"Efficient catalytic cascades that involve several sequential reactions are found frequently in nature. The efficiency of multi-step biochemical pathways is enhanced by substrate channeling, wherein the product of one reaction is directed toward and acts a substrate to the next sequential reaction. This mechanism can partially overcome diffusion, which is often fast compared to reaction rates, and promotes loss of intermediates. Substrate channeling is achieved by the architecture and scaffolding of biological molecules, and mimicking these natural structures could lead to innovative catalyst designs. We investigate the efficiency of two channeling approaches - electrostatic interactions and surface adsorption - through continuum modeling, to identify the limits of these modes and the extent to which they can interact. The model considers transport between two active sites where an intermediate is produced at the first active site and consumed at the second. The system includes mass transport through diffusion and migration, and reaction kinetics at the active sites. The effectiveness of this model is quantified by yield of the second reaction and by flux control coefficients (FCCs). Controlling the proximity between active sites, and surface adsorption are found to be inefficient as high rate constants are required to obtain significant yields. The introduction of electrostatic interactions, however, leads to yields of over 90% at low rate constants."--Pages ii.
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