Proton and multinuclear N.M.R. studies of cyclogentiotetraose peracetate-alkali cation complexation.

Complexation of alkali cation picrates with cyclogentiotetraose peracetate (CGD4Ac) have been studied by 1H-N.M.R. spectroscopy in acetone d6 and nitromethane d3. We determined the stability constants directly from the observed change of the chemical shifts of H-4 and H-6 pro S protons of CGD4Ac at constant ligand concentration with increasing amounts of alkali salt. The stability constants have also been determined by multinuclear n.m.r. spectroscopies, from the observed change of the chemical shifts of Lithium-7, Sodium-23, Potassium-39, Rubidium-87 and Cesium-133 at constant alkali salt concentration with increasing amount of CGD4Ac. The stabilities of the complexes varied in the order Cs+ greater than Rb+ greater than K+ greater than Na+ greater than Li+. The complexation of CGD4Ac with Cs+ induced conformational change, the gg conformer being predominant at the complexed state. In most cases the cationic exchanges between the free and complexed sites were rapid. However in the CsPic-CGD4Ac-Acetone system the exchange was slow enough to observe below 288 K two 133Cs+ resonances.     

Calcium-sensitive univalent cation channel formed by lysotriphosphoinositide in bilayer lipid membranes.

A calcium sensitive univalent cation channel could be formed by lysotriphosphoinositide on an artificial bilayer membrane made of oxidized cholesterol. The modified membrane was selectively permeable to univalent cations, but was only very sparingly permeable to anions or divalent cations. Selectivity sequence among group IA cations was Rb+ greater than Cs+ greater than Na+ greater than K+ greater than Li+. The conductance of the membrane was increased up to a value of about 10-2 ohm-1/cm2 with an increase in the concentration of univalent cation, and was drastically depressed by a relatively small increase in the concentration of calcium ion or other divalent cations. The sequence of depressing efficiency among divalent cations was Zn+ greater than Cd2+ greater than Ca2+ greater than Sr2+ greater than Mg2+.     

Size-dependent allosteric effects of monovalent cations on rabbit liver fructose-1,6-bisphosphatase.

Effects of monovalent cations on the neutral rabbit liver fructose-1,6-bisphosphatase are multifunctional and dependent on their nonhydrated ionic size. (a) The maximal velocity is increased by addition of monovalent cations with the optimum stimulation occurring with a nonhydrated ionic radius of 1.2 A in the presence of a chelating agent such as EDTA. (B) Activation curves are sigmoidal with n values varying from 1.5 to 2.3 as ionic radius of monovalent cation increases. The apparent Ka values from 16.0 to 180 mM, obtained for various monovalent cations, have a linear relationship to ionic radii of cations. (c) At lower concentrations of fructose 1,6-bisphosphate monovalent cations show the inhibitory effect and the apparent Km for fructose 1,6-bisphosphate is increased as the concentration of monovalent cation is increased. A linear relationship is obtained between the slopes of increase in the Km and the reciprocals of ionic volume of monovalent cations. (d) The apparent Ka for Mg2+ is also increased as the concentration of monovalent cation is increased, and a linear relationship is obtained again between the increases in Ka and the reciprocals of ionic volume of monovalent cations. The cooperative nature for Mg2+ saturation is decreased as the Ka increases. (e) The apparent Ki for AMP is also linearly altered as the concentration of monovalent cation is varied. However, the alteration of the Ki is unusual, that is, the smaller cations than K+ increase the Ki (Li+ greater than Na+ greater than NH4+), whereas the larger cations decrease the value ((CH2CH2OH)3N+ greater than Cs+ greater than Rb+). The effect of K+ is insignificant. Alterations in the Ki are also linearly related to the reciprocals of ionic volume of monovalent cations. The cooperative nature for AMP inhibition is decreased or increased as the Ki increased or decreased. (f) In the absence of the chelating agent, the curves for Mg2+ saturation and AMP inhibition were hyperbolic without monovalent cations. By addition of monovalent cation the Ka for Mg+2+ or Ki for AMP is increased and cooperative natures for binding of both ligands are induced. For nonspherical monovalent cations, the application of "functional ionic radius" is proposed. Functional ionic radii of NH4+, (CH2OH)3CNH3+, and (CH2CH2OH)3N+ are estimated to be 1.17, 2.55, and 2.87 A, respectively. The presence of two distinct sites for the actions of monovalent cations is suggested.     

