Postnatal expression of Hu-bcl-2 gene in Lurcher mutant mice fails to rescue Purkinje cells but protects inferior olivary neurons from target-related cell death

Two alternative mechanisms are frequently used to describe ionic permeation of lipid bilayers. In the first, ions partition into the hydrophobic phase and then diffuse across (the solubility-diffusion mechanism). The second mechanism assumes that ions traverse the bilayer through transient hydrophilic defects caused by thermal fluctuations (the pore mechanism). The theoretical predictions made by both models were tested for halide anions by measuring the permeability coefficients for chloride, bromide, and iodide as a function of bilayer thickness, ionic radius, and sign of charge. To vary the bilayer thickness systematically, liposomes were prepared from monounsaturated phosphatidylcholines (PC) with chain lengths between 16 and 24 carbon atoms. The fluorescent dye MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) served as an indicator for halide concentration inside the liposomes and was used to follow the kinetics of halide flux across the bilayer membranes. The observed permeability coefficients ranged from 10(-9) to 10(-7) cm/s and increased as the bilayer thickness was reduced. Bromide was found to permeate approximately six times faster than chloride through bilayers of identical thickness, and iodide permeated three to four times faster than bromide. The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores. Halide permeation therefore differs from that of a monovalent cation such as potassium, which has been accounted for by a combination of the two mechanisms depending on bilayer thickness.     

Electron capture gas chromatography of nanogram amounts of tertiary amines as trichloroethyl carbamates

The overall permeability of epithelial tissues to solutes is generally determined by analyzing net or unidirectional transepithelial fluxes in response to transepithelial differences of concentration and/or electrical potential using relations that describe diffusional movements across a single membrane. If the solute is uncharged and diffusional movements are transcellular, the overall transepithelial permeability coefficient is determined by the permeabilities of the two limiting cell membranes combinded in series. However, if the solute is charged and the pathway for transepithelial movement involves diffusional flows across at least two membranes arranged in series (i.e. transcellular transport), the value of the overall transepithelial permeability coefficient determined using relations that describe ionic diffusion across a single membrane is not an accurate measure of the permeabilities of the two limiting membranes combined in series. Further, if ionic diffusion is transcellular, permeability coefficients determined from studies of transepithelial fluxes are not only quantitatively incorrect but can also result in grossly erroneous interpretations of changes in transepithelial permeabilities and faulty inferences regarding the route of transepithelial ionic diffusion.     

A potentiostatic study of oxygen transmissibility and permeability through hydrogel membranes

The permeability characteristics of membranes prepared from hydrogels of poly(2-hydroxyethylmethacrylate) (PHEMA) and poly(2-hydroxyethylmethacrylate-co-N,N-dimethylacrylamide) (PHNDA) are described. True values of the permeability and transmissibility coefficients of oxygen in the membranes are determined by using electrochemical procedures involving the measurement of the steady state current either in membranes with different thickness or in a single membrane in which its thickness is varied with layers of moistened paper. Comparison of the results obtained for the transport properties in these hydrogels with others obtained in other hydrogels permit to conclude that the degree of swelling rather than the chemical nature of the hydrogels affects the permeation properties. The chemical structure presumably only affects in high degree the chemical stability and flexibility of the hydrogel membranes.     

氢气分离提纯用钯及钯合金膜的研究进展

伴随着煤、石油和天然气等传统化石能源在使用过程中产生的温室效应、能源危机等弊端,更清洁的氢能逐渐受到关注。氢能在能源、交通、工业等领域具有广阔的应用前景,尤其以燃料电池车为代表的交通领域是氢能初期应用的突破口与主要市场。而氢燃料电池对氢气浓度要求较高,氢气中即使微量的H2S和CO杂质也会严重降低电池性能。因此,需要对氢气进行分离纯化去除杂质气体。钯及钯合金膜由于对氢气具有极高的选择渗透性而应用于氢气的分离提纯,然而钯及钯合金膜的化学稳定性问题一直制约其广泛应用。本文介绍了纯Pd膜,Pd-Ag,Pd-Y,Pd-Pt,Pd-Cu和Pd-Au二元合金膜以及Pd-Ag-M,Pd-Cu-M三元合金膜氢渗透与抗杂质气体毒化方面的研究进展及存在问题。纯钯膜在低温下存在氢脆现象且易被杂质气体毒化;与纯钯膜相比,钯基二元合金膜成本较低,Pd-Ag,Pd-Y合金膜透氢性能较好而抗杂质气体毒化性能较差,Pd-Pt,Pd-Cu和Pd-Au合金膜则具有相反的特性;钯基三元合金膜在一定程度上提高了二元合金膜的透氢性能并改善了抗杂质气体毒化的性能,但仍存在合金元素偏析、各组元成分比例不易精确控制等问题,且钯基三元合金膜较之二元合金膜合成工艺更复杂、成本更高。最后,对钯合金膜未来的研究方向进行了展望。     

