Fibrinogen surface denaturation

The size of a molecule is an important feature because proteins form multiple contacts with the surface (e.g., 77 contact points in the case of the albumin molecule and 703 contact points in the case of the fibrinogen molecule adsorbed on silica [10]). Multipoint binding usually causes adsorption irreversibility having a dynamic nature in the absence of irreversible denaturation. The rates of desorption are, as a rule, much lower than those of adsorption, and in many cases it is virtually impossible to attain the equilibrium state desorbing the adsorbed protein [11]. In other words, the formation of one or several bonds with the surface increases the probability of adsorption of neighboring sites of the same molecule. On the other hand, the desorption of a protein molecule requires the simultaneous rupture of a large number of bonds and, for kinetic reasons, equilibrium is not attained [12-14], This corresponds to a considerable difference between the activation energies for the adsorption and desorption processes [15,16],... 

Since we have shown previously that at very long periods (days) significant portions of almost completely denatured albumins, y-globulin, and fibrinogen are desorbed from hydrophobic surfaces, this effect also is probably related to entropic considerations. 

Our main contributions to the study of denaturation consist of experiments to evaluate the structural status of fibrinogen eluted from glass. Clearly, it would be preferable to evaluate structural alteration while the protein remains on the surface but such an approach presents formidable experimental difficulties, not the least of which is sensitivity. Therefore, we made the compromise of studying eluted protein and making the tacit assumption that the eluted protein is structurally similar to the adsorbed protein. The eluents used (high molarity buffers and surfactants) were shown not to affect the properties examined. 

Skarja, G. A., Brash, J. L., Bishop, R, and Woodhouse, K. A. (1998). Protein and platelet interactions with thermally denatured fibrinogen and crosslinked fibrin coated surfaces, BigmgiSJTols, 19,2129-2138. 

So far, no general principles aUow the full prediction of the effect of surface chemistry on protein and cell behavior. However, some guidelines could be drawn from extensive research. Methyl (-CH3), nonpolar, hydrophobic groups allow strong binding of fibrinogen and IgG, which causes alterations in the conformations and denaturation of the protein structures, possibly leading to unfavorable... 

The question remains whether the denatured protein molecule regains its native structure on desorption. Soderquist and Walton extensively studied the structure of three plasma proteins—albumin, y-globulin and fibrinogen—on desorption from different co-polypeptide (amino acid copolymers) and silicone surfaces under different pH and ionic strength conditions [88]. Circular dichroism (CD) analysis of the surface desorbed proteins showed a marked decrease in the a-helical content for albiunin and fibrinogen, whereas y-globulin lost most of its P-sheet structure. The reduction... 

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