Reaction rate enhancement by surface diffusion of adsorbates.
Ligands can be captured by a surface target through either direct bulk diffusion or surface diffusion following reversible adsorption to the surface. We have solved a steady state boundary value problem for a perfect sink disk target in the surface, taking into account bulk and surface diffusion coefficients D and Ds and adsorption/desorption kinetic rate constants ka and kd at non-target regions. Solutions have been successfully found by numerical computation. The results show that the rate of capture from the surface depends non-linearly on Ds, D, ka, kd and geometrical dimensions. In particular, we demonstrate that not only is the non-target region equilibrium constant Keq (= ka/kd) important in determining the rate of capture from the surface, but so are the kinetic rate constants ka and kd separately. In all cases, the surface adsorption/diffusion combination enhances the total rate of capture. The results should be useful for predicting reaction rates of biological membrane bound receptor clusters and substrate-immobilized enzymes.
Wang
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Biophysics Research Division, University of Michigan, Ann Arbor 48109.
Gou
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Axelrod
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D000327:Adsorption; D055598:Chemical Phenomena; D002621:Chemistry; D003201:Computers; D004058:Diffusion; D007700:Kinetics; D008024:Ligands; D008566:Membranes / Q000737:chemistry; D008956:Models, Chemical; D013499:Surface Properties
D008024:Ligands