The influence of surface charge on the kinetics of ion-translocation across biological membranes

Rate equations have been developed which describe the concentration dependence for ion-translocation across charged membranes for those cases in which the translocation process can be considered to be formally equivalent with an enzymic process of a Michaelis-Menten type. We have limited ourselves to those cases in which the ion-translocational step through the membrane is electroneutral. In addition it is assumed that the sites on the membrane involved in the ion-translocation process can not move through the membrane when these sites are not occupied by ions.It is shown that in general deviations from Michaelis-Menten kinetics may be expected. In case of monovalent ion-translocation across oppositely charged membranes apparent negative homotrope cooperative effects may occur, whereas for ion-translocation across equally charged membranes apparent positive homotrope cooperative effects may be found. When the bulk aqueous phase also contains polyvalent ions both types of effects may occur both in the case of ion-translocation across oppositely charged membranes as well as with ion-translocation across a membrane of which the sign of the surface charge is the same as that of the ion translocated.Under limited conditions, also apparent single Michaelis-Menten kinetics may be observed. In these cases, however, the apparent K_m generally is no linear function of the concentration of a competing ion. It is shown that even when an ion does not bind to the translocation sites the K_m is affected by increasing concentrations of this ion, a phenomenon which is not expected when the membrane is not charged. The effects of divalent ions, added to the bulk aqueous phase as 1-1-electrolytes, upon the K_m are discussed in connection with in literature reported effects of Ca⁺⁺ upon the rate of uptake of several monovalent ions into plant cells.     

Activation of Shaker Potassium Channels : III. An Activation Gating Model for Wild-Type and V2 Mutant Channels

A functional kinetic model is developed to describe the activation gating process of the Shaker potassium channel. The modeling in this paper is constrained by measurements described in the preceding two papers, including macroscopic ionic and gating currents and single channel ionic currents. These data were obtained from the normally activating wild-type channel as well as a mutant channel V2, in which the leucine at position 382 has been mutated to a valine. Different classes of models that incorporate Shaker''s symmetrical tetrameric structure are systematically examined. Many simple gating models are clearly inadequate, but a model that can account for all of the qualitative features of the data has the channel open after its four subunits undergo three transitions in sequence, and two final transitions that reflect the concerted action of the four subunits. In this model, which we call Scheme 3+2′, the channel can also close to several states that are not part of the activation path. Channel opening involves a large total charge movement (10.8 e₀), which is distributed among a large number of small steps each with rather small charge movements (between 0.6 and 1.05 e₀). The final two transitions are different from earlier steps by having slow backward rates. These steps confer a cooperative mechanism of channel opening at Shaker''s activation voltages. In the context of Scheme 3+2′, significant effects of the V2 mutation are limited to the backward rates of the final two transitions, implying that L382 plays an important role in the conformational stability of the final two states.     

Photooxidation of ferrocyanide and iodide ions and associated phosphorylation in NH2OH-treated chloroplasts

NH₂OH-treated, non-water oxidizing chloroplasts are shown to be capable of oxidizing ferrocyanide and I^? via Photosystem II at appreciable rates (? 200 μequiv/h per mg chlorophyll). Using methylviologen as electron acceptor, ferrocyanide oxidation can be measured as O₂ uptake, as ferricyanide formation, or as H⁺ consumption (2 Fe²⁺ + 2H⁺ + O₂ → 2 Fe³⁺ + H₂O₂). I^? oxidation can be measured as methylviologen-mediated O₂ uptake, or spectrophotometrically, using ferricyanide as electron acceptor. The oxidation product I₂ is re-reduced, as it is formed, by unknown reducing substances in the reaction system.The rate-saturating concentrations of these donors are very high: 30 mM with ferricyanide and 15 mM with I^?. Relatively lipophilic Photosystem II donors such as catechol, benzidine and p-aminophenol saturate the photooxidation rate at much lower concentrations (< 0.5 mM). It thus seems that the oxidation of hydrophilic reductants such as ferricyanide and I^? is limited by permeability barriers. Very likely the site of Photosystem II oxidation is embedded in the thylakoid membrane or is situated on the inner surface of the membrane.The efficiency of phosphorylation (P/e₂) is 0.5 to 0.6 with ferrocyanide and about 0.5 with I^?. In contrast the P/e₂ ratio is 1.0 to 1.2 when water, catechol, p-aminophenol or benzidine serves as electron donor. These differences imply that only one of two phosphorylation sites operate when ferrocyanide and I^? are oxidized. Ferrocyanide and I^? are also chemically distinct from other Photosystem II donors in that their oxidation does not involve proton release. It is suggested that the mechanism of energy conservation associated with Photosystem II may be only operative when the removal of electrons from the donor results in release of protons (i.e. with water, hydroquinones, phenylamines, etc.).     

