Orientation of membrane fragments by electric field

Keszthelyi, L.

doi:10.1016/0005-2736(80)90023-1

Cited by 124 publications

(72 citation statements)

References 15 publications

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“…This concept can easily explain the pH dependence of the sign of the scattering transients if we assume basic bending of the fragments. The basic bending hypothesis becomes quite natural if we realize that the surface charge distribution of the purple membranes is asymmetric [12,13] and this involves the energetically more stable bent shape of the membranes. (The outer side has more space for charges and counterions.)…”

Section: Discussionmentioning

confidence: 99%

“…Since the retinal chromophore is near perpendicular (-70 °) to the membrane normal [5,12,17], by exciting the sample using a ,-, polarized laser InP E; (7 2~ -1 30.…”

Section: Discussionmentioning

confidence: 99%

“…Since the cytoplasmic side of the purple membranes is less negative at pH values below 5 [12,13], the basic bending is the same as that of the purple membranes in the living cells. Due to their positive charges, the protons released by the bacteriorhodopsin molecules can only decrease the negative charge on the convex side.…”

Section: Discussionmentioning

confidence: 99%

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Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Czégé

1988

FEBS Letters

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A change in light scattering was detected during the photoeycle of the purple membrane. A systematic study of the pH, viscosity and photoseleetion dependence of scattering kinetics is given. From the experimental data it follows that purple membranes are bent, depending on the pH, and that the extent of bending changes during the photocycle is due to the functional protein. A theoretical treatment is also given. The model explains all the experimental data and, as an important consequence, calls attention to the fact that exact kinetic measurements cannot be performed without immobilizing the purple membranes.

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Section: Discussionmentioning

confidence: 99%

“…Since the retinal chromophore is near perpendicular (-70 °) to the membrane normal [5,12,17], by exciting the sample using a ,-, polarized laser InP E; (7 2~ -1 30.…”

Section: Discussionmentioning

confidence: 99%

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Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Czégé

1988

FEBS Letters

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“…In this initial study wild-type PM patches in distilled water at pH ∼ 6 were electrodeposited onto an ITO substrate by applying a potential difference of +5 V to the ITO substrate for 25 s [18]. The ITO areal resistance was ∼30 /square and was obtained from Delta Technologies Limited.…”

Section: Methodsmentioning

confidence: 99%

Humidity-dependent open-circuit photovoltage from a bacteriorhodopsin/indium tin oxide bioelectronic heterostructure

et al. 2003

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“…One major family of techniques involves incorporation of pm in an oriented fashion into liposomes (9) or attaching them to planar bimolecular lipid membranes (10,11) that separate two aqueous compartments. A different approach uses pm suspension, where the permanent electric dipole moment, parallel to the membrane normal, orients the pm in a dc electric field of moderate strength (12). If a suspension of oriented pm is excited by a laser flash, the intramolecular charge displacement can be measured as a displacement current by electrodes immersed in the electrolyte (13).…”

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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Orientation of membrane fragments by electric field

Cited by 124 publications

References 15 publications

Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Light scattering changes and protein distortion in the bacteriorhodopsin during the photocycle

Humidity-dependent open-circuit photovoltage from a bacteriorhodopsin/indium tin oxide bioelectronic heterostructure

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

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