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排序方式: 共有196条查询结果,搜索用时 15 毫秒
1.
V V Cherny M Paulitschke M V Simonova E Hessel V S Ermakov YuASokolov D Lerche V S Markin 《General physiology and biophysics》1989,8(1):23-37
The action of the antiviral drug rimantadine on the structure of bilayer lipid membranes (BLM) and RBC membranes was investigated. Structural changes in BLM were recorded by ionophore conductivity changes and by changes in the third harmonic of capacity current signal due to lateral compression of BLM in an electric field. It was shown that the adsorption of rimantadine on BLM results in an increase in ionophore mobility in bilayer membranes of dioleolyllecithin (DOL) and common lipids of bovine brain (CL) and in a decrease in those of azolectin (A). Relative changes in the third harmonic signal also depend on the membrane composition and have different signs. The results may be explained by the rimantadine action on the lipid bilayer structure: "rigidification" of A-membranes and "fluidization" of BLM from DOL and CL. Structural reorganization of RBC membranes as investigated by the ability of the cells to enter a micropipette (inner diameter greater than or equal to 3 microns) thereby undergoing deformation. It was shown that rimantadine influences RBC deformability due to drug induced inhomogenous mechanical membrane properties. Also, rimantadine accelerated the process of artificially induced aggregation of erythrocytes. The relation of the effects on artificial and biological membranes, and the structural changes in the lipid phase of membrane are discussed. 相似文献
2.
Mechanical properties of the red cell membrane skeleton: analysis of axisymmetric deformations 总被引:1,自引:0,他引:1
The mechanical properties of erythrocyte membrane composed of a membrane bilayer and membrane skeleton are considered. Two membrane models are described: the model of free boundaries (MFB) and the model of immobilized boundaries (MIB). In MFB, the skeleton is assumed to be attached to the bilayer at a finite number of points, whereas MIB allows the interaction of each spectrin filament with the bilayer along its whole length. For MFB an estimate was made of the mechanical strain generated in the membrane by sucking erythrocytes into a micropipette. The existence of the deformation threshold is demonstrated, below which no mechanical strain, except that of bending, appears in the membrane. Thus only deformations exceeding this threshold result in strain. The relationship between the applied tension and the height of erythrocyte "tongue" sucked into a micropipette was determined. The MIB characteristics correspond to the model of Evans: strains in the membrane are generated at any deformation, however small, i.e. the threshold is equal to zero. A basic feature of this model is quite a different distribution of the skeleton deformations in the membrane. A comparison of the theoretical models and experimental data demonstrated the possibility of either MFB or MIB occurring, depending on the characteristic measurement time. 相似文献
3.
A mechanism of formation of protein-free regions in the red cell membrane: the rupture of the membrane skeleton 总被引:3,自引:0,他引:3
The process of rupture and redistribution of the red cell membrane skeleton is analyzed theoretically. Following the emergence of the rupture the spectrin-actin network is redistributed on the cytoplasmic surface of the membrane bilayer. Due to the interaction of the membrane skeleton and integral proteins the redistribution of the spectrin-actin network leads to the release of purely lipid regions of the membrane. The scale of the protein redistribution caused by the rupture of the membrane skeleton and the size of the lipid domains produced depend on the shape of the membrane and the value of the electrical interaction of the membrane proteins. The lipid domains occurring as a result of the rupture and relaxation of the spectrinactin network can spontaneously increase or decrease its area. The criteria determining the conditions which result in the system's evolutions leading to the domain growth have been obtained. The character of the evolution is determined by the shape of the membrane region in which the rupture occurs as well as the relation between the effective linear tension of the rupture boundary and the modulus of elasticity of the spectrin-actin network. 相似文献
4.
