Membrane Phenomenon and Surface Dilution Kinetics

One of the major difficulties in studying enzymes acting in and on membranes and receptors localized therein is that biological phenomenon occur in two dimensional space rather than in the three dimensional solutions that have been traditionally studied by biochemists. In the early 1970’s, we developed a novel approach to such studies called “surface dilution” kinetics [Review: 175] which provides an overall framework for examining the action of a variety of signal transduction enzymes on surfaces. In this system the substrate concentration is expressed in surface dilution units of mole fraction and allows analysis of kinetics. We have also studied these enzymes structurally by x-ray (202) and NMR (171) where we have also examined the interaction with interfaces such as micelles. We are now applying the surface dilution phenomenon to the analysis of activators (220) and inhibitors which in general partition with the surface and must be considered in surface dilution units. This analysis is central to analyzing the activation and inhibition of signal transduction enzymes with multiple binding sites.