Use of mixed self-assembled monolayers in a study of the effect of the microenvironment on immobilized glucose oxidase

Mixed self-assembled monolayers (SAMs) composed of a medium length, reactiv e, n-organothiol (11-mercaptoundecanoic acid) and a short length, unreactiv e, hydrophobic n-alkylthiol (7-heptanethiol) chemisorbed onto evaporated go ld surfaces, were used to study the effect of the microenvironment on the s tructure and activity of immobilized glucose oxidase (GOX). The mixed SAMs were characterized by X-ray photoelectron spectroscopy, contact angle measu rements, and cyclic voltammetry. The derivatization of the SAMs for the cov alent attachment and the immobilized enzyme were studied by X-ray photoelec tron spectroscopy. Quantitative analysis of the amide I band of the infrare d spectra of GOX immobilized onto surfaces at the two attainable extremes o f the hyrdrophilicity range available to us indicated that the percentage o f beta sheet increased with increasing hydrophilicity of the microenvironme nt. The specific activity of GOX was higher when the enzyme was immobilized onto the hydrophobic microenvironment.