Effect of ultrasound on the permeability of D2O through cellulose membranes

The effect of ultrasound energy on the permeability of water through cellulose membranes was studied using deuterium oxide (D2O) as a tracer. The same membrane was used for control (no ultrasound) and ultrasound experiments in a sequential reversal design. Transfer of D2O to a 2% albumin solution was measured in a glass dializing cell with membrane area of 11 cm2. Ultrasonic energy was supplied for 45 min by a hydrosonic bath (Linden Laboratories) at an intensity of 0.18 watt/cm2, an energy level commonly used for therapeutic purposes. Statistical analysis showed a significant increase in water transfer due to the ultrasound treatment irrespective of the sequence of application of ultrasound. It was concluded that ultrasound energy increases water permeability through cellulose dializing membranes. Whether or not increased water permeability is the operating mechanism underlying the beneficial effects of ultrasonic bath therapy remains unanswered.     

Energetics of permeation of thin lipid membranes by ions

The energy of an ion in a thin hydrocarbon membrane relative to its energy in a bulk aqueous phase is considered in terms of the electrostatic and surface components that may be expected to be involved. Except when diffusion activation energies are large compared to partition free energies, the latter will control permeation rate and the state of an ion having the lowest partition energy will be critical for its permeability. This minimum is found when an ion is surrounded with a thin layer of water. All ions of the same charge will tend to be at their lowest state in a sphere of water of the same size. It is concluded, therefore, that all ions of a given charge will have about the same permeability in lipid membranes.     

Nonesterified fatty acids induce transmembrane monovalent cation flux: host-guest interactions as determinants of fatty acid-induced ion transport

Nonesterified fatty acids are key intermediates in cellular metabolism whose intracellular concentration is regulated by multiple anabolic, catabolic, and oxidative enzymatic cascades. Herein, we demonstrate that fatty acids induce transmembrane monovalent cation flux with an apparent rate constant kapp = 10(-)4 - 10(-)3 s-1. Fatty acid-induced cation efflux exploits the ionic association of the cation with the carboxylate anion of the fatty acid and the subsequent transmembrane flip-flop of the fatty acid-cation complex. Rates of fatty acid-induced transmembrane cation flux were dependent upon complex host-guest interactions between the fatty acid-cation complex and the phospholipid constituents which comprise the membrane bilayer including (1) the degree of unsaturation of the fatty acid guest and the regiospecificity and stereospecificity of its olefinic linkages; (2) the phospholipid subclass and individual molecular species which constitute the host membrane phospholipids; (3) impedance matching of host and guest hydrophobic characteristics; and (4) the cholesterol content of the membrane bilayer. Arrhenius analysis demonstrated that fatty acid-induced K+ efflux was facilitated largely by changes in the entropy of activation of ion translocation and not the energy of activation. Moreover, Arrhenius analysis demonstrated that the energy of activation of ion translocation was phospholipid subclass specific. For example, arachidonic acid-induced cation efflux in membranes comprised of 16:0-18:1 plasmenylcholine possessed an Ea = 5.3 +/- 0.4 kcal/mol, while that for 16:0-18:1 phosphatidylcholine was 7.2 +/- 0.5 kcal/mol. Electrophysiologic measurements of planar lipid membranes containing 10 mol % arachidonic acid as a substitutional impurity confirmed the ability of physiologically relevant amounts of fatty acid to induce ion translocation with a specific conductance of 2.6 +/- 0.3 microS/cm2. Collectively, these results demonstrate that fatty acids facilitate transmembrane cation flux by an ion carrier type mechanism and suggest that fatty acid-mediated ion transport contributes to the leakage current present in many cell types and thus potentially modulates cellular responsivity during signal transduction where the intracellular content of fatty acids changes dramatically.     

