Transient two-dimensional spectroscopy with linear absorption corrections applied to temperature-jump two-dimensional infrared

Abstract

Multidimensional spectroscopies provide increased spectral information but time resolution is often limited by the picosecond lifetimes of the transitions they probe. At the expense of additional complexity, transient multidimensional techniques extend the accessible timescales for studying nonequilibrium chemical and biophysical phenomena. Transient temperature-jump (T-jump) experiments are particularly versatile, since they can be applied to any temperature-dependent change of state. We have developed a method to correct transient nonlinear techniques for distortions resulting from transient linear absorption of the probing pulses, distortions which can lead to false interpretations of the data. We apply these corrections in the collection of T-jump transient two dimensional infrared spectra for the peptides diglycine and the beta-hairpin peptide trpzip2. For diglycine, the T-jump induces changes in H-bonding, a response which is inherent to all aqueous systems. The trpzip2 results probe the hairpin unfolding kinetics and reveal two time scales: <10 ns increased flexibility and 1:1 mus beta-hairpin disordering.