Film techniques for vibrational circular dichroism measurements

Abstract

Vibrational circular dichroism (VCD) spectra in the 1800-900 cm(-1) region have been measured recently for protein films and for carbohydrate films prepared from aqueous solutions. In addition to the advantages of avoiding the interference from strong infrared absorption of water at 1650 cm(-1) and requiring a two-orders-of-magnitude-smaller amount of sample for film measurements (than those required for the same in water solutions), the VCD bands in film measurements are found to be the same as those in solution measurements and to be independent of film orientation. This latter observation indicated the possibility for routine VCD measurements in the film state. In this manuscript we report different film techniques for VCD measurements. These techniques include preparation of supported films, free-standing films, film-on-film, and facilitation of film formation for substances that otherwise do not form amorphous films. The experimental data for films prepared by each of these techniques are presented and the relative merits of these different methods are discussed.