This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Whitmire, S. E. Articles by Birge, R. R. Search for Related Content PubMed PubMed Citation Articles by Whitmire, S. E. Articles by Birge, R. R.

Protein Flexibility and Conformational State: A Comparison of Collective Vibrational Modes of Wild-Type and D96N Bacteriorhodopsin

S. E. Whitmire ^*, D. Wolpert ^*, A. G. Markelz ^*, J. R. Hillebrecht , J. Galan  and R. R. Birge 

^*Physics Department, University at Buffalo, State University of New York, Buffalo, New York; and Departments of Chemistry and of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut

Correspondence: Address reprint requests to A. G. Markelz, E-mail: amarkelz{at}buffalo.edu.

Far infrared (FIR) spectral measurements of wild-type (WT) and D96N mutant bacteriorhodopsin thin films have been carried out using terahertz time domain spectroscopy as a function of hydration, temperature, and conformational state. The results are compared to calculated spectra generated via normal mode analyses using CHARMM. We find that the FIR absorbance is slowly increasing with frequency and without strong narrow features over the range of 2–60 cm^-1 and up to a resolution of 0.17 cm^-1. The broad absorption shifts in frequency with decreasing temperature as expected with a strongly anharmonic potential and in agreement with neutron inelastic scattering results. Decreasing hydration shifts the absorption to higher frequencies, possibly resulting from decreased coupling mediated by the interior water molecules. Ground-state FIR absorbances have nearly identical frequency dependence, with the mutant having less optical density than the WT. In the M state, the FIR absorbance of the WT increases whereas there is no change for D96N. These results represent the first measurement of FIR absorbance change as a function of conformational state.

This article has been cited by other articles:

				L. Zhou and S. A. Siegelbaum Effects of Surface Water on Protein Dynamics Studied by a Novel Coarse-Grained Normal Mode Approach Biophys. J., May 1, 2008; 94(9): 3461 - 3474. [Abstract] [Full Text] [PDF]

				R. Balu, H. Zhang, E. Zukowski, J.-Y. Chen, A. G. Markelz, and S. K. Gregurick Terahertz Spectroscopy of Bacteriorhodopsin and Rhodopsin: Similarities and Differences Biophys. J., April 15, 2008; 94(8): 3217 - 3226. [Abstract] [Full Text] [PDF]

				N. Laman, S. S. Harsha, D. Grischkowsky, and J. S. Melinger High-Resolution Waveguide THz Spectroscopy of Biological Molecules Biophys. J., February 1, 2008; 94(3): 1010 - 1020. [Abstract] [Full Text] [PDF]

				U. Heugen, G. Schwaab, E. Brundermann, M. Heyden, X. Yu, D. M. Leitner, and M. Havenith Solute-induced retardation of water dynamics probed directly by terahertz spectroscopy PNAS, August 15, 2006; 103(33): 12301 - 12306. [Abstract] [Full Text] [PDF]

				J. Xu, K. W. Plaxco, and S. J. Allen Probing the collective vibrational dynamics of a protein in liquid water by terahertz absorption spectroscopy. Protein Sci., May 1, 2006; 15(5): 1175 - 1181. [Abstract] [Full Text] [PDF]

				J. Knab, J.-Y. Chen, and A. Markelz Hydration Dependence of Conformational Dielectric Relaxation of Lysozyme Biophys. J., April 1, 2006; 90(7): 2576 - 2581. [Abstract] [Full Text] [PDF]