Energy Transduction and Deterministic Protein Motions

Femtosecond optical Kerr effect studies of water

“…The effects of the finite laser pulse duration (hence spectrum) are eliminated by the deconvolution operation of computing the complex quotient where ± refers to the sense of the local oscillator through ±t in eqs 2 and 3, C is the detector constant, $' is the index part of xg>, and all time and frequency dependencies have been suppressed. The in-phase local oscillator probes the imaginary, or loss, part (x$") that is related to the Raman cross section of the sample,10 ^L, -phase = =F 2 [X^7pump/probe]) (6) while the complex local oscillator probes the complex x$.…”

“…Recent reports of the OKE response of water have obtained some of the frequency components.4•5 A similar report has been made in connection with the background contributions of water in the study of the low-frequency modes of proteins. 6 In the current study, the dynamic properties of water have been probed with two different laser sources, providing pulse widths in the range 38-45 fs. These studies have attained sufficient signal to noise ratios (S/N) and time resolution to observe the librational modes near 700 cm'1 down to the diffusive translational and rotational motions around 5 cm'1.…”