Detection of bacteriorhodopsin trimeric rotation at thermal phase transitions of purple membrane in suspension

Mostafa, Hamdy I.A.

doi:10.1016/j.bpc.2023.107074

Cited by 2 publications

(5 citation statements)

References 59 publications

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“…The observed anomaly may originate from the thermal phase transition of lipids of PM from the gel phase to the liquid crystalline phase. This lipid transition in native PM (but randomly oriented in suspension) has been reported recently 9 to occurr, as stated before, within the range of 18−20 °C. Inspired by extensive measurements carried out on bR reconstituted in lipid vesicles in the literature, 10−13 it is more likely that a likewise lipid phase transition would also occur in native PM, at least within the temperature range of lipid relevance.…”

Section: Departure From Uniaxial Symmetry Is Structural Disordering D...supporting

confidence: 85%

Section: Discussionmentioning

confidence: 94%

“…Indeed, a model was proposed to describe the influence of the thermal phase transition of lipids on the assembly state of bR reconstituted in liposomal systems, as indicated from circular dichroism spectra that evidenced a disassembly for bR at the lipid thermal transition. In addition, for bR reconstituted in lipid vesicles, it was reported that the gel-to-liquid crystalline phase transition of lipids induces disassembly in the bR crystal lattice. , It was suggested that this crystalline disordering occurring at the temperature of the lipid phase transition does point to the chromophore being buried in the protein of bR, as inferred from electronic absorption features. This bR disassembly, presumably occurring in the liquid crystalline phase of lipids, was found to result in perturbations in the chromophore’s environment, as inferred from 15 nm-blueshift of the visible absorption spectrum of bR in the late M-intermediate in studies concerned with the photochemical cycle of bR.…”

Section: Resultsmentioning

confidence: 99%

“…It is worthwhile to note that the PM surface charge asymmetry reflects such thermally induced structural changes in bR. Actually, these structural changes at the thermal transition of lipids in PM were reflected as sharp alterations in the DC conductivity, 9 which is known to be relevant to the surface charge asymmetry on PM (as shown in Figure 5 therein 9 ). In this regard, it is important to confer a biophysical context to the conclusion about the broken axial symmetry as manifested by orthogonal changes in electrical responses, which are sensitive to structural changes and lipid-mediated alterations occurring in bR.…”

Section: Departure From Uniaxial Symmetry Is Structural Disordering D...mentioning

confidence: 96%

“…The lipids of PM are crucial in maintaining the structure of the bR crystal lattice . In a recent study, the lipid transition in native PM (freely in suspension) has been reported to occur within the range of 18–20 °C. Investigation of direction-dependent physical properties is important in explaining the properties of the lipid phase transition of PM owing to its anisometric shape.…”

Section: Introductionmentioning

confidence: 99%

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Uniaxial Symmetry Breaking in Bacteriorhodopsin at the Thermal Phase Transition of Lipids of Purple Membranes

Mostafa

2024

J. Phys. Chem. B

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The article correlates between symmetry breaking and phase transition. An analogy, extending from physics to biology, is known to exist between these two topics. Bacteriorhodopsin (bR) as a paradigm of membrane proteins has been used as a case study in the present work. The bR, as the sole protein embedded in what is called a purple membrane (PM), has attracted widespread interest in bionanotechnological applications. The lipids of PM have a crucial role in maintaining the crystal lattice of bR inside PM. For this reason, the present work has been concerned with elucidating the thermal phase transition properties of the PM lipids in orthogonal directions. The results indicated that the axial symmetry of bR exhibits considerable changes occurring at the thermal phase transition of lipids. These changes are brought by an anomaly observed in the time course of orthogonal electric responses during the application of thermal fields on PM. The observed anomaly may bear on symmetry breaking in bR occurring at the phase transition of lipids based on such analogy found between symmetry breaking and phase transition. Lipid–protein interactions may underlie the broken axial symmetry of bR at such lipid thermal transition of PM. Accordingly, thermally perturbed axial symmetry of bR may be of biological relevance relying on the essence of the crystal lattice of bR. Most importantly, a question has to be raised in the present study: Can bR, as a helical protein with broken axial symmetry, affect the symmetry breaking of helical light? This may be of potential technical applications based on a recent discovery that bR breaks the symmetry of helical light.

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Section: Departure From Uniaxial Symmetry Is Structural Disordering D...supporting

confidence: 85%

Section: Discussionmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Departure From Uniaxial Symmetry Is Structural Disordering D...mentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Uniaxial Symmetry Breaking in Bacteriorhodopsin at the Thermal Phase Transition of Lipids of Purple Membranes

Mostafa

2024

J. Phys. Chem. B

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Boolean Logic Gate Operation in Bacteriorhodopsin of Purple Membrane Based on a Molten Globule‐like State

Mostafa

2024

ChemPhysChem

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Bacteriorhodopsin (bR) of purple membrane (PM) has increasing technical interests, particularly in photonic devices and bioelectronics. The present work has concerned with monitoring the temperature dependence of passive electric responses in‐plane and out‐of‐plane of the membranes. Based on thermal properties observed orthogonally here for PM, a high‐temperature intermediate of bR has been suggested to populate at around 60 °C, which may be ascribed to a molten globule‐like state. This intermediate has been found to be enclosed between two reversible thermal transitions for PM. Large‐scale turnover in the energy of activation, for these two thermal transitions, occurs steeply at such state at 60 °C, above which does bR reverse the sign of dielectric anisotropy (i.e. crossover) provided the operating frequency should be above the crossover frequency, at which the reversal occurs. No such crossover was found to occur below the crossover frequency, even above the crossover temperature (i.e. 60 °C). Likewise, no such crossover was found to occur below the crossover temperature, even above the crossover frequency. Relying on this reasoning, a logic gate operation may be declared implicating bR for bioelectronics and sense technological relevance. In addition, the results specify “dual frequency” as well as “dual temperature” characteristics to bacteriorhodopsin.

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Detection of bacteriorhodopsin trimeric rotation at thermal phase transitions of purple membrane in suspension

Cited by 2 publications

References 59 publications

Uniaxial Symmetry Breaking in Bacteriorhodopsin at the Thermal Phase Transition of Lipids of Purple Membranes

Uniaxial Symmetry Breaking in Bacteriorhodopsin at the Thermal Phase Transition of Lipids of Purple Membranes

Boolean Logic Gate Operation in Bacteriorhodopsin of Purple Membrane Based on a Molten Globule‐like State

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