Formation of nonquasineutral vortex plasma structures with a zero net current

A nonquasineutral vortex structure with a zero net current is described that arises as a result of electron drift in crossed magnetic and electric fields, the latter being produced by charge separation on a spatial scale of about the magnetic Debye radius r _B = |B|/(4πen _e ). In such a structure with a radius of r ～ r _B , the magnetic field is maintained by a drift current on the order of the electron Alfvén current J _Ae = m _e c ³/(2e) and can become as strong as B ? m _e c ²/(er). Estimates show that, in a plasma with a density of n _e = 10²¹?10²³ cm^?3 and with nonzero electron vorticity driven by high-power laser radiation on a time scale on the order of θ _pe ^?1 , magnetic fields with a strength of B ～ 10⁸?10⁹ G are generated on micron and submicron scales. The system with closed current that is considered in the present paper can also serve as a model of hot spots in the channel of a Z-pinch.     

Localization of magnetized electrons in current filaments as a fundamental cause of Coulomb explosion

Mechanisms for generating current filaments in a dense plasma under the action of focused laser pulses and in a Z-pinch configuration are discussed. The main properties of current filaments with a zero and nonzero electron vorticity Ω _e =B?(c/e)?×p _e that originate at magnetic fields in the range 4πn _e m _e c²?B²?4πn _i m _i c² are investigated under the conditions of Coulomb explosion at currents below the ion Alfvén current. A study is made of the equilibrium configurations of nonquasineutral current filaments in a purely longitudinal (B_z) and a purely azimuthal (B_θ) magnetic field and also in a more general case of a helical magnetic field, having two components, under conditions such that the charge separation occurs on a spatial scale on the order of the magnetic Debye radius r_B ? |B|/(4πen_e. It is shown that strong electric fields generated in the current filaments are comparable in magnitude to the atomic field and are capable of accelerating ions to energies of several tens of megaelectronvolts. The ion dynamics in strong electric fields of the filaments is calculated numerically and is shown to lead to the formation of collisionless shock waves on time scales on the order of several inverse ion plasma frequencies ω _pi ^?1 . The possible formation of current filaments on different spatiotemporal scales is considered.     

Reactions of iron-sulfur proteins with the aquated electron

The reaction of parsley 2Fe-2S ferredoxin in the normal oxidized state with e_aq^? generated by pulse radiolysis techniques has been studied at ～25°C, pH 7–8, I = 0.10 M (NaClO₄). Rate constants k_e (e_aq^? decay) and k_p (protein absorbance change) are the same, second-order rate constant 9.7 × 10⁹ M^?1 sec^?1. The reaction exhibits close to 100% efficiency. With 8Fe-8S ferredoxin from Clostridium pasteurianum under identical conditions it now appears that k_p (although sometimes significantly smaller) is equal to k_e. Varying efficiencies are also observed with this protein depending on the batch used. The reasons for such variable behavior are not fully understood. With oxidized and reduced forms of Chromatium v. high-potential iron-sulfur protein (HIPIP), k_e and k_p are essentially the same, but the highest efficiency observed is only ～50%. The prevailing pattern is therefore that rate constants k_e and k_p are generally in step for proteins having a single (or identical) active site(s). When the active site is buried as with HIPIP the efficiency of the reaction appears to decrease.     

Chemical and solvent effects on the interaction of tetraphenylborate with lipid bilayer membranes

