Elena Y. Korchemskaya

14-Fluoro-Bacteriorhodopsin Gelatin Films for Dynamic Holography Recording¶

Abstract The first dynamic holography recording using 14-fluoro-(14-F) bacteriorhodopsin (BR) gelatin films has been achieved. 14-F BR is an artificial BR pigment made by reconstitution of bacterioopsin (native BR without chromophore) with synthetic 14-F retinal. Low-intensity red light from a cw He-Ne laser was used for dynamic holography recording on the 14-F wild type (WT) BR and 14-F D96N mutant BR in gelatin films. There is not true comparing the diffraction efficiency for 14-F D96N BR and 14-F WT gelatin film, unlike the increased diffraction efficiency for D96N BR gelatin film with native chromophore relative to the WT BR gelatin film with native chromophore. Pre-illumination with blue light of the 14-F BR gelatin films significantly increases the diffraction efficiency of both the 14-F WT and the 14-F D96N BR pigments. The sequential application of blue and red laser beams indicates that 14-F BR gelatin films can be useful for optical memory.

Dynamic Holography in Bacteriorhodopsin/Gelatin Films: Effects of Light–Dark Adaptation at Different Humidity†

This work examines the kinetics of dynamic holography responses in light‐adapted and dark‐adapted bacteriorhodopsin (BR) films at different humidity. We have demonstrated that the kinetics of the diffraction efficiency in wild type BR films is quite different in dark‐adapted and light‐adapted samples. The holographic recording kinetics, which depends on the duration of incubation in the dark after light adaptation at different humidity values, was studied in depth. A specially designed miniature cell containing a BR film was mounted inside the holographic set up to allow controlled humidity changes over a broad range. The diffraction efficiency kinetics at humidity values of 96–99% were quite different from the kinetics at 60–93% humidity. We found that humidity values of 90–93% were most optimal for dynamic holography recording using a gelatin film containing BR. In agreement with a calculation of the wavelength‐dependent changes of the refractive index for dark‐adapted and light‐adapted BR samples using the Kramers–Kronig relation, the maximum difference in the refractive index and thus in the diffraction efficiency for dark‐adapted and light‐adapted BR films takes place at 630 nm, close to the wavelength of the He–Ne laser used.

Real-time selective image processing using photoinduced anisotropy of bacteriorhodopsin polymer films

Two different methods can be used for photoinduced anisotropy in the bacteriordopsin (BR) polymer films. The first method is based on the anisotropic properties of the initial photocycle form bR570, and second method is based on the anisotropic properties of the longest-lived photocycle intermediate M412. The mixed B-M-type photoinduced anisotropy holds much promise for an implementation of the devices capable of controlling light with light. The possibility of the application of BR polymer films for the light polarization modulator with purely optical control, photoanisotropic incoherent-to-incoherent optical conversion with concurrent spatial intensity filtration, and for logical image processing are shown.

Real-Time Optical Information Processing Through the Use of Low-Saturable Absorption in Bacteriorhodopsin Films

We have shown that the mechanism for a reversible anisotropic photoselection of bacteriorhodopsin (BR) molecules and a very small saturation intensity of a BR film allow for the blocking of any intensity feature from an image by just varying the intensity of a He-Ne laser beam without conventional frequency filters or rotation of an analyzer. It is found that the E204Q variant of BR offers additional valuable features. The photochemical cycle with a red-light absorbing O intermediate, B→M→O→B, and a distortion of the grating profile due to the low-saturation absorption are responsible for a large initial peak sharpness of the dynamic holographic recording kinetics.

DYNAMIC HOLOGRAPHY FOR STUDY OF NONLINEAR OPTICAL PROCESSES IN BIOLOGICAL PHOTORECEPTOR MOLECULE

It is proposed to apply dynamic holography method for exploring real-time phototransformations in the biological photoreceptor molecule. At dynamic holography grating recording, the interference of two coherent laser beams forms a modulation of the total light intensity at the sample plane. This leads to the space modulation of both absorption and refractive index in the sample and a dynamic holography grating is recorded. The dynamic holography is a zero background technique and it is possible to vary a special grating period from 0.2 to 100 micrometers in real time. The advantages of dynamic holography method for an investigation of functionally important processes in photoreceptor molecule are demonstrated with bacteriorhodopsin sample.