Palytoxin induces an increase in the cation conductance of red cells

Palytoxin (PTX), isolated from the marine soft coral Palythoa tuberculosa, increases the cation conductance of human red cell membranes. In the presence of 10(-10) M PTX and 10(-5) M DIDS, the membrane potential approximates the equilibrium potential for Na+ or K+ rather than Cl-. Even in the absence of DIDS, the Na+ and K+ conductances were greater than the Cl- conductance. The selectivity of the PTX-induced cation conductance is K+ greater than Rb+ greater than Cs+ greater than Na+ greater than Li+ much greater than choline+ greater than TEA+ much greater than Mg2+. Measurements of K+ efflux revealed two apparent sites for activation by PTX, one with a Kal of 0.05 nM and a maximum flux, nu max1, of 1.4 mol/liter of cells per h and another with a Ka2 of 98 nM and a nu max2 of 24 mol/liter of cells per h. These effects of PTX are completely blocked by external ouabain (300 microM) and prevented by internal vanadate (100 microM). When the PTX channels are open, the Na,K pumps do not catalyze ATP hydrolysis. Upon thorough washout of cells exposed to about five molecules of PTX/pump, the Na,K pump of these cells operates normally. Blockage of the positively charged NH2 terminus of PTX with a p-bromobenzoyl group reduces the potency of the compound to induce Na and K fluxes by at least a factor of 100, and to compete with the binding of [3H]ouabain by at least a factor of 10. These data are consistent with the conclusion that PTX binds reversibly to the Na,K pumps in the red cell membrane and opens a (10-pS) channel equally permeable to Na and K at or near each pump site.     

Channel formation properties of black widow venom

Black widow venom in the concentration 1--10 mkg/ml added on one side of the bilayer of common bovine brain phospholipids induces the formation of conductivity channels with high cation-anion selectivity with the number of cation transfer for K+, Ca2+, Sr2+, Mg2+, Na+, Cs+, Li+ equaling 0.98, 0.97, 0.96, 0.94. 0.88. 0.82, 0.82 correspondingly (at pH = 7.5). At pH less than 3.5 the channels are slightly selective for anions (the number of cation transfer 0.4). Potential-dependence of the channels is found, which is explained by microstructural reconstruction of their protein complex.     

Vinyl polymers based on L-histidine residues. Part 2. Swelling and electric behavior of smart poly(ampholyte) hydrogels for biomedical applications

Hydrogels based on the uncharged N-isopropylacrylamide and the ionic ampholyte N-acryloyl-L-histidine showed a reversible multiple-responsive volume change and volume phase transition behavior in aqueous solution. The phase transition phenomenon was induced by the temperature, the pH, the salt-type concentration, and the electric potential. The kind of cation (Na+, K+, Cs+, Mg2+, Ca2+, Sr2+) and anion (Cl-, ClO4-, NO3-, SO4(2-)) strongly influenced the critical concentration that improved the phase separation of the gels. The volume of the collapsed gel can be hundred times smaller than that of the swollen one. The oscillatory swelling of the gels in response to temperature and pH (4 and 9) changes was fast and reversible, while the contractile behavior in the electric field showed response only at pH 9, i.e., when the amount of negative charges on the L-histidine residues predominated. The electrically induced anisotropic gel deswelling was attributed to the syneresis of water from the gel. The nontoxicity against the RAW264 cell line and the low osmotic pressure exhibited by the swollen gels make these compounds useful scaffolds for human organs. The ability to load and release an ionizable drug molecular model (ferulic acid) from the hydrogels was shown also at different pH values.     

Nonmonotonic trends in electrolyte-induced injury to rapidly cooled erythrocytes.

Rapid freeze-thaw injury to erythrocytes and erythrocyte ghosts has been shown to be strongly cation dependent. For the Group I ions this dependence is nonmonotonic in nature with injury increasing in the order Li+ less than Na+ less than Cs+ less than K+. Injury can be reduced by the inclusion in the freezing media of saccharide cryoprotectants or by the substitution with less injurious cations, e.g., Mg2+ or (CH3)4N+. In contrast to the situation observed with cations injury with anions follows Hofmeister lyotropic power series with injury increasing with decreasing hydrated ionic radius. Careful choice of electrolyte species allows injury to be reduced to levels comparable to that afforded by saccharide cryoprotectants. A possible mechanism for the nonmonotonic trends in injury observed with cations is considered.     

pH gradient across the lysosomal membrane generated by selective cation permeability and Donnan equilibrium.

