ABSTRACT
BR-D96N was a genetically mutated product of bacteriorhodopsin (BR) with obvious improved photochromic effect. Compared with the wild type BR, BR-D96N had a lifetime of M state prolonged to 5 min, showing obvious saturation absorption and lower light intensity in saturation absorption (0.4 mW/cm(2)). In case of holographic recording, dynamic grating was recorded in the BR-D96N film, its characteristic parameter was not light exposure energy but light intensity. The writing time of the holographic grating depended on the recording light intensity. The higher the recording light intensity, the faster the grating builds up. Under a weak reconstruction light, the recording light intensity resulting in maximal diffraction efficiency was consistent with the saturation absorption intensity. The reconstruction light could partly erase the grating. With lower intensity of reconstruction light, higher diffraction efficiency (1.8%) could be reached, but the diffraction intensity was not high. To get highest diffraction intensity, a properly high intensity of reconstruction light was needed (80 microW/cm(2)). The result of these experiments showed that holographic images could be recorded on the BR-D96N film.
Subject(s)
Bacteriorhodopsins , Holography , Bacteriorhodopsins/genetics , Light , Point Mutation , X-Ray DiffractionABSTRACT
Based on experimental measurement of the pulse response of the bacteriorhodopsin (BR) film photocell, the impact response function of the device is obtained by data fitting with MATLAB software. A simulation system is accordingly built with the SIMULINK module. The output response signals of the BR film photocell under different stepping incident light are calculated based on this simulation system. It is concluded that the differential response described before (which occurs in milliseconds to seconds, outputs a positive pulse when light is on, and outputs a negative pulse when light is off) was not the intrinsic property of the BR molecule, but was partially caused by the measuring circuit. The differential response caused by the intrinsic property of the BR molecule happened in microsecond time scale, and it produced a negative pulse when light is on and a positive pulse when light is off. The mechanisms of the two types of differential responses are discussed.
Subject(s)
Bacterial Proteins/chemistry , Bacteriorhodopsins/chemistry , Halobacterium salinarum/chemistry , Computer Simulation , Halobacterium salinarum/metabolism , PhotochemistryABSTRACT
Oriented bacteriorhodopsin films were prepared on ITO conductive glass by using electrophoretic or Langmuir-Blodgett methods to construct photocells. Pulse response photovoltages under stimulation of pulsed laser and differentialresponse signals under irradiation of discontinued light were respectively measured, and the origins of the two responses and their correlation are analyzed. The pulse response photovoltage initiated from the ultrafast charge separation of the retinal and the proton translocation, followed by the deprotonation and reprotonation of the Schiff base and its surrounding amino acids. This was a quick response and was the preceding reaction of the differential response. The differential response was caused by the charging and discharging of the continuous proton current of the BR light-driven proton pump at the light-on and light-off, as well as the coupling mode of the measuring circuit, which was a slow process.