Alkali metal salts of tetraphenylboron dissociate in aqueous solution to yield the hydrophobic anion, BPh₄^?, which is strongly adsorbed at the surfaces of lipid bilayer membranes. Upon application of a transmembrane voltage pulse these anions cross the membrane without appreciable desorption, thereby exhibiting a transient electrical conductance. The relaxation time of this transient is governed by the height of the central potential barrier which the anions must surmount in crossing the membrane. Because of discrete charge effects, the barrier height and hence the observed relaxation time increase markedly with increasing surface density of adsorbed BPh₄^?. Since adsorbed BPh₄^? are in partition equilibrium with the same species dissolved in the aqueous phase, measurement of the relaxation time for BPh₄^? membrane conductance can be used to assay the aqueous-phase concentration of the hydrophobic anion. In this way we have observed the precipitation of KBPh₄ in water, obtaining a solubility concentration product of 1.0·10^?7 mol²·dm^?6 for the precipitation reaction at 25°C. This result is larger by a factor of two than the most directly comparable published values from other sources. In additional experiments we have reduced the polarity of the aqueous phases bathing the membrane by adding varying amount of ethylene glycol to the water. Using the same conductance relaxation assay, we have determined that partitioning of BPh₄^? into the membrane/solution interfaces is lessened as the polarity of the bathing solutions is reduced. This result is attributed to a lowering of the chemical potential of the BPh₄^? in the less polar medium.     

Hydrophobic ion probe studies of membrane dipole potentials

Hydrophobic anions of dipicrylamine and of sodium tetraphenylborate have been employed as probes of interfacial dipole potential variations in lipid bilayer membranes. Systematic variation of dipole potentials has been achieved by introduction of compounds incorporating N⁺ and B^? charge centers. Distribution of hydrophilic and and hydrophobic groups relative to these charge centers has been shown to control the orientation in the membrane/solution interface of the electric dipole moment formed by these centers. Thus triphenyl-[4-trimethylphenylammonium] borate orients with the B^? center, surrounded by phenyl groups, embedded in the membrane, while the smaller methylated N⁺ center is directed toward the aqueous phases. This orientation has been confirmed using dipicrylamine probe ions. Results obtained in this system have been interpreted quantitatively using a previously developed model incorporating discrete charge effects. A second class of compounds, $\text{tri}\text{-n-}\text{alkylamine}$ borane (T_nAB) complexes having the generic formula (C_nH_{$\text{2n+1}$})₃N⁺B^?H₃, have also been synthesized for this study, using even-carbon alkyls ranging from ethyl to decyl. Molecular orientation of the complex is with the N⁺ center and its associated alkyl groups directed into the membranes, while the protonated B^? center is directed toward the aqueous phases, as confirmed by use of tetraphenylborate ions as probes.     

Glycine transport by hemolysed and restored pigeon red cells effects of a domnan-induced electrical potential on entry and exit kinetics

The influence of a Donnan effect on the transport of glycine by hemolysed and restored pigeon red cells was examined. The Donnan effect was produced by replacing Cl^? with 2,4-toluenedisulfonate or glutamate. The effects of the associated membrane potential and inside-outside pH difference on glycine entry and exit rates were examined. The effects of pH on entry and exit rates in the absence of a Donnan effect were also examined.In the absence of a Donnan effect, Na⁺-dependent glycine entry requires the protonated form of a group with a pK_app of 7.9 and the depronated form of another group with a pK_app of 6.8. Neither of these are required for exit but the deprotonated form of a group(s) with a pK_app of 6.2 is required. The pK 7.9 group and pK 6.2 group probably react with H⁺ at the inner face of the membrane and the pK 6.8 group probably reacts at the outer face.The V for glycine entry was determined for cells with their Cl^? largely replaced by toluenedisulfonate and without such replacement. Between pH 6.1 and 7, the ratio of the respective V values, V_T/V_Cl, was 1.5–1.7. V_T/V_Cl rose above pH 7 to near 4 at pH 8.3. At pH 6.9, with glutamate replacing cell Cl^?, the analogous ratio (V_Glu/V_Cl) was 1.7. The increase of V_T/V_Cl above pH 7 could be quantitatively accounted for by the increase in cell [H⁺]/medium [H⁺] caused by the Donnan effect together with the assumption that the pK 7.9 group reacts with H⁺ at the inner face of the membrane.When cell Cl^? was replaced by toluenedisulfonate or glutamate there was a drop in the term in the glycine K_m describing Na⁺ dependence of glycine entry. When cell Cl^? was replaced by toluenedisulfonate there was a rise in the Na⁺-independent term in the glycine entry K_m. By replacing varying amounts of cell Cl^? with either toluenedisulfonate or glutamate, plots were obtained of entry rates vs. the cell [Cl^?]/medium [Cl^?] ratio consistent with the assumption that the Donnan-induced membrane potential acts on a “moving” charge. Glycine exit was only slightly accelerated by trans-toluenedisulfonate. The ratio, exit rate into toluenedisulfonate medium/exit rate into Cl^? medium rose with decreasing pH. This rise could be accounted for by a Donnan-induced inside-outside pH difference which affects a pK_app 6.2 group reacting with internal H⁺.The observed influences of the Donnan effect on V(glycine entry), on both components of K_m(glycine entry), on the shape of the plot of glycine entry rate vs. the cell [Cl^?]/medium [Cl^?] ratio and on glycine exit all fit the assumptions that when the empty porter reorients, one unit of negative charge accompanies it “across” the membrane and that no other steps involve charge movement.The properties of the system seem inconsistent with a translational (“ferry boar”) mobile carrier.     