Staphylococcal nuclease unfolds at acidic pHs and refolds at neutral pH. Previous kinetic analysis based on both the direct pH jump and the sequential pH jump, from a native condition (pH 7.0) to pHs beyond unfolding transition zones (pH 3.0 and pH 12), and vice versa, supports the mechanism, D3<-->D2<-->D1<-->N0, in which N0 is the native state and D's are the three substates of the denatured form [Chen, H.M., You, J.L., Markin, V.S., & Tsong, T.Y. (1990) J. Mol. Biol. 220, 771-778; Chen, H.M., Markin, V.S., & Tsong, T.Y. (1992) Biochemistry 31, 1483-1491]. Here we show that both the single- and the double-pH jump kinetics of folding and unfolding to the intermediate pHs (3.4-5.0, i.e., in the transition zone), in which both the native and the denatured states coexist, are not compatible with this simple sequential model. At 25 degrees C, log tau 1(-1) (for the D1<-->N0 step) and log tau 2(-1) (for the D2<-->D1 step) vs pH show a square root of-shaped dependence on the final pH, with minimal values (tau 1(-1) of 0.56 s-1 and tau 2(-1) of around pH 3.9. The third relaxation tau 3 (for the D3<-->D2 step, 35 s) was independent of pH in the range 3.4-8.5. The square root of-shaped dependence on pH of log tau 1(-1) and log tau 2(-1) cannot be reproduced by the above but can be accounted for if each of N0, D1, and D2 is composed of many microscopic states in rapid equilibrium.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
pH-induced folding/unfolding of staphylococcal nuclease: determination of kinetic parameters by the sequential-jump method. 总被引:4,自引:0,他引:4
On the basis of previous stopped-flow pH-jump experiments, we have proposed that the acid- and alkaline-induced folding/unfolding transition of staphylococcal nuclease, in the time range 2 ms to 300 s, follows the pathway N0 in equilibrium with D1 in equilibrium with D2 in equilibrium with D3, in which D1, D2, and D3 are three substates of the unfolded state and N0 is the native state. The stopped-flow "double-jump" technique has been employed to test this mechanism and to determine the rate constants which would not be accessible by the direct pH jump because of the lack of fluorescence signal, i.e., the rates for the conversion of D1 to D2 and of D2 to D3. In the forward jump, a protein solution kept at pH 7.0 was mixed with an acidic or alkaline solution to the final pH of 3.0 or 12.2, respectively. The mixed solution was kept for varying periods of time, called the delay time, tD. A second mixing (the back jump) was launched to bring the protein solution back to pH 7.0. The time course of the Trp-140 fluorescence signals recovered in the back jump was analyzed as a function of tD. Kinetics of the unfolding were found to be triphasic by the double-jump method, contrary to the monophasic kinetics observed by the direct pH jump. Complex kinetics of unfolding are expected with the proposed kinetic scheme.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
6.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
7.
V S Markin 《Biophysical journal》1981,36(1):1-19
The relations among membrane structure, mechanical properties, and cell shape have been investigated. The fluid mosaic membrane models used contains several components that move freely in the membrane plane. These components interact with each other and determine properties of the membrane such as curvature and elasticity. A free energy equation is postulated for such a multicomponent membrane and the condition of free energy minimum is used to obtain differential equations relating the distribution of membrane components and the local membrane curvature. The force that moves membrane components along the membrane in a variable curvature field is calculated. A change in the intramembrane interactions can bring about phase separation or particle clustering. This, in turn, may strongly affect the local curvature. The numerical solution of the set of equations for the two dimensional case allows determination of the cell shape and the component distribution along the membrane. The model has been applied to describe certain erythrocytes shape transformations. 相似文献
8.
9.
V. S. Markin V. S. Sokolov L. I. Boguslavsky L. S. Jaguzhinsky 《The Journal of membrane biology》1975,25(1):23-45
Summary The electric properties of the bilayer lecithin membranes have been studied in the presence of the antibiotic nigericin. When the antibiotic concentration is about 10–6
m the conductivity of the BLM is increased up to 10–7 ohm–1 cm–2. The potassium ion concentration gradient gives rise to a transmembrane potential of the order of 40 mV per 10-fold concentration gradient with the side of the higher potassium concentration negative. The transmembrane potential produced by the hydrogen ion concentration gradient is a function of the potassium ion concentration which is equal on both sides of the membrane. For low potassium ion concentrations the hydrogen potential has the expected polarity with the solution having higher concentration of protons negative. For potassium ion concentrations exceeding 0.03m the hydrogen potential has the reverse polarity. This unexpected result cannot be accounted for in terms of the available simple hypotheses about the charge transport mechanism for nigericin in BLM. In order to account for the experimental results obtained, a theoretical approach has been developed based on the assumption that charge is transported across the membrane by nigericin dimers. The theoretical predictions are in satisfactory agreement with the experimental results. The model also yields some predictions which may be verified in future experiments. 相似文献
10.
Alexander G. Volkov Chrystelle L. Vilfranc Veronica A. Murphy Colee M. Mitchell Maia I. Volkova Lawrence O’Neal Vladislav S. Markin 《Journal of plant physiology》2013
The electrical phenomena and morphing structures in the Venus flytrap have attracted researchers since the nineteenth century. We have observed that mechanical stimulation of trigger hairs on the lobes of the Venus flytrap induces electrotonic potentials in the lower leaf. Electrostimulation of electrical circuits in the Venus flytrap can induce electrotonic potentials propagating along the upper and lower leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear electrical response in plant tissues. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small electrotonic potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of the applied voltage. Electrical stimulation of the lower leaf induces electrical signals, which resemble action potentials, in the trap between the lobes and the midrib. The trap closes if the stimulating voltage is above the threshold level of 4.4 V. Electrical responses in the Venus flytrap were analyzed and reproduced in the discrete electrical circuit. The information gained from this study can be used to elucidate the coupling of intracellular and intercellular communications in the form of electrical signals within plants. 相似文献