The pH within isolated Triton WR 1339-filled rat liver lysosomes was determined by measuring the distribution of [14C]methylamine between the intra- and extralysosomal space. The intralysosomal pH was found to be approximately one pH unit lower than that of the surrounding medium. Increasing the extralysosomal cation concentration lowered the pH gradient by a cation exchange indicating the presence of a Donnan equilibrium. The lysosomal membrane was found to be significantly more permeable to protons than to other cations. The relative mobility of cations through the lysosomal membrane is H+ greater than Cs+ greater than Rb+ greater than K greater than Na+ greater than Li+ greater than Mg2+, Ca2+. The presented data suggest that the acidity within isolated Triton WR 1339-filled lysosomes is maintained by: (1) a Donnan equilibrium resulting from the intralysosomal accumulation of nondiffusible anions and (2) a selective permeability of the lysosomal membrane to cations.     

Threonine in the selectivity filter of the acetylcholine receptor channel.

The acetylcholine receptor (AChR) is a cation selective channel whose biophysical properties as well as its molecular composition are fairly well characterized. Previous studies on the rat muscle alpha-subunit indicate that a threonine residue located near the cytoplasmic side of the M2 segment is a determinant of ion flow. We have studied the role of this threonine in ionic selectivity by measuring conductance sequences for monovalent alkali cations and bionic reversal potentials of the wild type (alpha beta gamma delta channel) and two mutant channels in which this threonine was replaced by either valine (alpha T264V) or glycine (alpha T264G). For the wild type channel we found the selectivity sequence Rb greater than Cs greater than K greater than Na. The alpha T264V mutant channel had the sequence Rb greater than K greater than Cs greater than Na. The alpha T264G mutant channel on the other hand had the same selectivity sequence as the wild type, but larger permeability ratios Px/PNa for the larger cations. Conductance concentration curves indicate that the effect of both mutations is to change both the maximum conductance as well as the apparent binding constant of the ions to the channel. A difference in Mg2+ sensitivity between wild-type and mutant channels, which is a consequence of the differences in ion binding, was also found. The present results suggest that alpha T264 form part of the selectivity filter of the AChR channel were large ions are selected according to their dehydrated size.     

The influence of external cations and membrane potential on Ca- activated Na efflux in Myxicola giant axons

In microinjected Myxicola giant axons with elevated [Na]i, Na efflux was sensitive to Cao under some conditions. In Li seawater, sensitivity to Cao was high whereas in Na seawater, sensitivity to Cao was observed only upon elevation of [Ca]o above the normal value. In choline seawater, the sensitivity of Na efflux to Cao was less than that observed in Li seawater whereas Mg seawater failed to support any detectable Cao-sensitive Na efflux. Addition of Na to Li seawater was inhibitory to Cao-sensitive Na efflux, the extent of inhibition increasing with rising values of [Na]o. The presence of 20 mM K in Li seawater resulted in about a threefold increase in the Cao-activated Na efflux. Experiments in which the membrane potential, Vm, was varied or held constant when [K]o was changed showed that the augmentation of Ca- activated Na efflux by Ko was not due to changes in Vm but resulted from a direct action of K on activation by Ca. The same experimental conditions that favored a large component of Cao-activated Na efflux also caused a large increase in Ca influx. Measurements of Ca influx in the presence of 20 mM K and comparison with values of Ca-activated Na efflux suggest that the Na:Ca coupling ratio may be altered by increasing external [K]o. Overall, the results suggest that the Cao- activated Na efflux in Myxicola giant axons requires the presence of an external monovalent cation and that the order of effectiveness at a total monovalent cation concentration of 430 mM is K + Li greater than Li greater than Choline greater than Na.     

Influence of temperature on ionic sparing effect and cell-associated cations in the moderate halophile, Micrococcus varians var. halophilus

Cells of the moderately halophilic Micrococcus varians var. halophilus grew well in a chemically defined medium containing 1 to 3 M NaCl and 0.0103 M K+. The requirement for NaCl could be partially replaced by K+,:Li+ and Cs+. The efficiency of the sparing effect of these cations for NaCl was in order of K+ GReater than Li+ greater than Cs+. Increase in growth temperature was found to enchance the sparing effect of Li+ and Cs+ but not that of K+. Over the range of NaCl concentrations in which the cells grew well, cell-Na+ concentrations were similar to the medium NaCl concentrations while cellK+ concentrations were several-fold that in the medium. Cell-bound Na+ and K+ concentrations increased proportionally with medium NaCl concentration and growth temperature. The temperature-dependent cation accumulation was more obvious with K+ than Na+. The cell-associated Na+ + K+ concentrations were almost as high as or slightly higher than the external media which contained appropriate levels of NaCl regardless of the growth temperature.     

