AVS 45th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoM

Paper BI-MoM6
Interfacial Influences on the Apparent Activity of Immobilized Electron Transfer Proteins

Monday, November 2, 1998, 10:00 am, Room 326

Session: Protein Solid-Surface Interactions
Presenter: D.E. Leckband, University of Illinois, Urbana-Champaign
Authors: D.E. Leckband, University of Illinois, Urbana-Champaign
C. Yeung, University of Illinois, Urbana-Champaign
N. Lavrik, University of Illinois, Urbana-Champaign
A. Kloss, University of Illinois, Urbana-Champaign
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We determined the influence of the interfacial microenvironment on the apparent activity of immobilized proteins. In particular, we investigated the effect of the electrostatic potential of the underlying support on the interaction of soluble cytochrome b5 with immobilized cytochrome c. By varying solution pH, we controlled the magnitude of the negative charge on the supporting matrix. Because cyt b5 is also negatively charged at neutral pH, the substrate repels the soluble cyt b5 and thus opposes the cyt c/cyt b5 attraction. We show, using surface plasmon resonance, that the apparent pH-dependence of the interprotein affinity is determined largely by the pH-dependence of the substrate, and not by the intrinsic interactions between the two proteins. On the matrix used in this work, we showed that the pH-optimum for the cyt c/cyt b5 recognition shifts by 1.2 pH units relative to that of the soluble proteins. Our results demonstrate that the apparent biological activity of immobilized species must be considered within the context of the microenvironment in which they function.