Holographic methods of detection and analysis of small vibrations using biological photoreceptor bacteriorhodopsin

The biological photoreceptor bacteriorhodopsin (bR) uses light energy to translocate protons across the cell membrane. The bR-films have spatial resolution does not fall below 5000 lines/mm, require no external processing, and may be cycled through the write/erase process more over millions of times without degradation. We have shown in Raman-Nath conditions (thin holographic grating) when the intensities of recording beams are equal, a very drastic increase in the first-order self-diffraction beam occurs under impulse shift. In this work, we propose to apply the kinetic characteristics of the first-order self-diffraction beam in thin holographic grating conditions on bR-film for real-time analysis of small vibrations and shocks. Oscillograms of these rapid vibrations are given. The processing cycle time is less than 1 ms. Detection and analysis of small vibrations and shocks in present method can be directly observed on the oscillograph screen without the need for electrical amplification and computation circuits. Only the He-Ne laser with wavelength 633 nm is used in our system, it makes possible the low-cost diode lasers also to be used.

Analysis of object motion by dynamic holography recording in bacteriorhodopsin films

It is proposed to combine the real-time testing of the dynamic holographic grating with self-diffraction registration of this grating in Raman-Nath conditions in order to detect the photorefractive variations which accompany the proton transport through the rigidly-held fragments of purple membranes containing biological photoreceptor bacteriorhodopsin (BR). The properties of superfast holographic recording on BR-films in Raman-Nath conditions are applied for an analysis of the object motion with cycle processing time of less than 1 ms. Whereas most of the holographic methods are based on dynamic holography recording in photorefractive materials with local response in Bragg conditions. The analysis of the object motion in the first-order diffracted beam in Raman-Nath self-diffraction conditions offers a number of advantages: 1 ) there is not the problem of the suppression of high undiffracted beam; 2) the registration of start and final of a object motion with very high precision; 3) the separation of the forward and reverse motions, even after a time it is possible to detect what motion direction was initial; 4) the low-frequency and high-frequency components of a object motion are selected and their mutual direction are determined. Keywords: biological photoreceptor bacteriorhodopsin (BR), polymer films with BR, proton release, Raman-Nath self-diffraction conditions, first-order diffracted beam, analysis of the object motion, motion direction separation, motion frequency selection.

Nonlinear polarization interaction in bacteriorhodopsin films with anisotropically saturating absorption

The effect of protein and matrix modifications on the photoanisotropic properties is studied for developing the concept of impact upon the main optical properties of the dynamic optical material based on bacteriorhodopsin (BR) both interaction of transmembrane protein--chromophore complex BR with matrix and interaction of protein opsin with chromophore retinal. Also possibility of the application of BR-films for the light polarization modulator is proposed.

Real-Time Probing the Biological Processes by Holographic Recording in Polarization-Sensitive Bacteriorhodopsin Films

Bacteriorhodopsin is a photosensitive protein similar to visual rhodopsin. We propose to apply photoinduced anisotropy and holographic recording in bacteriorhodopsin films for real-time analysis of the biological tissue image and study of retina dark adaptation. Article not available.

B-M-type anisotropy in bacteriorhodopsin films for nonlinear spatial light modulation

Bacteriorhodopsin (BR), a photoreceptor protein possesses a photochemical cycle of several distinct intermediates; all of them are photoactive. The BR molecules both in the initial form of the photocycle, BR570 (absorption maximum around 570 nm) and longest-lived (in films) intermediate M412 (absorption maximum at 412 nm) possess anisotropic absorption. Under the action of linearly polarized light, the reversible anisotropic photoselection of BR molecules takes place. So far only the method of photoinduced anisotropy based on anisotropic properties of BR570 was applied to realtime optical processing. In the present work, the potentialities for the use of photoinduced anisotropy in the BR-films based on both BR570 and M412 for the spatial light modulation are demonstrated. The overall blocking of highintensity features from an image is shown. Mixed B-M-type anisotropy in the chemically modified BR films, as applied to the edge enhancement, can provide a contrast ratio as high as 250:1. Low saturation intensity of the BR-films allows for the blocking of any intensity feature from an image that is carried out by choosing an appropriate intensity level of a controlling He-Ne laser beam without analyzer rotation. The photoanisotropic incoherent-to-coherent optical conversion with concurrent spatial-intensity modulation is also performed on the BR-films.