Cation selectivity of and cation binding to the cGMP-dependent channel in bovine rod outer segment membranes

The properties of the cGMP-dependent channel present in membrane vesicles prepared from intact isolated bovine rod outer segments (ROS) were investigated with the optical probe neutral red. The binding of neutral red is sensitive to transport of cations across vesicular membranes by the effect of the translocated cations on the surface potential at the intravesicular membrane/water interface (Schnetkamp, P. P. M. J. Membr. Biol. 88: 249-262). Only 20-25% of ROS membrane vesicles exhibited cGMP-dependent cation fluxes. The cGMP-dependent channel in bovine ROS carried currents of alkali and earth alkali cations, but not of organic cations such as choline and tetramethylammonium; little discrimination among alkali cations (K greater than Na = Li greater than Cs) or among earth alkali cations (Ca greater than Mn greater than Sr greater than Ba = Mg) was observed. The cation dependence of cGMP-induced cation fluxes could be reasonably well described by a Michaelis-Menten equation with a dissociation constant for alkali cations of about 100 mM, and a dissociation constant for Ca2+ of 2 mM. cGMP-induced Na+ fluxes were blocked by Mg2+, but not by Ca2+, when the cations were applied to the cytoplasmic side of the channel. cGMP-dependent cation fluxes showed a sigmoidal dependence on the cGMP concentration with a Hill coefficient of 2.1 and a dissociation constant for cGMP of 92 microM. cGMP-induced cation fluxes showed two pharmacologically distinct components; one component was blocked by both tetracaine and L-cis diltiazem, whereas the other component was only blocked by tetracaine.     

Origins of the transient anterior-posterior asymmetry in the frog lens fiber potential

The origin of the transient asymmetry of intracellular resting potentials between the anterior and posterior lens fibers was investigated in the isolated American bullfrog lens by a conventional microelectrode technique. In high K+, Rb+, Cs+, or NH+4 test solution applied only to the lens anterior or posterior side, anterior fibers depolarized at a slower rate than posterior ones. After a long exposure, however, the transient potential difference disappeared. The magnitude of the depolarizations of the lens fibers was in the order of K+ greater than Rb+ greater than Cs+ greater than NH+4. The resting potentials plotted as a function of external K+ concentrations ([K]0) were in agreement with Nernst equation predictions with a slope of 58 mV/decade ion concentration change. A small Na+ permeability is unmasked at a [K]0 less than 10 mM. It was concluded that the transient difference measured in potentials of anterior and posterior lens fibers on increasing external K+, Rb+, Cs+ or NH+4 depends on the anterior epithelial cell layer, which is a diffusional barrier for ions penetrating into the lens interior.     

Rapid release of 45Ca from an occluded state of the Na,K-pump

45Ca is bound to the occluded state of the Na,K-pump, apparently at K+ sites. Only one 45Ca ion is bound in place of two K+ ions, with an affinity approximately 0.08 mM; K+ competes with an apparent affinity approximately 0.04 mM. 45Ca is released rapidly from Na,K-ATPase in the presence of ATP or ADP, presumably to the intracellular medium. The rate constant of 45Ca release with ATP is greater than 100 s-1 at 20 degrees C, more than twice as fast as the rate of release of 42K from the occluded state. Phosphorylation of Na,K-ATPase with MgPi, which would lead to release of occluded K+ or Rb+ to the extracellular face of the membrane, stabilizes occluded 45Ca. 45Ca release is slower immediately after exposure to MgPi than after a rinse in the absence of Pi indicating that in the former circumstance the rate of 45Ca release is limited by dephosphorylation; 45Ca release is even slower after exposure to Mg2+ arsenate, consistent with dearsenylation being slower than dephosphorylation. When limited by dephosphorylation, the rate of 45Ca release is dependent on the species of monovalent cation present, increasing in the order N-methylglucamine less than Cs+ less than Li+ less than Na+ less than Rb+ less than K+. When the 45Ca occluded state is exposed to K + Mg + Pi and then to Na+ + Mg2+ + ATP, the exposure to K+ is "remembered," indicating simultaneous occlusion of 45Ca and K+. The apparent affinity for K+ in formation of this state is 10-50 mM, and the rate of release of K+ is approximately 2 s-1. Ca2+ has effects on the release of 86Rb from the occluded state: With ATP, Ca2+ acts like Mg2+ by stimulating 86Rb release at low concentrations and inhibiting at high concentrations; with MgPi, Ca2+ inhibits 86Rb release, presumably by preventing phosphorylation. Thus, Ca2+ has two actions on the Na,K-pump as studied here: one as a Mg2+ congener, and another as a K+ congener at transport sites. In the latter role Ca2+ is unusual in that it appears to be able to bind to the transport sites from the intracellular face of the pump and to become occluded, but unable to be released from extracellular sites.     

