Surface-bound protein

Stuart and Hlady [37] found that unintentional lateral forces influenced their measurements of adhesion between surface-bound protein molecules and colloid probe-bound ligands. They noted a greatly exaggerated separation distance and a stick-shp behavior in their adhesion curves, which they attribute to roUiug and buckling of the cantilever under the influence of lateral forces as the sample was retracted with the probe stuck to it. 

To discriminate between surface bound protein molecules and those in bulk solution, total internal reflection fluorescence microscopy (TIRFM)41 55 was employed. TIRFM creates an evanescence wave that decays as a function of distance from the surface as ... 

Electrode surfaces modified with a multilayered surface architecture prepared by a layer-by-layer repeated deposition of several enzyme mono-layers show a modulated increase of surface-bound protein with a subsequent increase in output current, which is directly correlated with the number of deposited protein layers. The versatility of this approach allows alternate layers of different proteins for the manufacture of electrode surfaces, which are the basis for multianalyte sensing devices with multiple substrate specificities. The surface chemistry used for the manufacture of multilayered electrode surfaces is similar to that previously described for the preparation of affinity sensors, and is based on the stabilization of self-assembled multilayer assemblies by specific affinity interactions, electrostatic attraction, or covalent binding between adjacent monolayers. 

The work discussed here has shown that suspensions of platelets and red cells in a physiological medium can provide information for platelet surface interactions. Evidence is provided on the dynamic features of platelet-surface adhesion and detachment which indicates that more than one sequence of adhesion, detachment and re-adhesion can lead to the same net platelet adhesion. Surface generated substances, such as A DP and serotonin from platelets and thrombin from the coagulation pathway, may strongly influence the function of platelets approaching a surface. The supply of these substances depends on the presence of flow and continued arrival of platelets at a surface. The reactivity of surface-bound protein may be altered by platelet adhesion and detachment. This may occur as a result of deposition of cell membrane components, replacement of the original substrate with protein secreted from platelets or possibly by enzymatic digestion of surface bound protein. 

The alteration of surface-bound protein through adherence and detachment of platelets is but one way that a cell can alter a protein substrate. A number of cells which have been cultured on preadsorbed protein have been shown to alter this protein as well as protein provided by the cell to the surface (31.32). Endocytosis and enzymatic digestion of surface-bound protein are possible mechanisms directly related to functions of adherent cells. Evidence exists to indicate that such processes may be occurring v hen platelets adhere to preadsorbed protein (33). 

Affinity-based proteomics. In affinity-based proteomics, a compound of interest is immobilized to the solid surface by means of functional groups (e.g., NHj) or using the biotin-streptavidin interaction. Cell lysate that contains the target proteins is then incubated with the immobilized compound and this leads to enrichment of proteins on the matrix (1). Stringent washing removes proteins that unspecifically bind to the solid surface. Bound proteins are then released from the matrix by elution (e.g., with an excess of unmodified compound) or by heating... 

Matsuno et al. [5] studied the interactions of y-crystaUins with silica, methylated silica, and diphenyl silica. They used different techniques to examine the secondary and tertiary structural alterations that took place upon adsorption on these sdica surfaces exhibiting different degrees of hydrophobicity. A comparison was made between conformations of free and surface-bound protein as a function of the electrostatic and hydrophobic character of both the protein and the adsorbent surface. They demonstrated that (1) protein destabdization on hydrophobic surfaces is greater than that on more hydrophilic surfaces, (2) detectable conformational changes tend to increase as the surface hydrophobicity increases, and (3) subtle structural differences among proteins can play an important role in determining differences in protein stability and structure upon adsorption. 

T. Weidner and D. G. Castner, SFG Analysis of Surface Bound Proteins A Route towards Structure Determination, Phys. Chem. Chem. Phys., 2013, 15, 12516. 

While pure collagen provided a dry layer thickness of about 80 run, significantly thinner layers in the range between 14 and 32 nm (for fixed, pre-set refractive index values) were measured if heparin or hyaluronic acid were added to fibril-forming solutions (Table 3). The quantification of surface-bound proteins confirmed the results of the elUpsometric measurements noticeable lower collagen amoimts were quantified if fibril formation and immobilization was performed in the presence of glycosaminoglycans. The quantification was supported by surface topographic analysis of the attached fibrillar components (Fig. 7). 

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