ENZYME-CATALYZED POLYMERIZATION OF 8-HYDROXYQUINOLINE-5-SULFONATE BY IN-SITU NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

In this report, we describe the use of in situ NMR spectroscopy to elu cidate the mechanism of horseradish peroxidase-catalyzed oxidative fre e-radical coupling of phenols. We demonstrate the potential of the tec hnique for the polymerization of 8-hydroxyquinoline-5-sulfonate (HQS). Based on the structural changes, we establish the involvement of orth o- and para-position protons (to the hydroxyl group) in the oxidative free-radical coupling polymerization with their relative preferences. For example, in HQS, we establish that the positions 2, 4, and 7 are i nvolved in the chemical bonding with the order of preference being 7 g reater than or equal to 2 > 4. Analyses of C-13-NMR data suggest the f ormation of C-C- and C-O-C-type coupling bonds during enzymatic polyme rization. (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1257-1 264, 1998.