Aharon Katchalsky

Thermodynamic analysis of the permeability of biological membranes to non-electrolytes.

The application of the conventional permeability equations to the study of biological membranes leads often to contradictions. It is shown that the equations generally used, based on two permeability coefficients—the solute permeability coefficient and the water permeability coefficient—are incompatible with the requirements of thermodynamics of irreversible processes. The inconsistencies are removed by a thermodynamic treatment, following the approach of Staverman, which leads to a three coefficient system taking into account the interactions: solute-solvent, solute-membrane and solvent-membrane. The equations derived here have been applied to various permeability measurements found in the literature, such as: the penetration of heavy water into animal cells, permeability of blood vessels, threshold concentration of plasmolysis and relaxation experiments with artificial membranes. It is shown how the pertinent coefficients may be derived from the experimental data and how to choose suitable conditions in order to obtain all the required information on the permeability of the membranes. The significance of these coefficients for the elucidation of membrane structure is pointed out.

Interaction of basic polyamino acids with the red blood cell I. combination of polylysine with single cells

Abstract 1. 1. The interaction between negatively charged cells and positively charged (basic) polyelectrolytes is mainly due to non-specific electrostatic attractive forces. 2. 2. Adsorption of polylysine (PL) on the red blood cell is a reversible reaction which rapidly attains a state of equilibrium; consequently the surface potential of the erythrocyte in PL solutions is a single-valued function of the equilibrium concentration of free PL in solution. 3. 3. A method is described whereby mobility data can be used to evaluate both the concentration of PL in solution and the amount adsorbed on the cells. 4. 4. An adsorption isotherm of the Freundlich type was obtained which is characteristic of the interaction of PL with the red blood cell at pH 7.2 and ionic strength 0.15. 5. 5. With red blood cells, PL is bound by the membrane only. 6. 6. PL adsorption on the surface of glass particles and their electrophoretic mobilities were measured. 7. 7. The orientation, and the hemolytic effect, of PL molecules adsorbed on the red cell membrane are discussed.

Principles of receptor physiology

1 Mechano-Chemical Conversion.- 2 Proteins in Bioelectricity. Acetylcholine-Esterase and -Receptor.- 3 Transmission Action on Synaptic Neuronal Receptor Membranes.- 4 The General Electrophysiology of Input Membrane in Electrogenic Excitable Cells.- 5 Formation of Neuronal Connections in Sensory Systems.- 6 The Relation of Physiological and Psychological Aspects of Sensory Intensity.- 7 Sensory Power Functions and Neural Events.- 8 Generation of Responses in Receptor.- 9 Mechano-electric Transduction in the Pacinian Corpuscle. Initiation of Sensory Impulses in Mechanoreceptors.- 10 A Biophysical Analysis of Mechano-electrical Transduction.- 11 Responses of Nerve Fibers to Mechanical Forces.- 12 The Early Receptor Potential.- 13 The Nature of the Photoreceptor in Phototaxis.- 14 Sensory Transduction in Hair Cells.- 15 Transducer Properties and Integrative Mechanisms in the Frogs Muscle Spindle.- 16 Static and Dynamic Behavior of the Stretch Receptor Organ of Crustacea.- 17 Patterns of Organization of Peripheral Sensory Receptors.- Author Index.

Agglutination by polylysine of young and old red blood cells

Abstract The rate of agglutination by polylysine of young and old human erythrocytes was automatically recorded and correlated with measurements of the electrophoretic mobility of these cells. Old red cells have a lower electrophoretic mobility than young cells, as well as a higher rate of agglutination than young cells. Mild treatment of red cells with receptor destroying enzyme, which reduces their surface charge, results in an increased rate of agglutination. The results indicate that there is correlation between the rate of agglutination and the surface charge of the red cell.

Polycondensation of amino acid phosphoanhydrides: III. Polycondensation of alanyl adenylate

Abstract This paper reports an investigation on the behavior of alanyl adenylate in aqueous solution. It has been found that the mixed anhydride undergoes a relatively slow hydrolysis in the acidic pH range, whilst it polymerizes rapidly to give peptides at pH values higher than 7. The hydrolysis in the acidic range obeys a simple first-order reaction, and the hydrolytic constants can be determined directly from the kinetic run. In the basic range where there are two competitive reactions, hydrolysis and polymerization, evaluation of the constants for both reactions has been carried out by applying formulae derived by Katchalsky and Ailam in Part I of this series. It has been found that both the hydrolytic and polymerization constants increase with the pH. A correlation has been found between the polymerization constants of alanine, or its peptides, and their respective p K value. This correlation indicates that the reacting groups are the unionized amino groups of the amino acid moieties.

