Evaluation of the thermal coefficient of the resistance to fluorophore rotation in model membranes

Scarlata, Suzanne

doi:10.1016/s0006-3495(89)82917-0

Cited by 10 publications

(13 citation statements)

References 21 publications

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“…25:7484-7488). The bilayer compressibility decreased with temperature and this decrease was similar with membrane depth consistent with the isotropic thermal expansion of membranes previously observed (Scarlata, S. 1989. Biophys.…”

supporting

confidence: 89%

“…Additionally, the emission spectra of several of the samples were checked and showed no changes under pressure. The limiting anisotropies used _10o Y°o here were from previous measurements (Scarlata, 1989): 0.312 for 2-, 6-, 9-, and 12-AS and 0.322 for 11-AU, and 16-AP for 381 nm excitation, and 0.123 for all probes at 316 nm excitation.…”

Section: Methodsmentioning

confidence: 99%

“…To gain insight into the changes in orientation that membrane components may undergo with pressure, we will measure the compressibility of different regions of the bilayer. Previously, we have found that the thermal expansion of dioleoylphosphatidylcholine (DOPC) bilayers is isotropic (Scarlata, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Compression of lipid membranes as observed at varying membrane positions

Scarlata

1991

Biophysical Journal

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We have measured the microscopic isothermal compressibility of dioleoyl- and dimyristyl-phosphatidylcholine multilayers and bilayers as a function of membrane depth by the pressure dependence of the polarization of a series of anthroyloxy fatty acids. In both systems, within experimental error, the compressibility did not change with membrane depth. The magnitudes of the compressibilities matched those of organic solids and those reported for dipalmitoylphosphatidylcholine multilayers from neutron diffraction measurements (Braganza, L. F., and D. L. Worcester. 1986. Biochemistry, 25:7484-7488). The bilayer compressibility decreased with temperature and this decrease was similar with membrane depth consistent with the isotropic thermal expansion of membranes previously observed (Scarlata, S. 1989. Biophys. J. 55:1215-1223). The vertical compressibility in the z direction is much lower than the horizontal (xy planes) for probes that lie parallel to the hydrocarbon chains which is consistent with an increase in bilayer thickness. The compressibility for probes that lie perpendicular to the hydrocarbon chains is more isotropic due to their limited spatial access to the z plane.

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supporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

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Compression of lipid membranes as observed at varying membrane positions

Scarlata

1991

Biophysical Journal

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“…We measured the change in anisotropy and average lifetime as a function of temperature and analyzed the data using eq 4 (see Materials and Methods), which yields the parameter b, the thermal coefficient of the viscosity which can be regarded as a thermal expansion coefficient (Scarlata, 1989). We find that from 12 to 37 °C GLUT-1 displays two b values with a transition at ~23 °C whether ligand is present or not (data not shown).…”

Section: Resultsmentioning

confidence: 99%

Effect of lipid packing on the conformational states of purified GLUT-1 hexose transporter

Scarlata

McBath²,

Haspel³

1995

Biochemistry

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The purpose of this study was to determine the effect of increased lipid packing on the conformational states of the GLUT-1 hexose transporter purified in endogenous lipids. The binding of glucose results in a conformational change that can be followed by a decrease in fluorescence intensity. Lipid packing was increased by subjecting the samples to hydrostatic pressure. We have found that in the absence of ligand, the fluorescence intensity decreased approximately 20% in the 600 bar range studied. In the presence of either saturating or half-saturating amounts of D-glucose, a substantial loss in intensity (approximately 80%) was observed. Similar decreases were also seen the presence of a glucose analog, maltose, or a noncompetitive inhibitor, cytochalasin B. Changes in the accessibility of aqueous soluble quenchers (I- and acrylamide) to GLUT-1 Trp and Tyr residues suggested that ligand binding causes interfacial fluorophores to move closer to ionic groups in the lipid head group region of the membrane. This idea was substantiated by (1) increased static quenching of the GLUT-1 fluorophores in the presence of ligand, (2) increased energy transfer efficiency between GLUT-1 fluorophores and a fluorescent membrane probe located close to the head group region, and (3) reduced change in rotational motion with temperature in the presence of ligand. Since the application of pressure results in an increase in bilayer thickness, and ligand binding causes a population of fluorophores to move closer to the membrane surface, then these interfacial interactions can be more stabilized under pressure. Studies monitoring the change in quenching of membrane probes by GLUT-1 tryptophans and energy transfer of GLUT-1 tryptophans to membrane probes support this idea.

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“…Temperature Dependence of in Liquid-Crystalline-and Gel-Phase Bilayers. £" is 2-fold larger for liquid-crystallineversus gel-phase bilayers of DMPC (Scarlata, 1989); i.e., the bilayer is more compressible in the liquid versus the gel state.…”

Section: Theorymentioning

confidence: 99%

Are membrane enzymes regulated by the viscosity of the membrane environment

Zakim

Kavecansky²,

Scarlata³

1992

Biochemistry

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We have examined the idea that membrane enzymes are regulated by the viscosity of surrounding lipids using data compiled from the literature for the effect of the change in membrane viscosity ([symbol: see text]) at the gel- to liquid-crystal-phase transition on the activities of several enzymes. The analysis was not extended explicitly to the problem of viscosity-dependent regulation of membrane enzymes in liquid-crystalline lipids because of the absence of exact data for values of [symbol: see text] in liquid-crystalline phases of variable composition. For most membrane enzymes studied, energies of activation are discontinuous, while kcat is continuous, at the main-phase transition. We consider that the energy of activation contains terms related to the height of the chemical barrier to reaction and terms due to the mechanical properties of the bilayer, such as the work of expansion during the catalytic cycle and the temperature dependence of [symbol: see text]. We find that the differences in energies of activation, above and below the break points in Arrhenius plots, are orders of magnitude larger than can be accounted for by the above mechanical factors. Thus, discontinuities in energies of activation at the phase transition appear to reflect changes in the chemical barrier to reaction, which is independent of [symbol: see text]. The theorectical analysis indicates too that values of [symbol: see text] for bilayers in the liquid-crystalline phase would have to be several orders of magnitude larger than those for gel phases in order to provide a basis for viscosity-dependent regulation of membrane enzymes in liquid-crystalline phases.(ABSTRACT TRUNCATED AT 250 WORDS)

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Evaluation of the thermal coefficient of the resistance to fluorophore rotation in model membranes

Cited by 10 publications

References 21 publications

Compression of lipid membranes as observed at varying membrane positions

Compression of lipid membranes as observed at varying membrane positions

Effect of lipid packing on the conformational states of purified GLUT-1 hexose transporter

Are membrane enzymes regulated by the viscosity of the membrane environment

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