共查询到20条相似文献,搜索用时 0 毫秒
1.
D. Oesterhelt 《Nachrichten aus der Chemie》1974,22(22):475-476
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细菌视紫红质的光吸收特性 总被引:1,自引:0,他引:1
细菌视紫红质 ( BR)是存在于嗜盐菌紫膜中唯一的蛋白质 ,是一种高稳定性的光敏生物材料 [1~ 3] .当光照时 ,它吸收光子后会发生可逆光敏异构化 (见示意图 ) .在这一光循环反应中包含一系列的中间体 (表示为 J-、K-、L -、M-、N-和 O-态 ) ,在这些中间体的转变中完成质子的传输 . BR光敏异构化到 L态会导致去质子化 .异构化过程中 ,希夫碱基的质子传递到 ASP85残基 ,完成了质子的释放 ;随后异构化成 O态 ,又从 ASP96残基上获得质子生成最初的 BR,实现质子的获取 [4 ,5] ,又回到原始状态 .在光循环过程中 ,BR把质子从膜内运到膜外 .… 相似文献
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《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1990,23(1):45-63
Current-voltage dependences for different tentative bacteriorhodopsin models were studied in order to explain the linearity of this dependence observed in our previous experiments. It is proved that the best correspondence with experiment occurs when the passive proton transport path is assumed to contain many binding sites and the thickness of the widest barrier separating these sites is not more than 1 nm. One of the following two conditions is necessary: (1) electrostatic repulsion of protons in the channel is so strong that not more than one proton can be in the channel at a time; the potential energy of a proton in this channel decreases linearly towards the active site. (2) Electrostatic repulsion between protons in the channel is moderate, and the binding energy of a proton at all channel sites is equal. Under conditions of high channel occupation, single-file effects lead to non-linearity of the current-voltage characteristics if there is no electrostatic repulsion. 相似文献
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Saurav Misra Charles Martin Oh-Hoon Kwon† Thomas G. Ebrey‡ Ning Chen Rosalie K. Crouch Donald R. Menick 《Photochemistry and photobiology》1997,66(6):774-783
Abstract— Arginine 134 is located near the extracellular surface of bacteriorhodopsin (bR) and may interact with one or more nearby glutamate residues. In the bR mutant R134K, light-induced Schiff-base deprotonation (formation of the M intermediate) exhibits several kinetic components and has a complex pH dependence. The kinetics and pH dependence of M formation were analyzed using the following general guidelines for interpreting M formation: (1) The fastest component of M formation reflects the redistribution of the Schiff-base proton to D85, the usual proton acceptor, in response to the change in the proton affinities of the Schiff base and D85 early in the photocycle; (2) Two additional components of M formation reflect transitions between spectroscopically similar substates of M. By applying these guidelines, supplemented by information about the pKa s of D85 and the proton release group from acid (purple-to-blue) and alkaline titrations of the absorption spectra of the unphotolyzed R134K pigment, we explain the pH dependence of M formation as being due to titration of the counter-ion, D85, and of the proton release group. We calculate, in R134K, that the pKa of D85 is 4.6 in the unphotolyzed state, while the pKa of the proton release group is 8.0 in the unphotolyzed state but drops to ∽5.8 in the M intermediate. The same value for the pKa of the proton release group in the M intermediate is obtained when we use photocurrent measurements to monitor proton release.
The altered values of these pKa s relative to the corresponding values in wild-type bR suggest that D85 and the proton release group are coupled more weakly in R134K than in the wild type. 相似文献
The altered values of these pK
5.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
6.
PAN Kai LIU Zhao-yue WANG Geng BAI Yu-bai LI Tie-jin 《高等学校化学研究》2006,22(4):484-487
IntroductionIn recent years, dye-sensitized solar cells(DSSCs) have attracted more and more attention be-cause of their low cost and simple fabrication[1—3].They are made of four parts: a photo-electrode, a dyesensitizer, an electrolyte and a counter-ele… 相似文献
7.
