| Autor: |
Schomacker, K. T., Champion, P. M. |
| Předmět: |
|
| Zdroj: |
Journal of Chemical Physics; 6/1/1989, Vol. 90 Issue 11, p5982, 12p |
| Abstrakt: |
We have measured the resonance Raman cross sections of the predominant modes of ferrocytochrome c as a function of temperature. The data are fit quite successfully with a Kramers–Kronig transform technique and a first-order resonance Raman cross-section expression, which explicitly separates effects due to the thermal properties of the absorption line shape from the Bose–Einstein factor of the Raman mode. The results give experimental support to the assumption that corrections due to higher order scattering processes are negligible for systems that contain many weakly coupled thermally populated modes and verify approximate theoretical expressions for the resonance Raman cross sections at finite temperature. The results also demonstrate that higher order scattering processes cannot account for the recently observed anomalous enhancement of the resonance Rayleigh cross section of ferrocytochrome c. Finally, transient resonance Raman experiments that probe the local temperature of the heme group are suggested and the method of analysis is discussed. These experiments are considered in light of recent molecular dynamics calculations that predict photon absorption will lead to a significant increase in the heme temperature that dissipates within 40 ps. We present expressions, appropriate for absorbing media, that suggest how the mode selective temperature of the heme group can be directly measured by use of the resonant Stokes and anti-Stokes scattering cross sections. Calculations, specific to hot transient states of myoglobin, are presented in order to help quantify the analysis of recent subpicosecond resonance Raman measurements. Recent applications of anharmonic exchange models to obtain heme temperatures are shown to be inappropriate when kT>=hΩb. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
