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Hemoglobin dynamics from transient raman spectroscopy
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JSINETICS 215
coo4
HEMOGLOBIN DYNAMICS FROM TRANSIENT RAMAN SPECTROSCOPY K. R. Rodgers, I. Mukerji, V. Jayaraman, T. G. S&Q
Department of Chemistry, Princeton University, Princeton, NJ
08544
The advent of reliable pulsed lasers whose frequency can be shifted into the ultraviolet region has made possible the application of ultraviolet resonance Raman (UVRR) spectroscopy to biological molecules. For proteins, appropriate tuning of the laser yields selective enhancement of vibrational modes of the aromatic side chains phenylalanine, tyrosine, and tryptophan, or of the amide bonds. The spectra can provide information, at high sensitivity, about protein secondary structure, and about the local environment of aromatic residues. The experiment can also be applied in a time-resolved mode to monitor structural changes associated with transient processes. The R-T quaternary transition in hemoglobin is currently being studied in this manner, using one nanosecond laser to photolyze the CO adduct, and another to generate UVRR spectra. Changes in the tyrosine and tryptophan UVRR signals which develop 20 us after photolysis are attributed to the altered subunit contacts at the a& interface during the R-T rearrangement. A preceding alteration of the tryptophan signal is associated with interior tryptophan residues whose H-bonding is sensitive to helix-helix motions within the subunits. Thus the aromatic residue signals provide indicators of protein motions associated with both tertiary and quaternary rearrangements on the R-T pathway. Mutant and hybrid hemoglobins are providing fresh insights into these protein motions. 1. 2.
K. R. Rodgers, C. Su, S. Subramaniam, and T. G. Spiro, J. Am. Chem. Sot., 1992, 174, 3697. V. Jayaraman, K. R. Rodgers, I. Mukerji, and T. G. Spiro, Biochemistry, 1993 (in press).
JSINETICS 215
coo4
HEMOGLOBIN DYNAMICS FROM TRANSIENT RAMAN SPECTROSCOPY K. R. Rodgers, I. Mukerji, V. Jayaraman, T. G. S&Q
Department of Chemistry, Princeton University, Princeton, NJ
08544
The advent of reliable pulsed lasers whose frequency can be shifted into the ultraviolet region has made possible the application of ultraviolet resonance Raman (UVRR) spectroscopy to biological molecules. For proteins, appropriate tuning of the laser yields selective enhancement of vibrational modes of the aromatic side chains phenylalanine, tyrosine, and tryptophan, or of the amide bonds. The spectra can provide information, at high sensitivity, about protein secondary structure, and about the local environment of aromatic residues. The experiment can also be applied in a time-resolved mode to monitor structural changes associated with transient processes. The R-T quaternary transition in hemoglobin is currently being studied in this manner, using one nanosecond laser to photolyze the CO adduct, and another to generate UVRR spectra. Changes in the tyrosine and tryptophan UVRR signals which develop 20 us after photolysis are attributed to the altered subunit contacts at the a& interface during the R-T rearrangement. A preceding alteration of the tryptophan signal is associated with interior tryptophan residues whose H-bonding is sensitive to helix-helix motions within the subunits. Thus the aromatic residue signals provide indicators of protein motions associated with both tertiary and quaternary rearrangements on the R-T pathway. Mutant and hybrid hemoglobins are providing fresh insights into these protein motions. 1. 2.
K. R. Rodgers, C. Su, S. Subramaniam, and T. G. Spiro, J. Am. Chem. Sot., 1992, 174, 3697. V. Jayaraman, K. R. Rodgers, I. Mukerji, and T. G. Spiro, Biochemistry, 1993 (in press).