Hydrophobic collapse induces changes in the collective protein and hydration low frequency modes

Abstract Rapid kinetic terahertz absorption spectroscopy (KITA) was used to directly probe changes in the collective protein–solvent dynamics during protein folding subsequent to a temperature jump. We monitored changes in the low frequency absorption of the solvated protein λ 6 − 85 * with a time resolution of less than 50 μs. Absorption at low frequency yields information about the collective protein–solvent interaction. The spectral changes below 2 THz are correlated with the hydrophobic collapse of λ 6 − 85 * , while there is no indication of any correlation with secondary structure formation, which is an order of magnitude faster.