Synthetically modified cellulose (SMC): a cellulosic hemodialysis membrane with minimized complement activation

More dialysis treatments have been performed with cellulose based membranes than with any other material. As unmodified cellulose membranes activate the complement system, much effort has been directed toward the development of noncomplement activating cellulose membranes. One successful approach was the substitution of -OH groups in the cellobiose units of the cellulose molecule with tertiary amino groups, which resulted in a membrane called Hemophan. Synthetically modified cellulose (SMC) is a new hemodialysis membrane made by specific chemical modification whereby aromatic benzyl groups are covalently introduced into the cellulosic structure by ether bonds, creating hydrophobic domains within the overall hydrophilic cellulose surface: basic research investigations have shown that a characteristic hydrophobic-hydrophilic balance of surfaces is a prerequisite for improved hemocompatibility. Several cellulose modifications with aliphatic and aromatic groups were performed to achieve a membrane with the desired hemocompatibility profile; SMC, having hydrophobic benzyl groups, causes minimal activation of blood complement, coagulation, and cell activation systems. In vitro experiments with blood showed that C5a generation for SMC was reduced by 94% relative to Cuprophan (compared with 96% for polysulphone, a synthetic hemodialysis membrane). Activation of coagulation (formation of the thrombin-antithrombin III complex [TAT]) in a clinical study showed that SMC caused 16 ng/ml TAT generation compared with 36 ng/ml for polysulphone. SMC, a low-flux cellulosic dialysis membrane, thus combines the typically high diffusive performance characteristics of cellulosic membranes with excellent hemocompatibility, matching synthetic dialysis membranes.     

Localization of a brain protein metabolically linked with behavioral plasticity in the goldfish

Isotonic suspensions of human erythrocytes were exposed to single electric pulses of intensity at a few kV/cm and duration in microseconds. Upon pulsation, the cell membranes became permeable to Na+ and K+, and the erythrocytes eventually hemolysed through the colloid osmotic effect of hemoglobin. The enhanced permeability is attributed to the formation of pores in the cell membranes. These pores are formed within a fraction of a microsecond, once the transmembrane potential induced by the applied electric field reaches a critical value of 1.0 V. Increased field intensity and pulse duration, or pulsation at low ionic strengths all expand the pore size, leading to an accelerated hemolysis reaction. In contrast to this expansion process, the initial step of pore formatin is governed solely by the magnitude of the transmembrane potential: the critical value of the potential stays essentially constant in media of different ionic strengths, nor does it change appreciably with varying pulse duration. An abrupt increase in membrane permeability at a transmembrane potential adround 1 V has been observed in many cellular systems. It is suggested that a similar mechanism of pore formation may apply to these systems as well.     

Action of triterpene glycosides of the dammarane series and their aglycones on lipid membranes

The action of the dammarane triterpene glycosides Rb1 and Rg1 and their aglycones 20(S) protopanaxatriole and 20(S) protopanaxadiole from Korean ginseng on permeability of bilayer lipid membranes formed of monolayers was studied. RgI, protopanaxatriole and protopanaxadiole in concentrations of 3, 0.5 and 30 micrograms/ml respectively formed single ionic channels in the water phase on the membrane side containing cholesterol. The channel conductivity was 5 to 30 pSm in 1 M KCl. The ionic channels were more selective with respect to K+ as compared to Cl-. Rb1 was also able to increase the conductivity of the lipid membranes. However, no jumps in the current characteristics of the single channels were detected. All the substances in high concentrations on one side of the membrane independently of the cholesterol content induced fluctuation of the high amplitude current (from several tens of pSm to several hundreds of nSm).     

