AVS 51st International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoA

Paper BI-MoA4
Mixology of Protein Solutions and the Vroman Effect

Monday, November 15, 2004, 3:00 pm, Room 210D

Session: Protein-Surface Interactions
Presenter: A. Krishnan, Pennsylvania State University
Authors: A. Krishnan, Pennsylvania State University
C.A. Siedlecki, Pennsylvania State University
E.A. Vogler, Pennsylvania State University
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Mixing rules stipulating both concentration and distribution of proteins adsorbed to the liquid-vapor(LV) interphase from multi-component aqueous solutions are derived from a relatively straightforward protein-adsorption model. Accordingly, proteins compete for space within an interphase separating bulk-vapor and bulk-solution phases on a weight, not molar, concentration basis. This results in an equilibrium weight-fraction distribution within the interphase that is identical to bulk solution. However, the absolute interphase concentration of any particular protein adsorbing from an m-component solution is 1/mth that adsorbed from a pure, single-component solution of that protein.Applied to adsorption from complex biological fluids such as blood plasma and serum, mixing rules suggest that there is no energetic reason to expect selective adsorption of any particular protein from the mixture. Thus, dilute members of the plasma proteome are overwhelmed at the hydrophobic LV surface by the thirty classical plasma proteins occupying the first-five decades of physiological concentration. Mixing rules rationalize the experimental observations that(i)concentration-dependent liquid-vapor interfacial tension of blood plasma and serum cannot be confidently resolved,even though serum is substantially depleted of coagulable proteins(e.g. fibrinogen) and(ii) of plasma is startlingly similar to that of purified protein constituents. Adsorption-kinetics studies of human albumin (66.3 kDa) and IgM (1000 kDa) binary mixtures revealed that relatively sluggish IgM molecules displace faster-moving albumin molecules adsorbing to the LV surface. This Vroman-effect-like process leads to an equilibrium reflecting the linear combination of w/v concentrations at the surface predicted by theory. Thus, the Vroman effect is interpreted as a natural outcome of protein reorganization to achieve an equilibrium interphase composition dictated by a firm set of mixing rules.