Two-dimensional infrared spectroscopy of dipeptides in trehalose glass

Abstract

Two-dimensional amide I infrared spectra of three dipeptides in trehalose/D₂O glass were collected via heterodyned three-pulse vibrational echo experiments in order to investigate the distribution of peptide structures and the dynamics of structural evolution in this biologically relevant medium. The hydroxylic solvation environment presented to proteins by trehalose/water glasses has been speculated to be similar to water. The 2D IR spectra are spread along the diagonal, revealing the presence of very broad inhomogeneous distributions, and the lack of spectral dependence on waiting-time shows that these distributions are mainly static with only a small spectral diffusion component consistent with the measurements of the frequency–frequency correlation functions. Polarization-dependent measurements show that the average structure of trialanine in trehalose glass is different from that in water (D₂O).

Keywords:

• Dipeptides
• Trehalose glass
• Two-dimensional infrared spectroscopy

Acknowledgements

This research was supported by grants from NIH P41, GM12592 and NSF with instrumentation from the Research Resource NIH RR01348. CHL gratefully acknowledges the National Institutes of Health for NRSA postdoctoral fellowship 1 F32 GM069274-01. We thank Jane Vanderkooi, Wayne Wright and Bogumil Zelent for advice and use of facilities in sample preparation.