Bacteriorhodopsin Films Research Articles

Bioelectronic Imaging Array Based on Bacteriorhodopsin Film

A photoreceptor array that exploits the light sensitive bacteriorhodopsin (bR) films has been manufactured on a flexible indium-tin-oxide (ITO) coated plastic film using electrophoretic sedimentation technique (EPS). The effective sensing area of each photoreceptor is 2 x 2 mm (2), separated by 1 mm and arranged in a 4 x 4 array. A switched integrator with gain on the order of 10(10) is used to amplify the signal to a suitable level. When exposed to light, the differential response characteristic is attributed to charge displacement and recombination within bR molecules, as well as loading effects of the attached amplifier. The peak spectral response occurs at 568 nm and is linear over the tested light power range of 200 mu W to 12 mW. The response remains linear at other tested wavelengths, but with reduced amplitude. Initial tests have indicated that responsivity among all photoreceptors is greater than 71% of the average value, 465.25 mV/mW. The differential nature of the signal generated by bR makes it a suitable sensing material for vision applications such as motion detection. The prototype array demonstrates this property by employing Reichardt's delay-and-correlate algorithm. Furthermore, fabricating sensor arrays on flexible substrates introduces a new design approach that enables non-planar imaging surfaces.

An all-optical time-delay relay based on a bacteriorhodopsin film

Using a special property of dynamic complementary-suppression-modulated transmission (DCSMT) in the bacteriorhodopsin (bR) film, we have demonstrated an all-optical time-delay relay. To extend our work, the relationship between the delay time of the all-optical time-delay relay and parameters of a bR film is numerically studied. We show how the delay time changes with the product of concentration and thickness (PCT) of a bR film. Furthermore, the shortest and longest delay times are given for the relay of ‘switch off’. The saturable delay time and maximum delay-time of ‘switch on’ are also given. How the wavelengths (632.8, 568, 533 and 412 nm) and intensities of the illuminating light influence the delay time is also discussed. The simulation results are useful for optimizing the design of all-optical time-delay relays.

Application of bacteriorhodopsin film for polarization phase-shifting interferometry

Photoinduced anisotropy in bacteriorhodopsin (BR) film is based on photoanisotropic selective bleaching of BR molecules under linearly polarized excitation light. It is modulated by the polarization orientation of the linearly polarized light. The anisotropic information recorded in the BR film is read by a circularly polarized light, which is in turn converted into an elliptical polarized light by the BR film. The rotation angle and the ellipticity of the elliptical polarized light are dependent on the polarization orientation of the linearly polarized excitation light. A phase-shifting interferometer based on the photoinduced anisotropy of BR film is presented theoretically and experimentally. Phase shift is controlled by the polarization orientation of the external excitation light, thus, the phase shift can be controlled without moving parts inside the interferometer, which contributes to the mechanical stability of the system.

Kinetics of photoinduced anisotropy in bacteriorhodopsin film under two pumping beams

Photoinduced anisotropy in bacteriorhodopsin (BR) film arises from the selective bleaching of BR molecules to linearly polarized light. The kinetics of photoinduced anisotropy excited by single and two pumping beams are investigated theoretically and experimentally. Compared with a single pumping beam (650 nm), which produces comparatively small photoinduced anisotropy, dual-wavelength linearly polarized pumping beams (650 and 405 nm) can obviously change the photoinduced anisotropy. When the polarization orientation of the 405 nm pumping beam is perpendicular to that of the 650 nm pumping beam, the peak and steady values of the photoinduced anisotropy kinetic curves are remarkably enhanced. But when the two pumping beams have parallel polarization orientation, the peak and steady values are restrained. At a fixed intensity of the 650 nm pumping beam, there exists an optimal intensity for the 405 nm pumping beam to maximize the value of the photoinduced anisotropy. The photoinduced transmittance of the polarizer-BR-analyzer system is modulated by the polarization angle of the 405 nm pumping beam in an approximate-cosine form.