Enhanced efficacy of nitrifying biomass by modified PVA_SB entrapment technique

In this study, we developed a novel technique for preparing polyvinyl alcohol (PVA) hydrogel as an immobilizing matrix by the addition of sodium bicarbonate. This resulted in an increase in the specific surface area of PVA_sodium bicarbonate (PVA_SB) hydrogel beads to 65.23 m² g^?1 hydrogel beads, which was approximately 85 and 14 % higher than those of normal PVA and PVA_sodium alginate (PVA_SA) hydrogel beads, respectively. The D _e value of PVA_SB hydrogel beads was calculated as 7.49 × 10^?4 cm² s^?1, which was similar to the D _e of PVA_SA hydrogel beads but nearly 38 % higher than that of the normal PVA hydrogel beads. After immobilization with nitrifying biomass, the oxygen uptake rate and the ammonium oxidation rate of nitrifying biomass entrapped in PVA_SB hydrogel beads were determined to be 19.53 mg O₂ g MLVSS^?1 h^?1 and 10.59 mg N g MLVSS^?1 h^?1, which were 49 and 43 % higher than those of normal PVA hydrogel beads, respectively. Scanning electron microscopy observation of the PVA_SB hydrogel beads demonstrated relatively higher specific surface area and revealed loose microstructure that was considered to provide large spaces for microbial growth. This kind of structure was also considered beneficial for reducing mass transfer resistance and increasing pollutant uptake.     

Biogeochemical changes at the sediment–water interface during redox transitions in an acidic reservoir: exchange of protons,acidity and electron donors and acceptors

Redox transitions induced by seasonal changes in water column O₂ concentration can have important effects on solutes exchange across the sediment–water interface in systems polluted with acid mine drainage (AMD), thus influencing natural attenuation and bioremediation processes. The effect of such transitions was studied in a mesocosm experiment with water and sediment cores from an acidic reservoir (El Sancho, SW Spain). Rates of aerobic organic matter mineralization and oxidation of reduced inorganic compounds increased under oxic conditions (OX). Anaerobic process, like Fe(III) and sulfate reduction, also increased due to higher O₂ availability and penetration depth in the sediment, resulting in higher regeneration rates of their corresponding anaerobic e^? acceptors. The contribution of the different processes to oxygen uptake changed considerably over time. pH decreased due to the precipitation of schwertmannite and the release of H⁺ from the sediment, favouring the dissolution of Al-hydroxides and hydroxysulfates at the sediment surface. The increase in dissolved Al was the main contributor to water column acidity during OX. Changes in organic matter degradation rates and co-precipitation and dissolution of dissolved organic carbon and nitrogen with redox-sensitive Fe(III) compounds affected considerably C and N cycling at the sediment–water interface during redox transitions. The release of NO₂^? and NO₃^? during the hypoxic period could be attributed to ammonium oxidation coupled to ferric iron reduction (Feammox). Considering the multiple effects of redox transitions at the sediment–water interface is critical for the successful outcome of natural attenuation and bioremediation of AMD impacted aquatic environments.     

Activation of Shaker Potassium Channels : I. Characterization of Voltage-dependent Transitions

The conformational changes associated with activation gating in Shaker potassium channels are functionally characterized in patch-clamp recordings made from Xenopus laevis oocytes expressing Shaker channels with fast inactivation removed. Estimates of the forward and backward rates for transitions are obtained by fitting exponentials to macroscopic ionic and gating current relaxations at voltage extremes, where we assume that transitions are unidirectional. The assignment of different rates is facilitated by using voltage protocols that incorporate prepulses to preload channels into different distributions of states, yielding test currents that reflect different subsets of transitions. These data yield direct estimates of the rate constants and partial charges associated with three forward and three backward transitions, as well as estimates of the partial charges associated with other transitions. The partial charges correspond to an average charge movement of 0.5 e₀ during each transition in the activation process. This value implies that activation gating involves a large number of transitions to account for the total gating charge displacement of 13 e₀. The characterization of the gating transitions here forms the basis for constraining a detailed gating model to be described in a subsequent paper of this series.     

