Quantitation of the Escherichia coli methionine repressor-operator interaction by surface plasmon resonance is not affected by the presence of a dextran matrix

The effect of a dextran matrix on the apparent rate constants measured for the interaction of the Escherichia coli methionine repressor, MetJ, with its immobilized consensus operator has been studied using surface plasmon resonance (SPR) in a commercial biosensor, BLACORE (Biacore AB), Based on the results of computer simulations, it has been proposed that such data can deviate from the expected simple kinetic behavior due to effects generated by the dextran matrix, used at the biosensor surface to anchor one of the interacting molecules. We have tested this possibility experimentally by measuring the apparent rate constants for the interaction of MetJ with its operator DNA on sensor chip surfaces with no dextran matrix or having matrices 30 or 100 nm thick. The data show that for the MetJ-operator interaction, the dextran matrix has no significant effect on the apparent rate constants measured and that comparative measurements using this technique are informative. (C) 1997 Academic Press.