Chemically Modified Surfaces Affect the Activation Volume of Adsorbed Enzymes

Abstract

An efficient tool for many biomedical and biotechnological processes is the immobilization of enzymes at aqueous-solid interfaces. Moreover, there are several examples in the literature showing free enzymes which can be activated by pressure. Recently our group reported a pressure-activation of α-chymotrypsin adsorbed on silica particles1. Therefore pressure could compensate an enzymatic activity loss due to adsorption at aqueous-solid interfaces. In the present work, the effect of interfacial chemistry on the activation volumes of adsorbed enzymes is investigated. The measurements were conducted using high-pressure total internal reflection fluorescence (TIRF) spectroscopy up to 2000 bar. The application of TIRF is very convenient to suppress any signal coming from the solution, and it is suitable to analyze chemically modified surfaces prepared by spin-coating or layer-by-layer polyelectrolyte deposition. The activation volumes of two enzymes, α-chymotrypsin (α-CT) and horseradish peroxidase (HRP), adsorbed on bare quartz and on chemically modified quartz, were calculated. The quartz surfaces were modified with thin films of poly(styrene), poly(styrene sulfonate) or poly(allylamine hydrochloride) to create hydrophilic, hydrophobic, positively and negatively charged surfaces. Remarkably, the activation volumes of the adsorbed enzymes show a strong dependence on the type of interfacial chemistry. The results reveal an important role of the chemical nature of an interface on how the enzymes will react with pressure. As a matter of fact, the pressurization of a chemically modified interface might result in a very useful tool to optimize enzymatic processes.[1]V. Schuabb, C. Czeslik, Langmuir 30, 15496 (2014). claus.czeslik@uni-dortmund.deKeywords: enzyme, interface, pressure, activation volume