Effects of ATP and monovalent cations on Mg2+ inhibition of (Na,K)-ATPase

The hydrolysis of ATP catalyzed by purified (Na,K)-ATPase from pig kidney was more sensitive to Mg2+ inhibition when measured in the presence of saturating Na+ and K+ concentrations [(Na,K)-ATPase] than in the presence of Na+ alone, either at saturating [(Na,Na)-ATPase] or limiting [(Na,0)-ATPase] Na+ concentrations. This was observed at two extreme concentrations of ATP (3 mM where the low-affinity site is involved and 3 microM where only the catalytic site is relevant), although Mg2+ inhibition was higher at low ATP concentration. In the case of (Na,Na)-ATPase activity, inhibition was barely observed even at 10 mM free Mg2+ when ATP was 3 mM. When (Na,K)-ATPase activity was measured at different fixed K+ concentrations the apparent Ki for Mg2+ inhibition was lower at higher monovalent cation concentration. When K+ was replaced by its congeners (Rb+, NH+4, Li+), Mg2+ inhibition was more pronounced in those cases in which the dephosphorylating cation forms a tighter enzyme-cation complex after dephosphorylation. This effect was independent of the ATP concentration, although inhibition was more marked at lower ATP for all the dephosphorylating cations. The K0.5 for ATP activation at its low-affinity site, when measured in the presence of different dephosphorylating cations, increased following the sequence Rb+ greater than K+ greater than NH+4 greater than Li+ greater than none. The K0.5 values were lower with 0.05 mM than with 10 mM free Mg2+ but the order was not modified. The trypsin inactivation pattern of (Na,K)-ATPase indicated that Mg2+ kept the enzyme in an E1 state. Addition of K+ changed the inactivation into that observed with the E2 enzyme form. On the other hand, K+ kept the enzyme in an E2 state and addition of Mg2+ changed it to an E1 form. The K0.5 for KCl-induced E1-to-E2 transformation (observed by trypsin inactivation profile) in the presence of 3 mM MgCl2 was about 0.9 mM. These results concur with two mechanisms for free Mg2+ inhibition of (Na,K)-ATPase: "product" and dead-end. The first would result from Mg2+ interaction with the enzyme in the E2(K) occluded state whereas the second would be brought about by a Mg2+-enzyme complex with the enzyme in an E1 state.     

Effects of group I cations on the gelation of iota carrageenan

N.m.r. and rheological measurements have been used to study the gelation of iota carrageenan. Gelation has been found to occur only at polymer concentrations above the critical entanglement concentration. The high temperature sol state above the gel-sol transition appears to be an entangled polymer network. Although Li⁺ and Na⁺ ions are less effective at gelling the polymer than K⁺, Rb⁺ and Cs⁺ all cationic forms studied gel at sufficiently high polymer concentration and ionic strength. ⁷Li⁺, ²³Na, ³⁹K, ⁸⁷Rb and ¹³³Cs n.m.r. studies have been made as a function of temperature. The lithium salt form (2.2% w/w concentration) formed a viscoelastic solution at room temperature. The other salt forms gelled on cooling. The spectra of Li, Na and Cs carrageenan showed little change on heating whereas K and Rb spectra showed marked changes in apparent intensity. The nature of the cation interaction with the juntion zones is discussed.     

A comparative monomolecular film study of antibiotic A21978C homologues of various lipid chain length

