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- Bergkvist, Magnus, et al.
(författare)
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A method for studying protein orientation with atomic force microscopy using relative protein volumes
- 2001
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 105:10, s. 2062-2069
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Tidskriftsartikel (refereegranskat)abstract
- A method for studying protein orientation is described, in which the relative volumes of single proteins and single molecule complexes are measured using atomic force microscopy (AFM). Site-specific ligands are used as “probes” to bind to surface adsorbed proteins. The quantity of formed complexes gives an estimate of the amount of protein oriented in such a way as to allow ligand binding. The volume distribution for single proteins adsorbed to a surface was calculated and fitted to a Gaussian function. This volume distribution was used to localize the same proteins on surfaces with protein−ligand complexes, thus rendering it possible to find the amount of complex formed. Two model systems were used: one with two different mouse monoclonal antibodies of IgG1 type (mAb's against human serum transferrin, hST) adsorbed on silicon surfaces, and one with hST adsorbed to unmodified mica and aminated mica. The adsorbed proteins were allowed to react with a site-specific ligand, which binds to a defined region of the adsorbed protein (hST in the case of adsorbed mAb and lectin in the case of adsorbed hST). A great difference in ligand binding was found between the two antibodies adsorbed to the same type of surface as well as between hST adsorbed to different surfaces. This differance can be attributed to different orientation of the proteins on the surface. The general approach of this method suggests that it can be used for almost any site-specific molecule, either for surface orientation studies or studies where single molecule interactions need to be investigated.
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| 4. |
- Bergkvist, Magnus, et al.
(författare)
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Surface-dependent conformations of human plasma fibronectin adsorbed to silica, mica, and hydrophobic surfaces, studied with use of Atomic Force Microscopy
- 2003
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Ingår i: Journal of biomedical materials research. Part A.. - : Wiley. - 0021-9304 .- 1097-4636. ; 64:2, s. 349-356
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Tidskriftsartikel (refereegranskat)abstract
- Human plasma fibronectin (Fn) is a large flexible protein stabilized by intermolecular ionic interactions forming a compact structure. On altering solution conditions, the structure can revert to a more expanded state, thereby exposing previously hidden domains (e.g., cell-binding sites). Electron microscopy images of Fn air-sprayed onto mica surfaces show elongated protein structures, indicating a surface-induced structural change. This makes it interesting to investigate the influence of surface properties on the structure of adsorbed Fn. We have used intermittent-contact Atomic Force Microscopy to investigate the structure of Fn adsorbed onto mica, silica, and methylated silica surfaces. We observed that on silica surfaces, which is hydrophilic, most (70%) of the molecules had an elongated structure with partial intramolecular chain interactions, compare to molecules adsorbed on hydrophobic, methylated surfaces, where a compact structure predominated (70%). On mica surfaces, both compact and elongated protein structures were observed, with a slight preference for the elongated form (53%). Results show that surface physical properties influence the molecular structure of fibronectin on adsorption, which could provide useful information in understanding surface-induced in vivo responses.
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| 5. |
- Bergkvist, Magnus, et al.
(författare)
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TM-AFM Threshold Analysis of Macromolecular Orientation : A Study of the Orientation of IgG and IgE on Mica Surfaces
- 1998
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 206:2, s. 475-481
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption and orientation properties of two different types of immunoglobulin molecules on derivatized and native mica surfaces were investigated using TM-AFM. The analyses included height measurements at two different pH values and a new technique, presented here as threshold analysis, which displays the outer mantle shape of an adsorbed protein. A major difference in preferential orientation is observed upon comparing the adsorption of the two proteins onto the different surfaces. The characteristics of both the adsorbed immunoglobulin and the surface are important for any preferential orientation of the adsorbed protein.
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| 6. |
- Bergstedt Oscarsson, Kristina, et al.
(författare)
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Human Puumala hantavirus infection in northern Sweden : increased seroprevalence and association to risk and health factors
- 2016
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Ingår i: BMC Infectious Diseases. - : Springer Science and Business Media LLC. - 1471-2334. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The rodent borne Puumala hantavirus (PUUV) causes haemorrhagic fever with renal syndrome in central and northern Europe. The number of cases has increased and northern Sweden has experienced large outbreaks in 1998 and 2006-2007 which raised questions regarding the level of immunity in the human population.METHODS: A randomly selected population aged between 25 and 74 years from northern Sweden were invited during 2009 to participate in a WHO project for monitoring of trends and determinants in cardiovascular disease. Health and risk factors were evaluated and sera from 1,600 participants were available for analysis for specific PUUV IgG antibodies using a recombinant PUUV nucleocapsid protein ELISA.RESULTS: The overall seroprevalence in the investigated population was 13.4 %, which is a 50 % increase compared to a similar study only two decades previously. The prevalence of PUUV IgG increased with age, and among 65-75 years it was 22 %. More men (15.3 %) than women (11.4 %) were seropositive (p < 0.05). The identified risk factors were smoking (OR = 1.67), living in rural areas (OR = 1.92), and owning farmland or forest (OR = 2.44). No associations were found between previous PUUV exposure and chronic lung disease, diabetes, hypertension, renal dysfunction, stroke or myocardial infarction.CONCLUSIONS: PUUV is a common infection in northern Sweden and there is a high life time risk to acquire PUUV infection in endemic areas. Certain risk factors as living in rural areas and smoking were identified. Groups with increased risk should be targeted for future vaccination when available, and should also be informed about appropriate protection from rodent secreta.
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| 7. |
- Deirmina, Faraz, et al.
(författare)
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Influence of boron on the stress-rupture behavior of an additively manufactured Hastelloy X
- 2023
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 863
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Tidskriftsartikel (refereegranskat)abstract
- The influence of minor additions of boron and the as-built (AB) microstructure on stress-rupture behavior of a modified crack-free Hastelloy X fabricated by laser powder bed fusion (L-PBF) was investigated. Isothermal stress rupture tests were performed at 816 degrees C under a static tensile load of 103 MPa. Micro-void formation in the vicinity of carbide precipitates and their coalescence was only observed at chevron-like high-angle grain boundaries, characteristic of L-PBF process. These grain boundaries, laying on the planes with maximum resolved shear stress with respect to the loading direction, directly governed the intergranular crack propagation. In view of the fracture mechanism and the time to rupture, increasing boron content significantly improves timeto-rupture through a diffusion-controlled mechanism by hindering the carbon diffusion to the grain boundaries. Adequate additions of boron (>10 ppm) guarantee the stress-rupture properties (strength) of the AB components without the need for additional post-thermal treatments. Further increase in boron content (i.e., 30 ppm), led to about five times increase in time to rupture (500 h vs. 110 h), and significantly improved creep elongation (30% vs. 9%) compared with the low boron alloy.
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