Protein electric response signals from dielectrically polarized systems

Keszthelyi, L.; Ormos, Pál

doi:10.1007/bf01870276

Cited by 42 publications

(41 citation statements)

References 35 publications

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“…It is well documented that the electric signal of light-excited WTbR starts with a fast negative signal, followed by longer-living positive components [15]. The saturating time integral of the electric response (Fig.…”

Section: Wild-type Bacteriorhodopsinmentioning

confidence: 82%

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Photoexcitation of the O intermediate of bacteriorhodopsin and its mutant E204Q

Tóth-Boconádi¹

2001

JBPC

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Photoexcitation of the intermediates of the bacteriorhodopsin photocycle provides valuable information on their particular rôles. Photoelectric responses from the K, M and N forms are available but the electric response of the excited O intermediate is poorly known. Double flash experiments with varying time delays between the flashes have been carried out, revealing that the photoreactions of the O intermediates in wild-type bacteriorhodopsin and in mutant E204Q are quite different. The photoreaction of the O intermediate of the wild-type bacteriorhodopsin is more-or-less similar to that of the bR-state, i.e. it translocates charge, whereas in the mutant E204Q the photoreaction is merely a small disturbance involving minor internal charge motions.

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Section: Wild-type Bacteriorhodopsinmentioning

confidence: 82%

“…The components have their counterparts in absorption [15]. These properties are used as references for discussing the electric responses of the excited O intermediates.…”

Section: Discussionmentioning

confidence: 99%

Photoexcitation of the O intermediate of bacteriorhodopsin and its mutant E204Q

Tóth-Boconádi¹

2001

JBPC

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“…Note that the undefined proportionality constant in Eq. 1 depends on the ionic relaxation around the pm (15). Because of the membrane anisotropy and other reasons discussed in ref.…”

Section: T) (B) Iy(t) (C) Iz(t)mentioning

confidence: 99%

“…When the orientation is ''frozen'' in a gel, the system remains stable and, in contrast to suspensions, it enables long, repetitive data acquisition in the absence of an external orienting electric field (14). Because the sample is well defined and a quantitative analysis of the photoelectric signal is possible, one can determine the charge displacements during each step of the photocycle (15). This technique has the important advantage that spectroscopic changes can be recorded on the same sample.…”

mentioning

confidence: 99%

Interpretation of the spatial charge displacements in bacteriorhodopsin in terms of structural changes during the photocycle

Dér

Oroszi

Kulcsár

et al. 1999

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

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We have recently introduced a method, made possible by an improved orienting technique using a combination of electric and magnetic fields, that allows the threedimensional detection of the intramolecular charge displacements during the photocycle of bacteriorhodopsin. This method generates electric asymmetry, a prerequisite for the detection of electric signal on the macroscopic sample, in all three spatial dimensions. Purple membrane fragments containing bacteriorhodopsin were oriented so that their permanent electric dipole moment vectors were perpendicular to the membrane plane and pointed in the same direction. The resulting cylindrical symmetry was broken by photoselection, i. e., by f lash excitation with low intensity linearly polarized light. From the measured electric signals, the threedimensional motion of the electric charge center in the bacteriorhodopsin molecules was calculated for the first 400 s. Simultaneous absorption kinetic recording provided the time-dependent concentrations of the intermediates. Combining the two sets of data, we determined the discrete dipole moments of intermediates up to M. When compared with the results of current molecular dynamics calculations, the data provided a decisive experimental test for selecting the optimal theoretical model for the proton transport and should eventually lead to a full description of the mechanism of the bacteriorhodopsin proton pump.Bacteriorhodopsin (bR) is an integral protein in the plasma membrane of Halobacterium salinarum (1). Upon light absorption, bR transports protons across the membrane, converting the photon energy into the energy of a proton electrochemical gradient (for recent reviews, see refs. 2 and 3). bR is a single small protein and is the simplest known active ion pump and biological light energy transducer. Consequently, it is a prototype system for studying the basic steps and rules of biological energy transduction. bR consists of the 23-kDa protein moiety and a retinal chromophore attached to the side chain of Lys-216 via a protonated Schiff base. The retinal is located about halfway through the membrane and sustains an angle of Ϸ70°with the membrane normal. Trimers of bR form twodimensional crystalline patches in the plasma membrane. These purple membrane fragments (pm) can be isolated as sheets of about 0.5-m diameter.

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“…This charge motion generates, this way, an electrochemical gradient across the membrane, which could be recorded as an electric signal (Lanyi, 1999;Keszthelyi and Ormos, 1989;Mostafa, 1998). bR has several potential biotechnological applications (Oesterhelt et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Effect of β-particles on the retinal chromophore in bacteriorhodopsin of Halobacterium salinarium

Mostafa

2004

Radiation Measurements

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Protein electric response signals from dielectrically polarized systems

Cited by 42 publications

References 35 publications

Photoexcitation of the O intermediate of bacteriorhodopsin and its mutant E204Q

Photoexcitation of the O intermediate of bacteriorhodopsin and its mutant E204Q

Interpretation of the spatial charge displacements in bacteriorhodopsin in terms of structural changes during the photocycle

Effect of β-particles on the retinal chromophore in bacteriorhodopsin of Halobacterium salinarium

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