A21978C is a calcium-dependent lipopeptide antibiotic whose biological properties are modulated by changes in its lipid chain length. This article reports on the monolayer characteristics of this cyclic lipopeptide and of LY146032 a semi synthetic homologue. The equilibrium spreading pressure pi e increases linearly with the ionic concentration of the subphase and is higher with divalent cations. The nature of the divalent cation plays a crucial role in the spreading as indicated by the variation in the molecular free energy delta Gs.delta Gs decreases in the order K+ greater than Mg2+ greater than Ca2+, which indicates privileged interactions with Ca2+. Also, the larger the lipid chain, the easier the spreading of antibiotic molecules. The compression isotherm curves are shown. The mean area of the uncompressed molecules is around 220-240 A 2 which is compatible with the size of the peptide cycle lying at the interface. The isotherm curves of the natural compounds show a transition region where the molecules are more compressible. At a given area/molecule, the surface pressures increase with the acyl chain length. When the molecules are spread on various salt solutions, the surface pressures increase in the order K+ less than Mg2+ less than Ca2+. The isotherm curves are not reversible upon a compression-expansion cycle and a wide amplitude hysteresis is observed. If a second compression is done, the curve shape is that of a liquid-expanded state and the transition region is no longer observed. This implies a conformational change of the molecules during the first compression process.     

Effects of Mg and Ca on the side dependencies of Na and K on ouabain binding to red blood cell ghosts and the control of Na transport by internal Mg

The effect of alteration in the concentration of internal Mg on the rate of ouabain binding to reconstituted human red blood cell ghosts has been evaluated as well as the effect of Mgi on Na:Na compared to Na:K exchange. It was found that the dependence of the rate of ATP-promoted ouabain binding on the combined presence of Nai and Ko which occurs at high [Mg]i is lost when the concentration of Mgi is lowered. The sensitivity of the external surface for Ko is also changed since Ko can now inhibit the ouabain binding rate in the absence of Nai; on the other hand Nao at low [Mg]i can stimulate ouabain binding indicating that the relative affinity of the outside surface for Nao has either increased or that for Ko has decreased or both. Thus the effects of changes in [Mg]i result in a change in the side-dependent actions of Na and K and emphasize the possible difficulties of interpreting results obtained on systems lacking sidedness. Mgi was found to be required for Pi-promoted ouabain binding and that the inhibitory action of Nai increased as [Mg]i was increased. In addition, Ca was found to be most effective in inhibiting the rate of ATP-promoted ouabain binding when Na and K were present together than when either was present alone. Na:K exchange was found to be more sensitive to the concentration of Mgi than Na:Na exchange; at low [Mg]i Na:K exchange could be stimulated without changing the extent of Na:Na exchange. These results are consistent with the idea that conformational states of the pump complex are directly influenced by [Mg]i.     

Permeability of Alkali Metal Cations in Lobster Muscle : A comparison of electrophysiological and osmometric analyses

Single muscle fibers from lobster walking legs are effectively impermeable to Na, but are permeable to K. They shrink in hyperosmotic NaCl; they swell in low NaCl media which are hyposmotic or which are made isosmotic with the addition of KCl. In conformity, the membrane potential is relatively insensitive to changes in external Na, while it responds according to the Nernst relation for changes in external K. When the medium is made isosmotic or hyperosmotic with RbCl the volume and membrane potential changes are of essentially the same magnitudes as those in media enriched with KCl. The time courses for attaining equilibrium are slower, indicating that Rb is less permeant than K. Substitution of CsCl for NaCl (isosmotic condition) produces no change in volume of the muscle fiber. Addition of CsCl (hyperosmotic condition) causes a shrinkage which attains a steady state, as is the case in hyperosmotic NaCl. Osmotically, therefore, Cs appears to be no more permeant than is Na. However, the membrane depolarizes slowly in Cs-enriched media and eventually comes to behave as an ideal Cs electrode. Thus, the electrode properties of the lobster muscle fiber membrane may not depend upon the diffusional relations of the membrane and ions, and the osmotic permeability of the membrane for a given cation may not correspond with the electrophysiologically deduced permeability. Comparative data on the effects of NH₄ and Li are also included and indicate several other degrees of complexity in the cell membrane.     

Permeability changes in the cytoplasmic membrane of Escherichia coli K-12 early after infection with bacteriophage T1.

The nature of the bacteriophage T1-induced changes in the permeability of the cytoplasmic membrane of Escherichia coli K-12 was investigated. At 20 degrees C and with glucose as a substrate, the addition of one bacteriophage per cell induced a complete and irreversible loss of K+ ions (single-hit phenomenon). K+ loss was compensated by an uptake of Na+, Li+, or choline by the cell, depending on which of these ions was the major cation in the medium. T1 depolarized the cells and inhibited 86Rb+-K+ exchange across the cytoplasmic membrane. The loss of K+ occurred independently of the Mg2+ concentration in the medium. By contrast, at low but not at high Mg2+ concentrations, T1 caused efflux of Mg2+ which in turn caused inhibition of respiration and a decrease of delta pH.