Surface-protein interaction

Protein adsorption has been studied with a variety of techniques such as ellipsome-try [107,108], ESCA [109], surface forces measurements [102], total internal reflection fluorescence (TIRE) [103,110], electron microscopy [111], and electrokinetic measurement of latex particles [112,113] and capillaries [114], The TIRE technique has recently been adapted to observe surface diffusion [106] and orientation [IIS] in adsorbed layers. These experiments point toward the significant influence of the protein-surface interaction on the adsorption characteristics [105,108,110]. A very important interaction is due to the hydrophobic interaction between parts of the protein and polymeric surfaces [18], although often electrostatic interactions are also influential [ 116]. Protein desorption can be affected by altering the pH [117] or by the introduction of a complexing agent [118]. 

Separations in hydrophobic interaction chromatography have been modeled as a function of the ionic strength of the buffer and of the hydrophobicity of the column, and tested using the elution of lysozyme and ovalbumin from octyl-, butyl- and phenyl-Sepharose phases.2 The theoretical framework used preferential interaction analysis, a theory competitive to solvophobic theory. Solvophobic theory views protein-surface interaction as a two-step process. In this model, the protein appears in a cavity in the water formed above the adsorption site and then adsorbs to the phase, with the free energy change... 

We need to have drugs, antidotes, and cures for the weapons of mass destruction that terrorists are likely to use. To develop medicinal countermeasures, the basic science involved must first be understood. For both chemical and biological weapons, the process of molecular recognition by elements of the human body is of utmost importance. However, we do not have a clear understanding of protein surface interactions, the relationship of genes to protein function, and how viruses infect and replicate. All of these processes are chemical in nature and caimot be solved without knowledge of the chemical sciences. 

At about the same time, the field of protein separation and purification was undergoing rapid development. The introduction of materials for protein chromatography, such as cross-linked dextran, agarose, and polyacrylamide, provided a means to study protein-surface interactions, as well as to dramatically advance knowledge in protein biochemistry. 

It is recommended that any reader seriously interested in protein adsorption obtain Teaching Aids for Macromolecular Structures 28), which is commercially available for about 20.00. These aids clearly show the dramatic potential of surface protein structural visualization for the development of hypotheses of protein-surface interactions. 

Apparently, no single factor can be used to predict the process of adsorption there are always several different properties of protein and adsorbent that determine the protein-surface interaction. As a summary, the following general guidelines can be given ... 

Surface-induced change in conformation which optimizes protein-surface interaction and decreases the probability for desorption ... 

Studies of the role of protein-surface interactions in blood coagulation were done by Vroman 56). The plasma proteins were adsorbed onto various hydrophilic or hydrophobic surfaces. Vroman showed that fibrinogen was an important component of the plasma protein layer adsorbed to the solid/liquid interface. 

Protein surface structure and conformational dynamics are now much better understood. In the near future, we can expect extensive application of computer molecular graphics to better visualize and understand protein-surface interactions. 

The use of these natural fluorescence techniques offers not only the possibility of studying the interaction of proteins with membranes, under convective and diffusive conditions, but also they may be easily extended to studies involving proteins and other porous materials such as chromatography media. The areas of application of these techniques will range from polypeptide and protein fractionation to the monitoring of systems where protein-surface interactions are relevant. 

Jeon SI, Lee JH, Andrade JD et al (1991) Protein surface interactions in the presence of polyethylene oxide). 1. Simplified theory. J Colloids Interf Sci 142 149-158... 

Fig. 8. Schematic representation of protein-mediated cell adhesion on biomaterial surfaces. Biomaterial surface properties (such as hydrophilicity/hydrophobicity, topography, energy, and charge) affect subsequent interactions of adsorbed proteins these interactions include but are not limited to adsorbed protein type, concentration, and conformation. Changes in protein-surface interactions may alter accessibility of adhesive domains (such as the peptide sequence arginine-glycine-aspartic acid) to cells (such as osteoblasts, fibroblasts, or endothelial cells) and thus modulate cellular adhesion. (Adapted and redrawn from Schakenraad, 1996.)...

C. Multiparticle Interactions, Deformable Interfaces, and Protein-Surface Interactions... 

Huang H, Melacini G. High-resolution protein hydration NMR experiments probing how protein surfaces interact with water and other non-covalent ligands. Analyt. Chim. Acta 2006 564 1-9. 

While these conclusions are directed towards the fibrinogen-albumin mixture study, this type of FTIR analysis of proteins has general applicability. These results indicate that FTIR can produce usable spectra of flowing aqueous protein solutions, and these spectra can in turn provide useful molecular-level information concerning protein-surface interactions. 

Both the nature of protein-surface interactions and inherent properties of a specific enzyme will contribute to the catalytic activity of an immobilized biocatalyst. Adsorption of an enzyme onto a surface can induce conformational changes which affect the rate and specificity of the catalyst. The total amount of enzyme loading, enzyme distribution within the immobilization support, and microenvironment surroimding the supported enzyme can all influence enzyme-catalyst activity, specificity and stability. ... 

In the following description of early studies as well as of our recent findings, I will use the classification of protein/surface interactions given above. Among the proteins to be discussed fibrinogen will be prominent, not only because of our own work, but also because this work fits rather well within the context of others studies showing protein, plasma and cellular (platelet) interactions. 

At present, the protein/surface interactions that determine adsorption kinetics are unclear. To clarify these interactions, the effects of polymer surface properties on protein adsorption and desorption rates have been investigated. BSA adsorption from a 1 mg% solution (1 mg% = 1 mg/100 mL) was studied using several polymers chosen for their wide range of surface properties and functionalities (22, Cheng, Y.L. et al.. J. Coll. Int. Sci., in press). The polymers and their surface properties (under the conditions of the BSA adsorption experiments) are listed in Table I. 

The main purpose of our present studies is to investigate the details of protein-surface interactions with relevance to questions regarding biocompatibility, fouling and the possible development of (implantable) biosensors. 

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