Polycondensation of amino acid phosphoanhydrides: II. Polymerization of proline adenylate at constant phosphoanhydride concentration

Abstract This study is devoted to the polymerization of proline adenylate to oligopeptides. The polymerization was carried out at pH 8.5 maintaining a steady-state concentration of the active phosphate. It was found that every degree of polymerization reaches a steady concentration after a relaxation time increasing with the degree of polymerization. From the time dependence of the concentrations and the steady level it was possible to evaluate the hydrolytic constant k h = 0.1 min −1 and the polymerization constant for dimer formation k 1 = 3.65 l · mole −1 ·min −1 , for trimer formation k 2 = 5.4 l · mol −1 · min −1 , for tetramer k 3 = 8.8 l · mole −1 · min −1 and for the pentamer k 4 = 10.7 l · mole −1 · min −1 . For higher degrees of polymerization the constants approach an approximately equal k value. Alternative runs of polymerization with different yields could be obtained by adding free proline to the solution of phosphoanhydride. All the results follow the same theoretical description and can be adequately represented by the same set of rate constants.

Hysteresis and Molecular Memory Record

The problem of memory and learning is discussed on the basis of a concise review of our present knowledge in this intriguing field of behavioral research. The results of a great variety of biochemical and biophysical studies support the current comprehension that biological information storage has a chemical molecular basis. Before a biosynthetic consolidation of phenotypic memory takes, however, place, there must be a physical interaction between the electric impulses of the neuronal network with an already existing molecular matrix. A mechanism proposed for fast imprint with low energy expenditure comprises conformational metastability (in certain cases leading to hysteretic phenomena) and conformational changes in macromolecules and macromolecular organizations such as membranes. Some physico-chemical aspects of a molecular memory system are discussed and a biopolyelectrolytic model system is described.

Synthesis of amino acyl-adenylates under prebiotic conditions.

SummaryIn a system containing zeolites, ATP and amino acids, amino acid-ADP anhydrides are able to form in an aqueous medium at neutral pH and room temperature. When montmorillonite, a clay possessing swelling properties, is added, polypeptides are formed. It is suggested that this may be the mechanism whereby prebiotic synthesis of peptides took place.

The effect of the carrier association-dissociation rate on membrane permeation

Abstract A system of facilitated diffusion is described in which a nonelectrolyte diffuses through the membrane and simultaneously undergoes an association-dissociation reaction with a carrier to form a substrate-carrier complex. The reaction which takes place throughout the membrane facilitates the diffusion. Mathematical expressions for the flow and chemical reaction profiles through the membrane are derived. Criteria are developed to determine whether chemical equilibrium is attained at the membrane surfaces. An expression is derived for the total flow as a function of concentration difference of the permeant across the membrane. The theoretical result is compared with the equations for carrier-mediated transport in which the permeant reacts at the surface only (discontinuous carrier model). An additional model is introduced in which the carrier is assumed to be an allosteric protein undergoing conformational changes within the membranes. In this model the flow of permeant is found to be an asymmetrical function of concentration differences.

Kenetics of aldose-amino acid interaction

Abstract 1. 1. The kinetics of the reaction between various aldoses and amino acids and peptides has been investigated. 2. 2. A method for the determination of rate constants, based on the addition of alkali to keep the pH of the reaction mixture constant, has been developed. 3. 3. The velocity of the reaction decreases with increase of pH according to the equation dRG − d t = R − .G kα + kβ .OH − − RG − (kα + kβ .OH − )L where RG − is the concentration of the reaction product, R − —that of the amino acid anion, G—of the aldose; OH − —the hydroxyl ion concentration and k α , k β pH independent rate constants. 4. 4. The rate constant k β is inversely proportional to the rate constant of the primary attack of the amino acid on the aldose. The rate of the primary reaction increases with the basicity of the amino component in accordance with the Hammett relation.