Surface charge of purple membranes measured by laser Doppler velocimetry

Packer, Lester; Arrio, B.; Johannin, Georges; Volfin, Pierre

doi:10.1016/0006-291x(84)90467-4

Cited by 26 publications

(14 citation statements)

References 12 publications

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“…They monitored the change in the apparent spectroscopic pK, of neutral red bound to the membrane compared to its normal intrinsic pK, in the bulk solution, 6.5. Also suggesting a low surface charge density, Packer et al (1984) estimated only about 0.5 negative charges per 1140 A', at pH 7.4 in 10 mM HEPES-Na+ buffer, from electrophoretic light scattering measurements. Similar to Ehrenberg and Meiri (1983), the surface charge density of the apomembrane and the purple membrane were approximately identical.…”

Section: Measurements Of the Surface Potential And Surface Charge Denmentioning

confidence: 94%

“…This was also observed by Duiiach et al (1986). Assuming similar surface charge densities for the normal and the bleached membranes (see below: Ehrenberg and Meiri, 1983;Packer et al, 1984), this result again requires association with the membrane beyond what can be accounted for by the surface potential and double-layer trapping. Additional evidence that specific types of cations have specific effects on purple membrane and its photochemistry are discussed below.…”

Section: Cation Bindingmentioning

confidence: 96%

Section: Measurements Of the Surface Potential And Surface Charge Denmentioning

confidence: 98%

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PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

Jonas

Koutalos

1990

Photochem & Photobiology

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Section: Measurements Of the Surface Potential And Surface Charge Denmentioning

confidence: 94%

Section: Cation Bindingmentioning

confidence: 96%

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PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

Jonas

Koutalos

1990

Photochem & Photobiology

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“…On the other hand, Chang et al (1986) from atomic absorption spectroscopy and Duniach et al (1986) from ESR observe that bleached deionized membranes bind fewer divalent cations and more weakly than do deionized membranes. Because PM does not change its surface potential upon bleaching (Ehrenberg and Meiri, 1983;Packer et al, 1984), these observations probably indicate that specific conformational interactions between surface residues and divalent cations are also present. Indeed, circular dichroism (Kimura et al, 1984) and thermal denaturation (Chang et al, 1986) data suggest that chelation by divalent cation induces protein conformational changes.…”

mentioning

confidence: 93%

High sensitivity electron diffraction analysis. A study of divalent cation binding to purple membrane

Mitra

Stroud

1990

Biophysical Journal

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A sensitive high-resolution electron diffraction assay for change in structure is described and harnessed to analyze the binding of divalent cations to the purple membrane (PM) of Halobacterium halobium. Low-dose electron diffraction patterns are subject to a matched filter algorithm (Spencer, S. A., and A. A. Kossiakoff. 1980. J. Appl. Crystallogr. 13:563-571). to extract accurate values of reflection intensities. This, coupled with a scheme to account for twinning and specimen tilt in the microscope, yields results that are sensitive enough to rapidly quantitate any structure change in PM brought about by site-directed mutagenesis to the level of less than two carbon atoms. Removal of tightly bound divalent cations (mainly Ca2+ and Mg2+) from PM causes a color change to blue and is accompanied by a severely altered photocycle of the protein bacteriohodopsin (bR), a light-driven proton pump. We characterize the structural changes that occur upon association of 3:1 divalent cation to PM, versus membranes rendered purple by addition of excess Na+. High resolution, low dose electron diffraction data obtained from glucose-embedded samples of Pb2+ and Na+ reconstituted PM preparations at room temperature identify several sites with total occupancy of 2.01 +/- 0.05 Pb2+ equivalents. The color transition as a function of ion concentration for Ca2+ or Mg2+ and Pb2+ are strictly comparable. A (Pb2(+)-Na+) PM Fourier difference map in projection was synthesized at 5 A using the averaged data from several nominally untilted patches corrected for twinning and specimen tilt. We find six major sites located on helices 7, 5, 4, 3, 2 (nomenclature of Engelman et al. 1980. Proc. Natl. Acad. Sci. USA. 77:2023-2027) in close association with bR. These partially occupied sites (0.55-0.24 Pb2+ equivalents) represent preferential sites of binding for divalent cations and complements our earlier result by x-ray diffraction (Katre et al. 1986. Biophys. J. 50:277-284).

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“…The effect of aggregation of the native PMs on their EPM was significant and further affected the evaluation of their surface charge, which could possibly explain the different values obtained in the literature [5,12]. This fact was expressed not only in their different electrophoretic mobility, but also in their tendency towards aggregation and stability of the aggregates.…”

Section: Resultsmentioning

confidence: 97%

Effects of gamma-irradiation on the electrokinetic properties of purple membranes

Doltchinkova¹,

Stoilova²,

Baldjiiska³

1998

Radiation and Environmental Biophysics

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The effect of gamma-irradiation (5, 10 and 15 Gy) on the kinetic surface charge of purple membranes (PM) was followed by means of particle microelectrophoresis. The changes in electrophoretic mobility (EPM) were examined at 2, 5 and 26 h, respectively, following irradiation of native PM, and at 2, 26, 50 h and 5 days following irradiation of delipidated PM. It was concluded that the high inhomogeneity of the suspension, even after sonication, largely affects the measured zeta-potential. The 15-Gy treatment significantly increased the net negative surface charge density at 5 and 26 h after irradiation of native PM. However, the opposite effect of approximately twofold reduction of EPM values was derived from simultaneous studies concerning their delipidated form. Low irradiation doses clearly induced an enhancement of negative surface charge density at 2 h post-exposure as well as the formation of unstable structures of delipidated PM. The changes in electrokinetic properties might reflect the specific aggregate formation in both native and delipidated PM. It was suggested that the effect observed of both types of PM was mainly a structural phenomenon possibly related to the modification of functionally active residues.

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Surface charge of purple membranes measured by laser Doppler velocimetry

Cited by 26 publications

References 12 publications

PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

PURPLE MEMBRANE: SURFACE CHARGE DENSITY and THE MULTIPLE EFFECT OF pH and CATIONS

High sensitivity electron diffraction analysis. A study of divalent cation binding to purple membrane

Effects of gamma-irradiation on the electrokinetic properties of purple membranes

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