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ISSN 1672-9145 Acta Biochim Biophys Sin 2004, 36(11): 724-728 CN 31-1940/Q

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Dynamics of Primary Events in the Photocycle of Excited Bacteriorhodopsin

Jun-Jun LU, Ming MING¹, Yi YANG, Jia WU¹, Bo LI, Jian-Dong DING¹, Qing-Guo LI², and Shi-Xiong QIAN*

Department of Physics, Fudan University, Shanghai 200433, China;

¹Department of Macromolecular Science, Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, China;

²Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai 200433, China

Abstract Transient dynamic behavior of the excited bacteriorhodopsin (BR), which was isolated from the strain H. salinarum, was studied at excitation wavelength from 585 to 639 nm. With the one-color femtosecond (fs) pump-probe technique, we revealed the primary events in BR's photocycle that took place in an ultrafast time scale. From the analysis of the decay components of the dynamical traces, it was evident that the isomerization of the retinal chromophore in BR and the intermediate J's formation occurred within 500 fs. BR exhibited pH-dependent dynamical behaviors. When the medium pH was between 5 and 9, the BR ultrafast dynamics has no obvious change. In contrast, the dynamical curves were obviously affected when the pH was out of that region.

Key words bacteriorhodopsin; transient dynamics; primary events; femtosecond laser; pump-probe technique

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Received: July 5, 2004 Accepted: September 29, 2004

This work was supported by the grants from the National Natural Science Foundation of China (No. 10274103, No. 20174006, No. 20221402, and No. 20374015)

*Corresponding author: Tel, 86-21-65642084; Fax, 86-21-65641344; Email, [email protected]