Anxiety and alcohol abuse in patients in treatment for depression

Oxygen transport in thylakoid membranes of spinach chloroplasts (Spinacia oleracea) has been studied by observing the collisions of molecular oxygen with spin labels, using line broadening electron paramagnetic resonance (EPR) spectroscopy. Stearic acid spin labels were used to probe the local oxygen diffusion-concentration product. The free radical moiety was located at various distances from the membrane surface, and collision rates were estimated from linewidths of the EPR spectra measured in the presence and absence of molecular oxygen. The profile of the local oxygen diffusion-concentration product across the membrane determined at 20 degrees C demonstrates that this product, at all membrane locations, is higher than the value measured in water. From the profile of the oxygen diffusion-concentration product, the membrane oxygen permeability coefficient has been estimated using the procedure developed earlier (W.K. Subczynski, J.S. Hyde, A. Kusumi, Proc. Natl. Acad. Sci. USA 86 (1989) 4474-4478). At 20 degrees C, the oxygen permeability coefficient for the lipid portion of the thylakoid membrane was found to be 39.5 cm s-1. This value is 20% higher than the oxygen permeability coefficient of a water layer of the same thickness as the thylakoid membrane. The high permeability coefficient implies that the oxygen concentration difference across the thylakoid membrane generated under the illumination of the leaf by saturating actinic light is negligible, smaller than 1 microM.     

In vivo evidence of enhanced guanylyl cyclase activation during the hyperdynamic circulation of acute liver failure

The different efficiencies of sucrose and trehalose in protecting isolated spinach (Spinacia oleracea L.) thylakoids against freeze-thaw damage is quantitatively related to their ability to reduce the solute loading of the vesicles during freezing. In the present paper we show that this effect is based on a reduction of the solute permeability of the membranes. Permeability was measured with 14C-labeled glucose at temperatures between 0 and 10 degrees C. Glucose permeability was reduced by both sucrose and trehalose, with trehalose effective at much lower concentrations than sucrose. An analysis of the temperature dependence of glucose permeability in the presence and absence of trehalose revealed that a 50% reduction in permeability resulted from a 10% increase in activation energy and a 30% decrease in activation entropy. Using the fluorescence probe 1,6-diphenyl-1,3,5-hexatriene (DPH), we found that the reduced permeability of the membranes in the presence of trehalose was unaccompanied by a reduction in lipid fluidity. This also excluded the possibility of a solute-induced liquid crystalline to gel phase transition. A reduced partitioning of the hydrophobicity-sensitive dye merocyanine 540 into thylakoids and into membranes containing 50% digalactosyldiacylglycerol in the presence of trehalose as compared to sucrose and glucose showed that the lipid headgroup region of these membranes became less accessible for solutes. No significant difference in merocyanine partitioning in the presence of trehalose as compared to sucrose or glucose was apparent when monogalactosyldiacylglycerol dispersions or phosphatidylcholine vesicles were investigated.     

Fabrication of a graded pore-sized porous FeAl intermetallic membrane

Micro-porous FeAl membranes were prepared directly onto a macro-porous FeAl support through brushing and reactive synthesis using Fe and Al elemental powders with different particle sizes. X-ray diffraction, scanning electron microscope and pore structure testing were used to study the phase composition, interfacial microstructure and pore structure of the resulting graded pore-sized FeAl membrane. The effects of membrane thickness on permeability and maximum pore size were also investigated. Results showed that a metallurgically strong joint is formed between the membrane and support and that no cracks and defects may be found on the interface due to the elemental reactions, penetrating of coated powders into the pores of the support and the match of the thermal expansion coefficients between membrane and support. Membrane permeability decreased from 84.2 to 38.5?m^3?m^?2?kPa^?1?h^?1 and the maximum pore size of about 2.5 μm showed a slight change as the membrane thickness increased from 135.5 to 299.1?μm.     

The membrane of giant molluscan neurons: electrophysiologic properties and the origin of the resting potential

