Action of surface-active substances on biological membranes V. Hemolytic,lytic and membrane-perturbing effects of N-lauroyl derivatives of amino acids with aliphatic side chains

Summary The hemolytic action of a number of N-lauroyl derivatives of amino acids with aliphatic side chains on human red cells has been examined. The agents' affinity for the red cell membrane and the mean number of the agent's molecules which, upon binding to an erythrocyte, make it undergo hemolysis have been measured. The relative hydrophobicity of the amino acids' residues under study estimated from the data on the surfactants' micellization has been considered in relation to the literature data. The contributions of the amino acids' side chains to the free energy of the agents' binding to the cell membrane and those to the free energy of the lytic interaction of the agents with the membrane have been evaluated.The effects of the surfactants on the red cell volume and that of N-lauroyl-leucine-Na on the volume of the differently prepared sealed ghosts have been studied.The lyric action of the surfactants has been measured and it is shown that the hemolytic and lytic capacities of an amphiphile appear to be in no relationship with each other.With 2 figures and 3 tables     

Trace metal analysis by anodic-stripping voltammetry Effect of surface-active substances

The presence of cationic, anionic, and neutral surfactants and humic substances is shown to affect the peak heights of copper, lead and cadmium in synthetic sea-water analysed by differential pulse anodic-stripping voltammetry. At surfactant concentrations below 0.1 mg/l. the effect is insignificant, but at higher concentrations the peak heights usually decrease, although for copper an increase in the peak height was also observed. The peak heights do not depend to any great extent on the pH of the solution, except in alkaline solution and in the presence of humic substances. Adsorption and complex formation may account for the observed dependences.     

Effect of pH on the binding of alkyl sulfates to gelatin

A surfactant-selective eletrode in which the membrane is an o-nitrotoluene phase containing a dissolved complex of cetyltrimethylammonium-dodecyl sulfate has been applied to investigations of the interaction between gelatin and alkyl sulfates as well as gelatin and alkyltrimethylammoniumions in dilute aqueous solutions.The binding isotherms were obtained by comparing emf-values obtained for surfactant in water to the electrode potentials in gelatin solutions plotted in terms of surfactant concentration.The binding of alkyl sulfates was measured as a function of pH at constant free surfactant concentration. At pH values 7 the degree of binding is indpendent of the pH of the solution. The level of binding of alkyl sulfates to gelatin increases strongly with increasing chain length of the alkyl sulfate. At pH values 6 the extent of binding increases steeply with decreasing pH. Octyl sulfate shows a very low level of binding even at low pH. Cationics show much weaker interactions with gelatin than anionic surfactants of comparable alkyl chain length.     

Structural analysis of protein complexes with sodium alkyl sulfates by small-angle scattering and polyacrylamide gel electrophoresis

Small-angle X-ray (SAXS) and neutron (SANS) scattering is used to probe the structure of protein-surfactant complexes in solution and to correlate this information with their performance in gel electrophoresis. Proteins with sizes between 6.5 to 116 kDa are denatured with sodium alkyl sulfates (SC(x)S) of variable tail lengths. Several combinations of proteins and surfactants are analyzed to measure micelle radii, the distance between micelles, the extension of the complex, the radius of gyration, and the electrophoretic mobility. The structural characterization shows that most protein-surfactant complexes can be accurately described as pearl-necklace structures with spherical micelles. However, protein complexes with short surfactants (SC(8)S) bind with micelles that deviate significantly from spherical shape. Sodium decyl (SC(10)S) and dodecyl (SC(12)S, more commonly abbreviated as SDS) sulfates result in the best protein separations in standard gel electrophoresis. Particularly, SC(10)S shows higher resolutions for complexes of low molecular weight. The systematic characterization of alkyl sulfate surfactants demonstrates that changes in the chain architecture can significantly affect electrophoretic migration so that protein-surfactant structures could be optimized for high resolution protein separations.     