All-optical continuous-tunable image switch based on nonlinear photoinduced anisotropy in bacteriorhodopsin film

Using nonlinear photoinduced anisotropy in bacteriorhodopsin (bR) film, we presented and demonstrated an image switch in which the output can be tuned continuously by the intensity of a pumping beam. A laser with wavelength 532 nm was used as the pumping beam, and a He–Ne laser at wavelength 632.8 nm was used as the probe beam. Without pumping light, a little of polarized probe beam can transmit the crossed polarizers and the output is very low. With the presence of pumping light, owing to photoinduced anisotropy in the bR film, a portion of the probe beam transmits the crossed polarizers, depending on the intensity of the pumping beam. For the low-intensity probe beam (0.44 mW/cm 2), the output is dependent on a wide range of pumping beam (2–30 mW/cm 2). On the contrary, for the high-intensity probe beam (0.80 mW/cm 2), the output is dependent on a narrow range of pumping beam (2–7 mW/cm 2).

Thermochromism of Bacteriorhodopsin and Its pH Dependence

Purple membranes (PMs), which consist of the photochromic membrane protein bacteriorhodopsin (BR) and lipids only, show complex thermochromic properties. Three different types of reversible temperature-dependent spectral transitions were found, involving spectral states absorbing at 460, 519, and 630 nm. These thermochromic absorption changes were analyzed in the range from 10 to 80 degrees C. In dependence on the bulk pH value, hypsochromic or bathochromic shifts in the BR absorption spectra are observed in BR gels as well as in BR films. The thermochromic changes between both purple and blue or purple and red were quantified in the CIE color system. The molecular changes causing these effects are discussed, and a model is presented in terms of intramolecular protonation equilibriums. The thermochromic properties of BR may be of interest in applications like security tags, as this feature may complement the well-known photochromic properties of BR.

Influence of polarization orientation of violet light on the diffraction efficiency of bacteriorhodopsin

When a grating is recorded in a bacteriorhodopsin film by two linear parallel polarized beams together with an auxiliary violet light, the diffraction efficiency has a dependence on the polarization orientation of the violet light as well as its intensity. A method for calculating the diffraction efficiency of gratings in bacteriorhodopsin is proposed based on the two-state photochromic model, considering the saturation effect and the polarization status of all the involved lights. It is found that the polarization orientation of the violet light produces an approximate-cosine and an approximate-sine modulation on the steady-state diffraction efficiency separately at low and high intensities, respectively. The parallel polarized violet light can improve the steady-state diffraction efficiency to a larger degree than the perpendicularly polarized violet light when both are at their optimal intensities. The optimal intensity for the parallel polarized violet light is lower than that of the perpendicular polarized one. Thus, the improvement of the steady-state diffraction efficiency is less sensitive to the intensity of perpendicular polarized violet light than to that of parallel polarized violet light.

Matrix influence on the optical response of composite bacteriorhodopsin films to ammonia

The practical fabrication of thin-film chemical sensors generally requires the responsive element to be embedded in a matrix. The influence of different organic and inorganic matrices (polyvinyl alcohol (PVA), gelatin, and silica) on the static and dynamic optical properties of bacteriorhodopsin (bR)-containing films, including their responses to ammonia, were studied. Morphological and cross-sectional studies of the bR-containing films using atomic force microscopy, scanning electron microscopy, and energy dispersive spectroscopy revealed a uniform distribution of the bR within the films; the silica films were much rougher and more porous than those made with the polymers; gelatin tended to suppress the ammonia response (because of its amine groups); PVA and silica greatly slowed down the photocycle (because of their hydroxyl groups). The silica-based film had the fastest and most sensitive response to ammonia.