The molluscan neuron, because of its large size and accessibility, has been an important model for studying the electrophysiology of nerve cells. This review catalogs data about specific molluscan neurons, but the greater importance of this material is in the broad picture of how a neuronal membrane maintains internal potential and is responsive to changes in the environment. Electrical properties of the membrane. The mechanisms which contribute to the resting potential in molluscan neurons can be separated into ionic and metabolic components. When the electrogenic sodium pump is eliminated experimentally, the ionic component of the potential follows the constant field equation quite closely. Many of the "constants" and "parameters" which characterize the membrane of molluscan neurons are actually variables which depend upon temperature, ionic environment, and membrane potential. The evaluation of the electrical parameters is complicated by extensive infoldings of the somatic membrane, and by large axons which drain current from the soma. Most molluscan neurons have a very high specific membrane resistance and a correspondingly low potassium permeability. Membrane capacitance is close to the 1 microF/cm2 value which characterizes biological membranes. The current-voltage relation of molluscan neurons may be complicated by inward-going rectification, but if that is inhibited the I-V curve follows the prediction of either the constant field equation or a simple electrical model. Factors which modify membrane behavior. The resting potential of molluscan neurons is very sensitive to changes in temperature and Ko, through a combination of effects upon the electrogenic sodium pump, inward-going rectification, and the membrane "parameters". Inward-going rectification depends upon a rectifying K conductance, and can be eliminated by cold or the removal of Ko. Strong or prolonged currents have time-dependent effects upon the membrane, and excessive polarization leads to a "high conductance state". The underlying (non-rectifying) K permeability of the membrane is relatively insensitive to temperature and ionic changes, whereas the Na permeability increases with warming. Membrane resistance varies with both temperature and ions (because the I-V curve is sensitive to these conditions) but membrane capacitance is relatively insensitive to external factors. Electrogenic sodium transport. Sodium transport is electrogenic in molluscan neurons. It can be stimulated by warm temperatures and an excess of substrate (e.g. high Nai); it can be inhibited by cold, by an absence of substrate (e.g. low Ko), or by pharmacologic agents such as cyanide or ouabain.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bile salt-membrane interactions and the physico-chemical mechanisms of bile salt toxicity

We present evidence that ursodeoxycholate prevents toxicity of more hydrophobic bile salts by inhibiting micellar solubilization of membrane lipids. Using both centrifugal ultrafiltration and gel filtration methods we studied leakage of inulin from vesicles composed of egg phosphatidylcholine and cholesterol. We observed that the addition of tauroursodeoxycholate to taurodeoxycholate reduced leakage of inulin from large unilamelar vesicles compared to that seen with taurodeoxycholate alone. This protective effect was observed only at high membrane cholesterol:phospholipid ratios (> or = 0.5). By gel filtration we found that fractional leakage of inulin from vesicles was identical to fractional phospholipid solubilization, indicating that release of inulin from vesicles results from membrane dissolution rather than from increased permeability of otherwise intact membranes. Addition of tauroursodeoxycholate to taurodeoxycholate was found to suppress the dissolution of phospholipid from cholesterol-rich vesicles. Bile salts were found to absorb to vesicles with an affinity proportional to their relative hydrophobicity, as estimated by reverse phase HPLC. Adsorption affinity decreased progressively with increasing membrane cholesterol content. Different bile salts displaced each other from membranes in proportion to their respective binding, affinities. Tauroursodeoxycholate, which absorbed to membranes with low affinity, displaced taurodeoxycholate from vesicles only weakly. Based on these findings we postulate that bile salts may damage the liver through solubilization of canalicular membrane lipids. Ursodeoxycholate may protect the liver by inhibiting dissolution of the cholesterol-rich canalicular membrane by more hydrophobic endogenous bile salts. Biliary secretion of vesicles rich in phosphatidylcholine may buffer the intermicellar concentration of bile acids at levels below those required to disrupt the cholesterol-rich canalicular membrane; thus biliary vesicle secretion may have evolved as a mechanism to protect the biliary epithelium from injury by luminal bile salts.     

NOM Accumulation at NF Membrane Surface: Impact of Chemistry and Shear

The effects of solution chemistry, surface shear, and composition of natural organic matter (NOM) were investigated for their impact on accumulation of foulant material at the surface of charged polymeric nanofiltration membranes. The source of NOM was the Suwannee River. A bench-scale, batch recycle system was used with 20 hollow fiber, nanofiltration membranes. Membrane flux decline and foulant accumulation increased at low pH and high ionic strength as a result of neutralization of charge, electric double layer compression, and the apparent shift in conformation of charged NOM macromolecules. The rate of NOM accumulation decreased with operating time, suggestive of an eventual steady state between adsorption and desorption. The effect of NOM composition on membrane fouling could not be discerned by a standard technique to isolate hydrophobic and hydrophilic NOM fractions, quite possibly because of the fractionation methodology's failure to recover a small but important fouling fraction or because of NOM interactions that are lost when individual fractions are separately tested. However, a greater percentage of the hydrophilic than hydrophobic fraction permeated the membrane, in agreement with prior observations by others. Increasing the cross flow velocity from 85 to 255 cm∕s reduced the extent of flux decline, presumably due to hydrodynamic disruption of cake layer formation.     

