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One influential parameter which mediates interactions between many types of molecules and biological membranes stems from
the lumped contributions of the transmembrane potential, dipole potential and the difference in the surface potentials on
both sides of a membrane. With relevance to cell physiology, such electrical features of a biomembrane are prone to undergoing
changes as a result of interactions with the aqueous surrounding. Among the most useful tools devoted to exploring changes
of electrical parameters of a lipid membrane induced by certain extracellular ions, lipid composition, and embedded membrane
peptides and proteins, are spectroscopic imaging and the inner field compensation (IFC) method. In this work we layout the
principles of a fully computerized version of the IFC method, which makes it more readily available to users. As a direct
application, we deployed this improved version of the IFC method to time-resolve changes induced by alamethicin monomers upon
membrane dipole potential, following their aggregation within an artificial lipid membrane. Intriguingly, even prior crossing
the membrane core, the membrane-bound alamethicin monomers are shown to significantly increase the dipole potential of the
monolayer they reside in. Such data further emphasize the yet less-explored interplay between membrane-based protein and peptides,
and the membrane dipole potential. 相似文献
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Physical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to
both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface.
As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended
to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants
no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface
under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential
difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions
of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental
results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting
relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic
solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium
and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of
glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient
analitycal sensing device for quantitative determination in the field. 相似文献
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制备了甘氨酸-壳聚糖复合膜修饰玻碳电极(Gly-CTS/GCE),研究了抗坏血酸(AA)和尿酸(UA)在该修饰电极上的电化学行为。结果表明在pH=5.59的磷酸盐缓冲溶液中,AA、UA在Gly-CTS/GCE上均产生灵敏的不可逆氧化峰,其峰电流与浓度在一定范围内呈良好的线性关系。对AA和UA混合溶液平行测定7次,相对标准偏差分别为4.6%、2.9%,表明该电极重现性和稳定性良好。AA、UA在Gly-CTS/GCE电极上的氧化峰峰电位相差340mV,据此可实现对二者的同时检测,并可应用于实际样品测定。 相似文献
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Cholesterol is an important constituent of eukaryotic cell membranes, whose interaction with phospholipids leads to a broad
range of biological roles, such as: maintenance of proper fluidity, formation of raft domains, reduction of passive permeability
of various chemical species through the bilayer (e.g., glucose, glycerol, K+, Na+ and Cl− ions), and increased mechanical strength of the membrane. In this work we studied an interesting paradigm, as to whether
cholesterol-containing phosphatidylcholine biomembranes influence the kinetics and transport features of alamethicin oligomers
embedded into it. We demonstrate that moderate relative amounts of cholesterol increase the electrical conductance of various
sub-conductance states of the alamethicin oligomer, caused probably by a non-monotonic change in the lumped dipole moment
of the biomembrane. Our data suggest that biomembrane stiffness caused by cholesterol, visibly modifies the association-dissociation
rates of alamethicin oligomerization in the biomembrane. Moreover, increasing concentrations of cholesterol seem to lead to
more stable intermediate alamethicin oligomers. We show that in the presence of cholesterol, as the diameter of the alamethicin
oligomer increases, so does the time of another monomer to get picked up. These results brings into focus the interesting
issue of how oligomerization of proteins affects their interaction affinities for membrane-based lipids. 相似文献
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In this study we present novel evidence that strengthens the paradigm of selective transfer of energy mediated by a random gating of ion channels. Specifically, we investigated the spectral response of a noisy artificial biomembrane whose electrical properties were largely dictated by embedded alamethicin oligomers. In this respect, we first evaluated experimentally the linear transfer function of the system via the white-noise analysis method. We prove that such a system displays specific ranges of frequency over which input signals pass preferentially, depending on their spectral content and the holding potential across the artificial bilayer which contains alamethicin. By employing voltage-driven periodic stimulation of alamethicin oligomers, we demonstrate that overall response of the system obeys qualitatively the predictions inferred from the transfer function analysis of it. These results emphasize the exquisite ability of excitable membranes to behave as band-limited filters and allow for maximal transfer of energy from an external stimulus over well-defined frequency ranges. 相似文献
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C70X2(X=H,F, Cl)的稳定性和电子光谱 总被引:1,自引:0,他引:1
用INDO方法研究C70H2四种异构体的稳定性, 表明其最稳定异构体为1, 9-C70H2和7, 8-C70H2, 两者能量差为16.3KJ.mol^-^1, 与实验值及ab initio计算值接近; 光谱计算表明, 其特征吸收峰与实验值一致。在此基础上预测C70F2和C70Cl2的稳定性和电子光谱, 表明C70F2四种异构体的稳定性顺序与C70H2一致, 而C70Cl2则以21, 42-异构体最为稳定。二者的电子光谱与C70H2极其相似只是在500nm以上有细微差别。 相似文献
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