Nonlinear Opitical Properties of Light-Induced Proton Transport in Bacteriorhodopsin for Real-Time Selective Detection of Motion

Elena Korchemskaya1 and Nikolai Burykin2

1Institute of Physics, National Academy of Sciences, Prospect Nauki 46, Kiev-39, 03039 Ukraine, and 2Institute of Applied Optics, National Academy of Sciences, Kudryavskaya St. 10g, Kiev-54, 01054 Ukraine

e-mail: elkorch@iop.kiev.ua
 

Now a biological photoreceptor and transmembrane photosensitive protein bacteriorhodopsin (bR) has attracted considerable interest in the area of analysis and detection of motion and small vibrations [1-5]. The processing cycle time of the photoelectric device based on bR is less than 1 ms [6, 7]. The most rapid processing time was obtained using photoelectric aspect of the proton transport in bR.

It is evident that proton transport in bR could be revealed also in novel nonlinear optical properties. It was shown in our previous studies on bR-film that when the intensities of the recording beams are equal, proton release is revealed in the sudden change in the intensity of the first-order self-diffraction beam in Raman-Nath conditions (thin holographic grating) [2, 3]. The kinetics of this sudden change in the first-order self-diffraction beam is similar to the photocurrent response under a stepwise change in light intensity [6, 7]. The processing cycle time based on nonlinear optical aspect of the proton transport in bR-films is also less than 1 ms. We have shown that very drastic increase in the first-order self-diffraction beam occurs under impulse shift of the interference pattern with respect to the holographic grating recorded in the bR-film. In this work, we propose to apply this drastic increase for the real-time selective detection of motion.

The present method enables a start and final of impulse shift to be detected with very high precision and time resolution less than 1 ms. A direction of motion is selectively detected.The value of sudden change in the first-order self-diffraction beam depends on the direction of motion. Once upward direction is initial, the higher value of sudden changes corresponds to upward direction than downward. Thus, even after a time it is possible to detect what the direction of motion was initial. The real-time selective detection of motion in present method can be directly observed on the oscillograph screen without the need for electrical amplification and computation circuits. Only He-Ne laser with wavelength 633 nm is used in our system, it makes possible the low-cost diode lasers also to be used. Thus, the purely optical device can be implemented for the real-time selective detection of motion.

Literature

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