Papaverine-induced changes in physiological characters of Ehrlich ascites tumor cell membranes

Physiological characters of Ehrlich ascites tumor cell membranes were altered by papaverine. The agent induced changes in membrane potential as monitored by cyanine dye (diS-C3-(5)) technique. Papaverine also strongly inhibited increase in membrane permeability to K+ ion induced by lysolecithin. In addition, papaverine inhibited oxygen uptake of the tumor cells and oxidative phosphorylation of their mitochondria, and slightly increased membrane fluidity. The results suggest that papaverine maintains compartmentation of K+ ion, energy metabolism, and membrane fluidity by regulating intracellular mitochondrial metabolism of Ehrlich ascites tumor cells.     

Energetics of inclusion-induced bilayer deformations

The material properties of lipid bilayers can affect membrane protein function whenever conformational changes in the membrane-spanning proteins perturb the structure of the surrounding bilayer. This coupling between the protein and the bilayer arises from hydrophobic interactions between the protein and the bilayer. We analyze the free energy cost associated with a hydrophobic mismatch, i.e., a difference between the length of the protein's hydrophobic exterior surface and the average thickness of the bilayer's hydrophobic core, using a (liquid-crystal) elastic model of bilayer deformations. The free energy of the deformation is described as the sum of three contributions: compression-expansion, splay-distortion, and surface tension. When evaluating the interdependence among the energy components, one modulus renormalizes the other: e.g., a change in the compression-expansion modulus affects not only the compression-expansion energy but also the splay-distortion energy. The surface tension contribution always is negligible in thin solvent-free bilayers. When evaluating the energy per unit distance (away from the inclusion), the splay-distortion component dominates close to the bilayer/inclusion boundary, whereas the compression-expansion component is more prominent further away from the boundary. Despite this complexity, the bilayer deformation energy in many cases can be described by a linear spring formalism. The results show that, for a protein embedded in a membrane with an initial hydrophobic mismatch of only 1 A, an increase in hydrophobic mismatch to 1.3 A can increase the Boltzmann factor (the equilibrium distribution for protein conformation) 10-fold due to the elastic properties of the bilayer.     

Crystal structure of a calcium-phospholipid binding domain from cytosolic phospholipase A2

Cytosolic phospholipase A2 (cPLA2) is a calcium-sensitive 85-kDa enzyme that hydrolyzes arachidonic acid-containing membrane phospholipids to initiate the biosynthesis of eicosanoids and platelet-activating factor, potent inflammatory mediators. The calcium-dependent activation of the enzyme is mediated by an N-terminal C2 domain, which is responsible for calcium-dependent translocation of the enzyme to membranes and that enables the intact enzyme to hydrolyze membrane-resident substrates. The 2.4-A x-ray crystal structure of this C2 domain was solved by multiple isomorphous replacement and reveals a beta-sandwich with the same topology as the C2 domain from phosphoinositide-specific phospholipase C delta 1. Two clusters of exposed hydrophobic residues surround two adjacent calcium binding sites. This region, along with an adjoining strip of basic residues, appear to constitute the membrane binding motif. The structure provides a striking insight into the relative importance of hydrophobic and electrostatic components of membrane binding for cPLA2. Although hydrophobic interactions predominate for cPLA2, for other C2 domains such as in "conventional" protein kinase C and synaptotagmins, electrostatic forces prevail.     

Investigation of the structure of thylakoid membranes (spinach) by means of small-angle neutron scattering

This paper presents experimental data on the determination of the thickness of thylakoid membranes by small-angle neutron scattering. The thylakoids were isolated from spinach chloroplasts. The partial volume of proteins and lipids in the "washed" and "unwashed" membranes was estimated. It is shown that the thickness of thylakoid membranes, measured with this techniques depends on the way the membranes were separated. When isolated thylakoids by the standard method, the membrane thickness amounted to 75 A but if the extracted thylakoids were additionally washed with the isolation medium, the measured thickness was 50 A. In this case a significant decrease in the protein partial volume of the membrane was observed. The obtained results make it possible to explain numerous data on X-ray and small-angle neutron scattering by thylakoid membranes of different origins, proceeding from the assumption that all these membranes have a unified structure and consist of a stable core with a thickness of about 50 A, and layers of peripheral, weakly bound proteins with a thickness which may depends on the nature of the object under investigation and extracting conditions.