, and in agreement with recent experiments the reaction rate may be several ordersof magnitude lower than the CO adsorption rate on a bare metal surface.
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| 23. |
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| 24. |
- Cho, N. J., et al.
(author)
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Quartz crystal microbalance with dissipation monitoring of supported lipid bilayers on various substrates
- 2010
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In: Nature Protocols. - : Springer Science and Business Media LLC. - 1754-2189 .- 1750-2799. ; 5:6, s. 1096-1106
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Journal article (peer-reviewed)abstract
- Supported lipid bilayers (SLBs) mimic biological membranes and are a versatile platform for a wide range of biophysical research fields including lipid-protein interactions, protein-protein interactions and membrane-based biosensors. the quartz crystal microbalance with dissipation monitoring (QCM-D) has had a pivotal role in understanding SLB formation on various substrates. as shown by its real-time kinetic monitoring of SLB formation, QCM-D can probe the dynamics of biomacromolecular interactions. We present a protocol for constructing zwitterionic SLBs supported on silicon oxide and titanium oxide, and discuss technical issues that need to be considered when working with charged lipid compositions. Furthermore, we explain a recently developed strategy that uses an amphipathic, a-helical (AH) peptide to form SLBs on gold and titanium oxide substrates. the protocols can be completed in less than 3 h.
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| 25. |
- Churchard, A. J., et al.
(author)
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A multifaceted approach to hydrogen storage
- 2011
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 13:38, s. 16955-16972
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Journal article (peer-reviewed)abstract
- The widespread adoption of hydrogen as an energy carrier could bring significant benefits, but only if a number of currently intractable problems can be overcome. Not the least of these is the problem of storage, particularly when aimed at use onboard light-vehicles. The aim of this overview is to look in depth at a number of areas linked by the recently concluded HYDROGEN research network, representing an intentionally multi-faceted selection with the goal of advancing the field on a number of fronts simultaneously. For the general reader we provide a concise outline of the main approaches to storing hydrogen before moving on to detailed reviews of recent research in the solid chemical storage of hydrogen, and so provide an entry point for the interested reader on these diverse topics. The subjects covered include: the mechanisms of Ti catalysis in alanates; the kinetics of the borohydrides and the resulting limitations; novel transition metal catalysts for use with complex hydrides; less common borohydrides; protic-hydridic stores; metal ammines and novel approaches to nano-confined metal hydrides.
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