AVS 50th International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeM

Paper BI-WeM6
Scaled Interfacial Activity of Proteins at the Liquid-Vapor Interface

Wednesday, November 5, 2003, 10:00 am, Room 317

Session: Bionanoscale Analysis: Theory to Experiment
Presenter: A. Krishnan, The Pennsylvania State University
Authors: A. Krishnan, The Pennsylvania State University
J. Sturgeon, The Pennsylvania State University
C.A. Siedlecki, The Pennsylvania State University
E.A. Vogler, The Pennsylvania State University
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A principal conclusion drawn from observations of time- and concentration-dependent liquid-vapor (LV) interfacial tension @gamma@@sub lv@ of a diverse selection of proteins ranging from albumin to ubiquitin is that concentration scaling substantially alters perception of protein interfacial activity, as measured by the amount adsorbed to the hydrophobic LV surface. Proteins appear more similar than dissimilar on a weight/volume basis whereas molarity scaling reveals a "Traube-rule" ordering by molecular weight, suggesting that adsorption is substantially driven by solution concentration rather than diversity in protein amphilicity. Scaling as a ratio-to-physiological-concentration demonstrates that certain proteins exhibit the full possible range of interfacial activity at-and-well-below physiological concentration whereas others are only weakly surface active within this range, requiring substantially higher solution concentration to achieve maximum adsorption to the LV interface. Important among this latter category of proteins are the blood factors XII and XIIa, assumed by the classical biochemical mechanism of plasma coagulation to be highly surface active, even in the presence of overwhelming concentrations of other blood constituents such as albumin and immunoglobulin that are shown by this work to be among the class of highly-surface-active proteins, at physiologic concentration. A comparison of pendant-drop and Wilhelmy-balance tensiometry as tools for assessing protein interfacial activity shows that measurement conditions employed in the typical Wilhelmy plate approach fails to achieve the steady-state adsorption state that is accessible to pendant-drop tensiometry. A comparison of bovine and human proteins reveals substantial differences in adsorption to the LV interface, apparently arising from as-yet unresolved speciation effects.