Oriented purple-membrane films as a probe for studies of the mechanism of bacteriorhodopsin functioning. I. The vectorial character of the external electric-field effect on the dark state and the photocycle of bacteriorhodopsin

Kononenko, A.A.; Лукашев, Е. П.; Maximychev, Alexander V.; Chamorovsky, Sergey K.; Rubin, A. B.; Тимашев, С. Ф.; Chekulaeva, L. N.

doi:10.1016/0005-2728(86)90021-6

Cited by 40 publications

(15 citation statements)

References 23 publications

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“…The voltage dependence of the amplitude of the electroabsorption spectrum in oriented D85N films is quadratic, with a threshold (Fig. 3), as seen in previous measurements on oriented and unoriented wild-type films (7,8). At the highest applied voltages, the fractional absorption change at 600 nm is -25% and can be seen by eye.…”

supporting

confidence: 80%

“…This produced films of moderate optical quality. High-opticalquality, oriented samples, in which a majority of the patches were aligned with their cytoplasmic side facing the substrate, were deposited on the same type of slide by using the technique of electrophoretic sedimentation (4,7,8). Optically thick wild-type BR films made in this manner exhibited photovoltages of typically 11.5 V upon illumination by yellow light of intensity 0.15 W/cm2, indicating a high degree of orientation of the constituent membrane patches.…”

mentioning

confidence: 99%

“…Application of an external field to films ofwild-type BR induces spectroscopic changes that are unrelated to the protonation state of the Schiff base (7,8). However, there are several mutants and retinal-analogsubstituted variants of BR in which the Schiff-base proton is much more weakly bound, as indicated by pK values in the range 7 to 9 (9)(10)(11)(12).…”

mentioning

confidence: 99%

“…This produced films of moderate optical quality. High-opticalquality, oriented samples, in which a majority of the patches were aligned with their cytoplasmic side facing the substrate, were deposited on the same type of slide by using the technique of electrophoretic sedimentation (4,7,8 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C.…”

mentioning

confidence: 99%

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Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin.

Kolodner¹,

Лукашев²,

Ching³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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The application of an external electric field to dry films of Asp-85 --Asn mutant bacteriorhodopsin causes deprotonation of the Schiff base, resulting in a shift of the optical absorption maximum from 600 nm to 400 nm. This is in marked contrast to the case of wild-type bacteriorhodopsin films, in which electric fields produce a red-shifted product whose optical properties are similar to those of the acid-blue form of the protein. This difference is due to the much weaker binding of the Schiff-base proton in the mutant protein, as indicated by its low pK of -9, as compared with the value pK 13 in the wild type. Other bacteriorhodopsins with lowered Schiff-base pK values should also exhibit a fieldinduced shift in the protonation equilibrium ofthe Schiffbase. We propose mechanisms to account for these observations. mutant bacteria with the Asp-85 --Asn (D85N) mutation (10),we have discovered that external electric fields cause reversible spectroscopic changes which unambiguously represent Schiffbase deprotonation. Explaining the mechanism of this deprotonation will require the application of recently developed numerical techniques of minimization of the electrostatic energy of the protein and may impose new constraints on its structure (13). In addition, this observation may have great technological significance: it may be possible to exploit the effect, using genetic and/or chemical modification of BR, to produce unique electrochromic materials-"electronic ink"-with important applications in the technology of reflective displays.Bacteriorhodopsin (BR) is a protein found in the cell membrane of the bacterium Halobacterium salinarium. BR consists of seven a-helices which span the membrane, forming a channel through which protons can be transported. Upon absorption of a photon, BR undergoes a photocycle which results in the translocation of a proton across the membrane, converting the free energy of the photon into chemical energy for metabolism (1, 2). BR can be isolated from the bacterium in the form of purple membranes (3)-so called because of a strong absorption band centered at 570 nm-in which trimers of BR molecules are incorporated in patches of lipid bilayer. These patches can be assembled into dry films for experimentation (4). The deep purple color of BR comes from the chromophore retinal, which is bound to a lysine residue inside the membrane channel via a protonated Schiff-base linkage. Unbound retinal in solution is faintly yellow, exhibiting a strong absorption centered at 360 nm. However, upon incorporation into BR, the retinal absorption band center shifts to 570 nm. This opsin shift is caused in large part by charge redistribution in the retinal due to the positive charge of the proton at the Schiff base. Deprotonation of the Schiff base during the M intermediate state of the BR photocycle leads to a transient partial abolition of the opsin shift, switching the absorption maximum from 570 nm to 410 nm (1, 2). BR variants in which the lifetime of the deprotonated state is prolonged by chemic...