Alain Chaumont Dr. Marcel Baer Gerald Mathias Dr. Dominik Marx Prof. 《Chemphyschem》2008,9(18):2751-2758
The protein bacteriorhodopsin pumps protons across a bacterial membrane; its pumping cycle is triggered by the photoisomerization of a retinal cofactor and involves multiple proton‐transfer reactions between intermittent protonation sites. These transfers are either direct or mediated by hydrogen‐bonded networks, which may include internal water molecules. The terminal step of the proton‐transfer sequence is the proton release from a pocket near Glu194 and Glu204 to the extracellular bulk during the transition from the L to the M photointermediate states. The polar and charged side chains connecting these two regions in the crystal structures show no structural changes between the initial bR state and the L/M states, and no intermittent protonation changes have been detected so far in this region. Based on biomolecular simulations, we propose two potential proton‐release channels, which connect the release pocket to the extracellular medium. In simulations of the L photointermediate we observe bulk water entering these channels and forming transient hydrogen‐bonded networks, which could serve as fast deprotonation pathways from the release pocket to the bulk via a Grotthuss mechanism. For the first channel, we find that the triple Arg7, Glu9, and Tyr79 acts as a valve, thereby gating water uptake and release. The second channel has two release paths, which split at the position Asn76/Pro77 underneath the release group. Here, water molecules either exchange directly with the bulk or diffuse within the protein towards Arg 134/Lys129, where the exchange with the bulk occurs. 相似文献
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Over the past five years, photoelectrochemical detection as an analytical technique has been increasing in importance. Contributing factors in this new popularity are the rapid and unique reactions possible with photochemistry, and the superior selectivity and sensitivity of electrochemical detection. 相似文献
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Yi-Fan RUAN Nan ZHANG Yuan-Cheng ZHU Wei-Wei ZHAO Jing-Juan XU Hong-Yuan CHEN 《物理化学学报》2017,33(3):476-485
光电化学生物分析是近年来新出现并发展迅速的一种分析技术,其检测原理是基于在光照下识别元件和目标分子之间的生物识别作用造成光电活性物质产生的电信号的改变,以实现对待测物的定量测定。由于其灵敏选择性检测的优点及其在生物分析中的巨大潜力,该方法吸引了较多的关注,并且在检测性能和生物传感应用等方面也取得了较大进步。本文针对光电化学生物分析中常见的四种应用领域,即直接光电化学检测、光电化学酶检测、光电化学核酸检测以及光电化学免疫分析,综述了近年来国内外在光电化学生物分析研究领域的最新进展,并对其未来发展进行了展望。 相似文献
14.
Anna B. Druzhko † David J. Vanderah Baldwin Robertson Howard H. Weetall 《Photochemistry and photobiology》1996,64(5):867-869
Abstract— The photoinduced changes of absorbance as well as proton release and uptake have been observed for an azulenic analog of wild-type bacteriorhodopsin. The release and uptake of protons have been measured using a highly sensitive electrochemical technique. Bacteriorhodopsin membrane patches on a tin-oxide electrode produce a transient photocurrent that is negative for proton release and positive for proton uptake. For azulenic bacteriorhodopsin the photocurrent is approximately 20% of the transient observed with native bacteriorhodopsin. The existence of the photoinduced absorbance changes and the transient photocurrent are important results for gaining further insight into the photoinduced function of bacteriorhodopsin. 相似文献
15.
FU Xue-qi ̄ LI Zheng-qiang ̄ WANG Jin-dui ̄ WANG BaO-huia LI Bo-fu ̄ LI Tie-jin ̄ 《高等学校化学研究》1995,11(3):215-218
StudiesonHEPESStabilizingMIntermediateofBacteriorhodopsinFUXue-qi ̄1,LIZheng-qiang ̄2,WANGJin-dui ̄1,WANGBaO-huia,LIBo-fu ̄2andLI... 相似文献
16.
Ting Li Hui Dong Yuanqiang Hao Yintang Zhang Shu Chen Maotian Xu Yanli Zhou 《Electroanalysis》2022,34(6):956-965
Near-infrared (NIR) light-driven photoelectrochemical (PEC) sensing is a highly promising analytical technique, especially for in situ bioanalysis, due to the deep penetration capability and minimal invasiveness of NIR light. In this mini review, we provide a brief overview of recently developed NIR PEC sensors, focusing on NIR light-responsive materials and the representative applications of this type of PEC sensor. Future perspectives for NIR PEC sensors are also described. 相似文献
17.
