Optical characterization of glutamate dehydrogenase monolayers chemisorbed on SiO2

This paper describes the formation of glutamate dehydrogenase monolayers on silicon dioxide, and their characterization by phys. techniques, i.e., fluorescence spectroscopy and Fourier-transform IR spectroscopy. Detailed investigations of the intrinsic stability of native proteins in soln. were carried out to elucidate the occurrence of conformational changes induced by the immobilization procedure. The enzyme monolayers were deposited on SiO2 after pre-exposing silicon surfaces to 3-aminopropyltriethoxysilane and reacting the silylated surfaces with glutaric dialdehyde. The optical characterization demonstrates that the immobilization does not interfere with the fold pattern of the native enzyme. In addn., fluorescence spectroscopy, thermal denaturation, and quenching studies performed on the enzyme in soln. well describe the folding and unfolding properties of glutamate dehydrogenase. The photophys. studies reported here are relevant for nanobioelectronics applications requiring protein immobilization on a chip.