Diffractive optics-based heterodyne-detected four-wave mixing signals of protein motion: From “protein quakes” to ligand escape for myoglobin

Proceedings of the National Academy of Sciences of the United States of America - Tập 98 Số 11 - Trang 6110-6115 - 2001
Gami Dadusc1, Jennifer P. Ogilvie1, Peter J. Schulenberg1, Una Marvet1, R. J. Dwayne Miller1
1Department of Physics, University of Rochester, Rochester, NY 14627; and Departments of Physics and Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6

Tóm tắt

Ligand transport through myoglobin (Mb) has been observed by using optically heterodyne-detected transient grating spectroscopy. Experimental implementation using diffractive optics has provided unprecedented sensitivity for the study of protein motions by enabling the passive phase locking of the four beams that constitute the experiment, and an unambiguous separation of the Real and Imaginary parts of the signal. Ligand photodissociation of carboxymyoglobin (MbCO) induces a sequence of events involving the relaxation of the protein structure to accommodate ligand escape. These motions show up in the Real part of the signal. The ligand (CO) transport process involves an initial, small amplitude, change in volume, reflecting the transit time of the ligand through the protein, followed by a significantly larger volume change with ligand escape to the surrounding water. The latter process is well described by a single exponential process of 725 ± 15 ns at room temperature. The overall dynamics provide a distinctive signature that can be understood in the context of segmental protein fluctuations that aid ligand escape via a few specific cavities, and they suggest the existence of discrete escape pathways.

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Proceedings of the National Academy of Sciences of the United States of America

Tập 98 Số 11

6110-6115

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