Asp563 of the horizontal helix of subunit NuoL is involved in proton translocation by the respiratory complex I

The NADH:ubiquinone oxidoreductase couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. It contains a 110 Å long helix running parallel to the membrane part of the complex. Deletion of the helix resulted in a reduced H⁺/e^? stoichiometry indicating its direct involvement in proton translocation. Here, we show that the mutation of the conserved amino acid D563^L, which is part of the horizontal helix of the Escherichia coli complex I, leads to a reduced H⁺/e^? stoichiometry. It is discussed that this residue is involved in transferring protons to the membranous proton translocation site.     

3,5-Di-tert-butyl-4-hydroxybenzylidenemalononitrile. Effects of pH on its binding to liposomes and evidence for formation of a ternary complex with valinomycin and potassium ion

1. The properties of 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF 6847) were studied chemically and spectroscopically. Two molecular species of SF6847 were identified: the undissociated form (SFH; ?₃₆₃, 10 mM^?1) and the dissociated form (SF^?; ?₄₅₄, 35 mM^?1). The pK_a value of the molecule was determined to be 6.9.2. On the basis of these properties the interactions of SF6847 with liposomes and valinomycin · K⁺ were studied. The partition constants of SFH (Kⁿ_p and SF^? (K^?_p) to liposomes were determined separately; Kⁿ_p was 56 mM^?1 and was independent of the pH of the medium, whereas K^?_p dependend greatly on the pH, being 1.2 mM^?1 at pH 7.0 and 2.9 mM^?1 at pH 8.0. Using these values, the partition constant of total SF6847 (K_p) was calculated and found to be essentially the same as that calculated from the kinetics of proton uptake. It was concluded that the amount of SF^? bound to liposomes is rate limiting for proton uptake.3. The effects of membrane potential on partition constants were studied. The K^?_p decreased greatly upon generation of a membrane potential negative inside the liposomes but increased upon generation of a membrane potential positive inside the liposomes.4. The interaction of SF6847 with valinomycin in aqueous solution and in liposomes was demonstrated only in the presence of potassium ion. Potassium ion could not be replaced by sodium ion. Evidence was obtained for the formation of the ternary complex valinomycin · K⁺ · SF^? in liposomes and in hexane. It was concluded that SF^? became more soluble in the liposomal membranes on formation of this ternary complex. All these results support our proposed mechanism for the proton uptake cycle (Yamaguchi, A. and Anraku, Y. (1978) Biochim. Biophys. Acta 501, 136–149).     

Boosting Oxygen Evolution Kinetics by Mn–N–C Motifs with Tunable Spin State for Highly Efficient Solar‐Driven Water Splitting

Solar‐driven water splitting is in urgent need for sustainable energy research, for which accelerating oxygen evolution kinetics along with charge migration is the key issue. Herein, Mn³⁺ within π‐conjugated carbon nitride (C₃N₄) in form of Mn–N–C motifs is coordinated. The spin state (e_g orbital filling) of Mn centers is regulated by controlling the bond strength of Mn–N. It is demonstrated that Mn serves as intrinsic oxygen evolution reaction (OER) site and the kinetics is dependent on its spin state with an optimized e_g occupancy of ≈0.95. Specifically, the governing role of e_g occupancy originates from the varied binding strength between Mn and OER intermediates. Benefiting from the rapid spin state‐mediated OER kinetics, as well as extended optical absorption (to 600 nm) and accelerated charge separation by intercalated metal‐to‐ligand state, Mn–C₃N₄ stoichiometrically splits pure water with H₂ production rate up to 695.1 µmol g^?1 h^?1 under simulated sunlight irradiation (AM1.5), and achieves an apparent quantum efficiency of 4.0% at 420 nm, superior to most solid‐state based photocatalysts to date. This work for the first time correlates photocatalytic redox kinetics with the spin state of active sites, and suggests a nexus between photocatalysis and spin theory.     