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supporting

confidence: 80%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…This produced films of moderate optical quality. High-opticalquality, oriented samples, in which a majority of the patches were aligned with their cytoplasmic side facing the substrate, were deposited on the same type of slide by using the technique of electrophoretic sedimentation (4,7,8 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C.…”

mentioning

confidence: 99%

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Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin.

Kolodner¹,

Лукашев²,

Ching³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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“…The bR is polyanion (purple membrane fragments of Halobacterium salinarium or Halobacterium halobium) [230] with a single-chain polypeptide folded into seven α-helices which contain a single covalently bound chromophore present in every helix [231][232][233]. Thus, the bR is wellknown transmembrane protein working as a proton pump creating a light-driven pH gradient between intracellular and extracellular parts of purple bacteria [234][235][236][237][238]. The bright ion channels embedded in a lipid bilayer (approximately 5 nm thick) control the selective passage of ions and their movements from one side of the cell to the other [239].…”

Section: Non-fluorescent Prodrugs/converted Into Fluorescent Active Dmentioning

confidence: 99%

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

Miksa¹

2016

Med chem (Los Angeles)

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This review highlights the role of fluorescent dyes as active "molecular photoswiches" focusing on the application in bioimaging and anticancer therapies in the field of therapeutic delivery. The author describes the development of prodrugs targeted to specific cell types and polymeric nanocarriers (capsules, micelles and silica nanoparticles) used as fluorescent probes which offer advantages in the integration of "smart" features of fluorescent dyes into synthetic materials. The incorporation of biologically responsive components that cleave upon changes in pH or light irradiation is fundamental to the successful design of such carriers with capabilities to load and release therapeutics specifically at a target site.

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Biophotoreceptor Arrays

Knopf

Wang

2010

Encyclopedia of Industrial Biotechnology

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Biophotoreceptor arrays are hybrid electronic devices that utilize spectrally sensitive neuronal cells and biomolecules as the primary photon‐detecting element in a distributed network of light sensors. The patterned microelectrode arrays that interface with the biological material are constructed from readily available silicon‐based circuitry or, more recently, electrodes imprinted on flexible polymer substrates. From an engineer's perspective, these biological materials present new design opportunities for developing imaging systems that more closely emulate the signal detection and information processing structures found in nature. Several important attributes of natural vision include highly sensitive light receptors based on molecular phototransduction, a nonregular distribution of sensing elements on the imaging surface, and nonplanar image formation in the eye. The primate retina is one illustrative example of how phototransduction and neuronal interactions can lead to efficient imaging of dynamic three‐dimensional environments. The extraction and deposition of nerve cells and molecular proteins on microelectrode array platforms provide researchers with a means to observe the behavior of these distributed sensing systems. Organic and flexible polymer electronics represent a new technology that permit the creation of nonrigid photoreceptor arrays which replicate the curved imaging surfaces of single aperture and apposition compound eyes. A simple motion detection system is presented as an illustration of how photosensitive biomaterials and flexible printed electronics provide an alternative paradigm for developing new types of imaging systems. An important area where biomedical researchers can exploit engineered biophotoreceptor arrays is the fabrication of biocompatible artificial retinas and prosthetic devices for patients with severe visual impairment.

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Oriented purple-membrane films as a probe for studies of the mechanism of bacteriorhodopsin functioning. I. The vectorial character of the external electric-field effect on the dark state and the photocycle of bacteriorhodopsin

Cited by 40 publications

References 23 publications

Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin.

Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin.

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

Biophotoreceptor Arrays

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