PROTEIN DYNAMICS FROM TIME-RESOLVED
RAMAN SPECTROSCOPY: HEMOGLOBIN

Thomas G. Spiro, Ph.D.
Chemistry Department
Princeton University

Seminar Host: UCSF Molecular Design Institute  

2:00
May 22, 1998
S 214

Abstract

Structural dynamics in proteins can now be monitored in real time using time-resolved vibrational spectroscopy. Pulse-probe Raman spectroscopy can focus on specific structural elements through the selectivity conferred by the resonance Raman effect. Tyrosine and tryptophan residues are particularly useful probes of protein dynamics, and can be accessed by UV Raman excitation. Step-scan FTIR is a useful complement to Raman monitoring. Although selective excitation is unavailable, the FTIR spectrum can be subtracted very accurately, leaving characteristic difference signals at single-residue sensitivity. 

These techniques have been applied to hemoglobin, which serves as a paradigm for understanding allostery. With the aid of isotope-labelling, chemical modification and mutation, the spectroscopic data have produced a model of the allosteric reaction coordinate, involving reciprocating helix and subunit motions, leading to inter-dimer rotation and strain generation at the heme in the T state.

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