Nonlinear theory of large-amplitude stationary solitary waves in symmetric unmagnetized e − e + and C 60 − C 60 + plasmas

It is shown that large-amplitude stationary solitary electrostatic waves can exist in a symmetric plasma (e ^? e ⁺ or C ₆₀ ^? C ₆₀ ⁺ ), and the relevant parameter ranges (i.e., the range of the Mach numbers and the degree to which the plasma should be nonequilibrium) are determined. The basic requirement for the existence of such waves, specifically, that the symmetric plasma be in a nonequilibrium state, can easily be satisfied in low-density collisionless ideal plasmas under laboratory conditions.     

Electrostatically induced change of the conformational order of charged lipid membranes

Raman spectroscopy and X-ray diffraction are used to investigate the influence of surface charges on the structure of ionizable lipid membranes of dimyristoylmethylphosphatidic acid. The membrane surface charge density is regulated by varying the pH of the aqueous phase. Changes of the conformational order of the lipid chains are determined from the intensity of the CC stretch chain vibrations around 1100 cm^?1 in a lipid Raman spectrum. In going from an electrical neutral to a negatively charged membrane, the conformational order is reduced by 5% in the ordered and by 9% in the fluid membrane phase, corresponding to 0.6 and 0.8 CC bonds, respectively, which change from a trans to a gauche conformation. The electrostatically induced conformational change is mainly concentrated at the lipid chain ends as indicated by the spectral variations of the 890 cm^?1 CH₃ rocking band of the chain termini. The X-ray diffraction experiments show that increasing the surface charge density in the ordered membrane phase leads to a lateral expansion of the packing of the lipid polar groups, whereas the packing of the lipid chains in a plane perpendicular to the chain axes remains constant, indicating an increase of the tilt of the lipid chains from δ = 10° (pH 3) to δ = 27° (pH 9).     

Effect of surface potential on the intramembrane electrical field measured with carotenoid spectral shift in chromatophores from Rhodopseudomonas sphaeroides

Changes in the surface potential, the electrical potential difference between the membrane surface and the bulk aqueous phase were measured with the carotenoid spectral shift which indicates the change of electrical field in the membrane. Chromatophores were prepared from a non-sulfur purple bacterium, Rhodopseudomonas sphaeroides, in a low-salt buffer. Surface potential was changed by addition of salt or by pH jump as predicted by the Gouy-Chapman diffuse double layer theory.When a salt was added at neutral pH, the shift of carotenoid spectrum to shorter wavelength, corresponding to an increase in electrical potential at the outside surface, was observed. The salts of divalent cations (MgSO₄, MgCl₂, CaCl₂) were effective at concentrations lower than those of monovalent cation salts (NaCl, KCl, Na₂SO₄) by a factor of about 50. Among the salts of monoor divalent cation used, little ionic species-dependent difference was observed in the low-concentration range except that due to the valence of cations. The pH dependence of the salt-induced carotenoid change was explained in terms of the change in surface charge density, which was about 0 at pH 5–5.5 and had negative values at higher pH values. The dependence of the pH jump-induced absorbance change on the salt concentration was also consistent with the change in the charge density. The surface potential change by the salt addition, which was calibrated by H⁺ diffusion potential, was about 90 mV at the maximum. From the difference between the effective concentrations with salts of mono- and divalent cations at pH 7.8, the surface charge density of (?1.9 ± 0.5) · 10^?3 elementary charge per Ų, and the surface potential of about ?100 mV in the presence of about 0.1 mM divalent cation or 5 mM monovalent cation were calculated.     

The structural transitions of erythrocyte membranes induced by cyclic AMP

The generalized structural transitions of erythrocyte membranes induced by cyclic AMP were registered by ESR, fluorescence, freeze-fracture and circular dichroism methods. Two transitions different in nature wre revealed. One, which arises at10^?11-10^?10 M cyclic AMP, is cooperative and may be considered as a consequence of interaciton of cyclic AMP with a receptor. It was calculated that a structural rearrangement in one erythrocyte ghost is induced by three cyclic AMP molecules. As a result of it the membranes are “loosened”.The other transition arises at 10^?10-10^?8 M cyclic AMP and depends on the activity of the protein kinase system. This transition was shown to be non-cooperative and due to phosphorylation of membranous proteins. During this rearrangement the membranes are “stiffened”.Both transitions were demonstrated to related to the membrane integrity.