Mahmoud M. Khader Mahmoud M. Saleh Emad M. El-Naggar 《Journal of Solid State Electrochemistry》1998,2(3):170-175
Active ferric tungstate was prepared by fusing an equimolar mixture of tungsten oxide and ferric oxide at 1100 °C and annealing
at 800 °C for 20 h. Analysis of the electrode material by X-ray diffraction showed that its composition was Fe2WO6. When this material was illuminated by visible light in 0.1 M NaOH solution, an anodic photocurrent at a positive potential
of 0.5 V (SCE) was obtained. Therefore, this material is considered as an n-type semiconductor. The d.c. conductivity of this
material at 25 °C was 4 × 10−6 Ω−1 cm−1. In the dark, unexpectedly high anodic currents were observed at positive potentials of 0.8 V (SCE) in 0.1 M NaOH. These
currents are attributed to the existence of a high density of electron-hole recombination centers within the band-gap of ferric
tungstate. When dimethyl viologen (DMV) was used as an electroactive compound in the electrolyte, the anodic photocurrents
increased significantly. The oxidation of DMV is thus expected to compete with the electron-hole recombination process. Furthermore,
the process of electron-hole recombination was also predicted from the shape of the photocurrent transients under interrupted
illumination. These transients exhibited first-order relaxation effects in the region of the onset time of the photocurrents.
The band-gap energy of Fe2WO6 was found to be about 1.5 eV and its flat-band potential in 0.1 M NaOH was about −0.3 V (SCE). The photoelectrochemical properties
of ferric tungstate are explained according to the formalism of the band model of the semiconductor/electrolyte interface.
Received: 16 July 1997 / Accepted: 26 September 1997 相似文献
18.
The application of organically modified sol–gel glass (ORMOSIL) for stabilizing D96N bacteriorhodopsin is reported. The ormosil sandwiched bacteriorhodopsin shows high stability and better photoactivity than those made under similar conditions without ormosil. Three approaches for immobilizing Bacteriorhodopsin (BR) on either quartz plate or antimony tin oxide (ATO) electrode were investigated. System-1 was made by drying the BR preparation under ambient conditions. System-2 was made by drying the same amount of BR followed by sandwiching the dried BR suspension using a transparent ORMOSIL layer whereas system-3 was made by drying the BR suspension over a transparent layer of ormosil followed by the deposition of another layer of transparent ormosil over the dried BR, thus sandwiching BR between two layers of ORMOSILS. The transparent ormosil layer was made in aqueous acidic medium using 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The characteristics of these three systems based on visual photography, UV-VIS spectroscopy (both in the presence and absence of external light) and photoelectrochemistry are reported. UV-VIS spectroscopy revealed excellent performance of BR when sandwiched between two layers of ORMOSILS (system-3) both in terms of photoactivity and stability for practical applications. The photo-electrochemistry of these three systems deposited on ATO electrodes is also reported. The photocurrent as a function of applied potential was recorded in the presence and absence of external light. The photocurrent showed increasing magnitude at negative potential and decreased from system-1 to system-3. The stability of ormosil sandwiched bacteriorhodopsin was found to exceed 1.5 years for practical applications. 相似文献
19.
利用飞秒时间分辨吸收光谱方法研究了菌紫质(BR)光循环中视黄醛超快异构化反应过程. 发展了结合全局拟合的奇异值分解(SVD)分析方法, 建立了超快异构化反应动力学模型, 解析了几个重要的中间态I460, J625和K590的物种相关差异光谱(SADS)和布居动力学, 确定了光致异构化反应过程. 同时明确了700 nm附近存在的受激荧光来自于弗兰克-康登跃迁态(H中间态)的贡献, 其衰减寿命为0.04 ps. 这些结果对深入认识H态在超快异构化反应过程中的作用具有参考价值. 相似文献
20.
建立了光电化学系统竞争性检测生物素(Biotin)小分子浓度的方法。采用联吡啶钌[Tris(2,2’-bipyridine)ruthenium,Ru-bpy)]作为标记物,以氧化锡纳米颗粒为电极,草酸盐为电子供体还原标记物。在470 nm光激发下,联吡啶钌的外层电子吸收能量后由基态变为激发态,注入半导体氧化锡纳米颗粒电极的导带,形成光电流信号;草酸盐还原失去电子的联吡啶钌使其恢复初始状态,从而可以再次作为电子供体受激发产生光电流信号。在竞争性检测生物素(Biotin)浓度时,亲和素(Avidin)吸附到氧化锡纳米颗粒电极表面作为识别元件,在浓度大于0.5 g/L时能够达到最大的电极表面覆盖率。1μmol/L Ru-bpy-biotin与不同浓度Biotin组成的混合溶液与电极表面的Avidin发生亲和反应,光激发后检测光电流大小;当溶液中Biotin的浓度增加时,致使与电极表面Avidin结合的Ru-bpy-biotin量减少,在光照射下光电流信号降低。这一竞争性光电检测方法检测Biotin时,检出限为8μg/L。本方法可进一步扩展,应用于有机化合物的竞争性免疫检测。 相似文献