Effect of reconstruction beam polarization on the kinetics of anisotropic gratings in bacteriorhodopsin

Anisotropic gratings are recorded on bacteriorhodopsin films by two parallelly polarized beams, and the effect of the polarization orientation of the reconstructing beam on the diffraction efficiency kinetics is studied. A theoretical model for the diffraction efficiency kinetics of the anisotropic grating is developed by combining Jones-matrix and photochromic two-state theory. It is found that the polarization azimuth of the reconstructing beam produces a cosine modulation on the kinetics of the diffraction efficiency, being positive at the peak efficiency and negative for steady state. By adding auxiliary violet light during grating formation, the saturation of the grating can be restrained. As a result, the negative cosine modulation for the steady-state diffraction efficiency changes to a positive one. In addition, the steady-state diffraction efficiency is increased appreciably for all reconstructing polarization orientations.

Influence of auxiliary violet light on holographic kinetics at low and high recording intensities in bacteriorhodopsin film

The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the saturation absorption and the scattering and reflecting lights from the BR film, the grating contrast-ratio of the hologram is diminished during the hologram recording. When the intensity of the recording light is low, the influence of the saturation absorption and the scatter and reflection of BR film on the grating contrast-ratio is weak. But for the case of intense recording light, this influence is more serious. It is found that the influence of the auxiliary violet light on the holographic kinetics of diffraction efficiency is distinct under different recording intensities. At the low recording light intensity, the steady diffraction efficiency is increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency and the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-state model of BR photochromism, we give a good theoretical explanation to the above phenomena.

Influence of auxiliary violet light on holographic diffraction efficiency under different recording intensities in bacteriorhodopsin film

The photochromic bacteriorhodopsin (BR) film can be used as a rewritable holographic recording medium. Due to the scattering and the reflecting of light from the BR film, the grating contrast of the hologram is diminished during the hologram recording. When the intensity of the recording light is weak, the influence of the scattering and reflection on the grating contrast is low enough to be neglected. But in the case of intense recording light, this influence should not be overlooked. It is found that the influence of the auxiliary violet light on the holographic diffraction efficiency kinetics is distinct under different recording intensities. At weak recording light intensities, the steady diffraction efficiency are increased and the peak diffraction efficiency is suppressed by the auxiliary violet light. But for intense recording light, the steady diffraction efficiency as well as the peak diffraction efficiency are both increased by the auxiliary violet light. Based on the two-level model of BR photochromism, we give a good theoretical explanation to the above phenomena.

Modulation of the azimuth of polarization of reconstruction beam on the diffraction efficiency of anisotropic gratings recorded in bacteriorhodopsin films by two parallel linearly polarized beams

When the linearly polarized object and reference beams with the same polarization direction are used for recording gratings in bacteriorhodopsin films, the azimuth of polarization of the reconstruction beam has an influence on the diffraction efficiency. By using Jones matrices to analyze this phenomenon, we find that the azimuth of polarization of the reconstruction beam makes a cosine modulation on the diffraction efficiency. The diffracted beam is linearly polarized only when the polarization of the reconstruction beam is parallel or perpendicular to that of the recording beams; otherwise, the diffracted beam becomes elliptically polarized. The azimuth of polarization of the reconstruction beam produces a positive cosine modulation on the peak diffraction efficiency, but a negative cosine modulation on the steady diffraction efficiency (with phase difference π). By adding auxiliary violet light during grating formation, the saturation of the grating can be restrained; as a result, the negative cosine modulation of the steady diffraction efficiency changes to the positive cosine modulation and also the steady diffraction efficiency is increased apparently.

Bacteriorhodopsin—Perspective biomaterial for molecular nanophotonics

Results of investigation of photochromic protein bacteriorhodopsin (BR) extracted from cellular membranes of Halobacterium salinarum are represented. Basic processes and original approaches of neural networks realization based on bacteriorhodopsin in composition of multilayer structures. Requirements of BR-containing functional films are determined and results of investigation of layers modifications are represented for the purpose of stabilization of extremely high photochromic sensitivity of BR-containing media. The modification of BR-films using bifunctional crosslinking reagents to increase of technological parameters of BR is applied. The influence of 1,4-diaminobenzene, glutaric dialdehyde and lysine on photochromic properties of the bacteriorhodopsin films is investigated. Shown that addition of bifunctional crosslinking reagents increase technological parameters of materials based on bacteriorhodopsin.

