Helium droplet infrared spectroscopy of glycine and glycine–water aggregates

Abstract

Infrared absorption spectra of glycine and glycine–water aggregates embedded in superfluid helium nanodroplets were recorded in the frequency range 1000–1450 cm⁻¹. For glycine monomer, absorption bands were observed at 1106 cm⁻¹, 1134 cm⁻¹, and 1389 cm⁻¹. These bands were assigned to the C–OH stretch mode of the glycine conformers I, III and II, respectively. For glycine–water aggregates, we observed two bands at 1209 cm⁻¹ and 1410 cm⁻¹ which we assign to distinct conformers of glycine–H₂O. In all cases, the water is found to preferentially bind to the carboxyl group of the glycine.