Synthesis, Postmodification and Characterization of Linear Polystyrene-based Supports for the Interaction with Immobilized Biocatalysts

A series of linear polystyrene-based supports has been synthesized using conventional or controlled (reversible addition fragmentation chain transfer or nitroxide-mediated) free radical polymerizations, in order to modulate their molecular weight characteristics. Polymer post-modification via esterification of the primary hydroxyl alcohol functionalities, pendant from the polymer backbone, with a mandelic acid derivative introduces efficiently (>85% yield) racemic, enzyme-cleavable moieties. A study of the interactions of these polymeric substrates with immobilized penicillin G acylase, in mixed organic/aqueous buffer solvent systems, results in a modest enantioselectivity (comparable with that of racemicmandelic acid methyl ester), but reveals that the biocatalytically active moieties on the linear polymers can be cleaved with first-order rate kinetics, as observed with small molecules in solution; the reaction rates (which can differ by more than one order ofmagnitude) are influenced both by the synthetic polymer length and by the polymer structure resulting from themethod of polymerization used.