Theoretical approach to photoinduced inhomogeneous anisotropy in bacteriorhodopsin films

The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance was found between both sets of data. The theoretical approach shows that the values of the rate constants for solid bR films are about two or three orders of magnitude lower than those observed in solution. It can also be noted that the temperature change during the experiment had a great influence on the final values of transmittance and, consequently, on the inhomogeneous distribution along the coordinate of light propagation. The study shows that, depending on the intensity and wavelength of the pump beam, we can obtain a very inhomogeneous profile of the population densities, which implies an inhomogeneous profile of the birefringence and dichroism. Therefore, this must be taken into account in the applications described for this system.

Bacteriorhodopsin photocycle at cryogenic temperatures reveals distributed barriers of conformational substates

The time course of thermal reactions after illumination of 100% humidified bacteriorhodopsin films was followed with FTIR spectroscopy between 125 and 195 K. We monitored the conversion of the initial photoproduct, K, to the next, L intermediate, and a shunt reaction of the L state directly back to the initial BR state. Both reactions can be described by either multiexponential kinetics, which would lead to apparent end-state mixtures that contain increasing amounts of the product, i.e., L or BR, with increasing temperature, or distributed kinetics. Conventional kinetic schemes that could account for the partial conversion require reversible reactions, branching, or parallel cycles. These possibilities were tested by producing K or L and monitoring their interconversion at a single temperature and by shifting the temperature upward or downward after an initial incubation and after their redistribution. The results are inconsistent with any conventional scheme. Instead, we attribute the partial conversions to the other alternative, distributed kinetics, observed previously in myoglobin, which arise from an ensemble of frozen conformational substates at the cryogenic temperatures. In this case, the time course of the reactions reflects the progressive depletion of distinct microscopic substates in the order of their increasing activation barriers, with a distribution width for K to L reaction of approximately 7 kJ/mol.

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.

Measurements of photoinduced refractive index changes in bacteriorhodopsin films

We report the pump-probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is based on a convenient and accurate determination of optical path difference using digital interferometry-based local fringe shift. The results are presented for the wild-type as well as genetically modified D96N variant of the bacteriorhodopsin.

2P254 脂肪酸上に積層したジミリストイルフォスファチジルコリンとバクテリオロドプシンの複合薄膜(生体膜・人工膜(構造・物性),ポスター発表,第45回日本生物物理学会年会)

2P254 脂肪酸上に積層したジミリストイルフォスファチジルコリンとバクテリオロドプシンの複合薄膜(生体膜・人工膜(構造・物性),ポスター発表,第45回日本生物物理学会年会)

Simulation of effect of non-uniform input image on characteristics of output image of optical novelty filter based bacteriorhodopsin film

Simulation of effect of non-uniform input image on characteristics of output image of optical novelty filter based bacteriorhodopsin film

Study on the lifetime of M-intermediate of bacteriorhodopsin film chemically modified with CeO 2 nanoparticles

The characteristics of intermediates of bacteriorhodopsin (bR) can be verified by chemical modification of its surroundings. CeO 2 nanoparticles, which were obtained using water-in-oil (W/O) microemulsion and calcined at various temperatures, were used as chemical additive for the modification of bR. X-ray diffraction (XRD) shows that the mean particle sizes for the samples calcined at 500 and 800 °C are approximately 10 and 30 nm, respectively. We prepared CeO 2 nanoparticle modified poly(vinyl alcohol) (bR-PVA) films with an optical density of about 1.5 at the ground state. It is observed that the lifetime of the M-intermediate for the modified films is prolonged compared with that of the unmodified ones, and the lifetime increases with decreasing particle size. A probable mechanism, which is likely to involve effective molecular interactions between the CeO 2 nanoparticles and the bR molecules, is discussed. The hydroxyl groups, which might arise from the interaction between the nanoparticles and the surrounding water molecules, help to lower the ability of the Schiff base of uptaking protons in the M-intermediate. The results indicate that controlling the interactions between biomolecules and various nanomaterials would enlarge the functionality and the range of the application of nanoparticles.