Study on the spectrum response characteristic based on the wide type bacteriorhodopsin film

The photochromic retinal protein bacteriorhodopsin (BR) was found in the cell membrane of the Archaean Halobacterium salinarium. The excellent photochromic and photocycle properties of the BR provide the possibility of many applications in the filed of optical information processing. In this paper, the spectrum response characteristic of the wild type bacteriorhodopsin molecule film was studied by using pump-probe method. After the samples was excited by 532 nm YAG laser beam, the absorption spectra were probed by an optical fiber spectrum analysis (OSA). The absorption peaks at the ground state (B state) of the two samples are all at 562 nm wavelength. At 562 nm wavelength, the optical densities (OD) of the samples are about OD(WT1)(562 nm) = 2.04 and OD(WT2)(562 nm) = 1.37 respectively. The experiment results show that BRWT films have absorption that appears to strengthen with the probe time increasing in wavelength 550-650 nm, and this change phenomenon is described by spectra measured at different probe time. Appling the theoretical plot-fit of two exponentials to analyze the process of the absorption change it is found that this change includes two processes-fast process and slow process. Their corresponse time constants of BRWT1 are about 11 ms and 60 s, and those of BRWT2 about 24 and 30 s respectively