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| 2. |
- Feiler, Adam, et al.
(författare)
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Effect of capillary condensation on friction force and adhesion
- 2007
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:2, s. 517-522
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Tidskriftsartikel (refereegranskat)abstract
- Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobised) after long (24 hour) exposure to high humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction-load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate with the hydrophobised silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.
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| 3. |
- Feiler, Adam, et al.
(författare)
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Effect of relative humidity on adhesion and frictional properties of micro- and nano-scopic contacts
- 2005
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Ingår i: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 19:05-mar, s. 165-179
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Tidskriftsartikel (refereegranskat)abstract
- The effect of relative humidity (RH) oil the interactions of AFM tips and colloidal probes with hydrophilic silica substrates is investigated. Both friction and adhesion are studied. For the case of a colloidal probe the interaction is characteristic of a multiasperity contact, the adhesion increased with increasing RH and above a certain threshold relative humidity a large increase in adhesion was measured. This behaviour is explained in terms of a recent model where the Kelvin radius of the condensate becomes larger than some characteristic roughness on the surface. The interaction between the tip and the substrate also exhibited an increase in adhesion above a threshold RH although the increase was much less marked than with the colloid probe. The friction decreased with increasing humidity for both tip and colloid probe although the friction force was much less sensitive than adhesion to changes in RH. Stick-slip behaviour was observed between tip and substrate for all humidities at high loads, but only at the lowest RH (about 5%) it was observed at all loads. At higher humidity the behaviour became increasingly continuum on the experimental timescale, presumably due to viscous contributions from the water. Stick-slip was not observed for the colloidal probe friction measurements.
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| 4. |
- Jenkins, HT, et al.
(författare)
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Human C4b-binding protein, structural basis for interaction with streptococcal M protein, a major bacterial virulence factor
- 2006
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 281:6, s. 3690-3697
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Tidskriftsartikel (refereegranskat)abstract
- Human C4b-binding protein (C4BP) protects host tissue, and those pathogens able to hijack this plasma glycoprotein, from complement-mediated destruction. We now show that the first two complement control protein (CCP) modules of the C4BP alpha-chain, plus the four residues connecting them, are necessary and sufficient for binding a bacterial virulence factor, the Streptococcus pyogenes M4 (Arp4) protein. Structure determination by NMR reveals two tightly coupled CCP modules in an elongated arrangement within this region of C4BP. Chemical shift perturbation studies demonstrate that the N-terminal, hypervariable region of M4 binds to a site including strand 1 of CCP module 2. This interaction is accompanied by an intermodular reorientation within C4BP. We thus provide a detailed picture of an interaction whereby a pathogen evades complement.
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