Polymerization of surface-active monomers. I. Micellization and polymerization of higher alkyl salts of dimethylaminoethyl methacrylate

Micellization of cationic salts of dimethylaminoethyl methacrylate (DMAEMA) quaternized with n-alkyl bromides such as octyl, lauryl, myristyl, and stearyl bromide and their polymerizations were investigated. The critical micelle concentration (cmc) in water at 25°C was determined by electrical conductivity and dye(azobenzene) solubilization methods and the relation log(cmc) = 1.46–0.31N was obtained, where cmc is in mmol L^?1 and N corresponds to carbon number of alkyl bromides used for the monomer preparations. All of these monomeric salts exhibited a high radical polymerizability in water and benzene. The polymerizations in water appeared to proceed with a higher rate with increasing a chain length of the alkyl moiety of the monomers and those in benzene gave the polymers with a remarkably high viscosity. The rate of polymerization of lauryl bromide salt in anisotropic solutions (in water and benzene) was exceedingly fast as compared with that in isotropic solution(in acetonitrile). All of the polymers obtained here were insoluble in water. Solubility characteristics of these monomers and polymers in other solvents were also presented. The reduced viscosity, in dimethylformamide and methanol, of poly(lauryl bromide salt) prepared in water increased with dilution but that for the polymer obtained in benzene exhibited an inverse concentration dependence. Some discussions were made on the peculiarities of the polymerizations of these monomers and the resulting polymers.     

Estimation of the critical micelle concentrations and the aggregation numbers of sodium alkyl sulfates by capillary-type isotachophoresis

The analytical procedure for the separation and quantification of bulk and micellar phases for sodium alkyl sulfates has been investigated by a capillary-type isotachophoresis using a potential gradient detector. Monomer solutions were distinguished from micellar solutions at pH 5.5–6.0; hydrochloric acid — L-Histidine mixture was used as the leading electrolyte and 2-(N-Morpholino) ethanesulfonic acid as the terminating electrolyte.The potential unit value (PU value) due to the monomer solutions was larger than that due to the micellar solutions. The zone length due to monomer solutions increased with increasing concentration of surfactant until a given concentration (CMC); beyond this point the values became constant. On the other hand, the zone length due to micellar solutions increased from this point. We report an applicability of capillary-type isotachophoresis to determination of the CMC's and aggregation number for various sodium alkyl sulfates.     

Identification of chemical substances by testing and screening of hypotheses. I. General

The characteristic features and the constituents of an identification procedure for chemical substances are discussed. This procedure is a screening of identification hypotheses followed by experimental testing of each one. The testing operation consists of comparison of the values of the quantities measured with other measurement results or reference data, resulting in the Student's ratio, the significance level, the matching of spectra, etc. The performance and the correctness of identification are expressed as "identification uncertainty", i.e. the probability of incorrect identification. The statistical significance level and other similarity values in spectra, chromatography retention parameters, etc. are the particular measures of uncertainty. Searching of prior data and estimation of the prior probability of the presence of particular compounds in the sample (matrix) to be analysed simplifies the setting up and cancelling of hypotheses during screening. Usually, identification is made by the analyst taking into account measurement results, prior information and personal considerations. The estimation of uncertainty and rules for the incorporation of prior data, make the result of identification less subjective.     

Identification of chemical substances by testing and screening of hypotheses I. General

The characteristic features and the constituents of an identification procedure for chemical substances are discussed. This procedure is a screening of identification hypotheses followed by experimental testing of each one. The testing operation consists of comparison of the values of the quantities measured with other measurement results or reference data, resulting in the Student’s ratio, the significance level, the matching of spectra, etc. The performance and the correctness of identification are expressed as “identification uncertainty”, i.e. the probability of incorrect identification. The statistical significance level and other similarity values in spectra, chromatography retention parameters, etc. are the particular measures of uncertainty. Searching of prior data and estimation of the prior probability of the presence of particular compounds in the sample (matrix) to be analysed simplifies the setting up and cancelling of hypotheses during screening. Usually, identification is made by the analyst taking into account measurement results, prior information and personal considerations. The estimation of uncertainty and rules for the incorporation of prior data, make the result of identification less subjective.     

Effect of surface-active substances on the surface charge density of purple membrane fragments

The surface charge density of purple membrane fragments and its alteration upon treatment of purple membranes with several surface-active substances [sodium dodecyl sulphate (SDS), cetylpyridinium chloride (CPC) and 3-[(3-cholamidopropyl) dimethylammonio]-1-propane-sulphonate (CHAPS) were examined by use of 9-amino-acridine fluorescence.The value of the surface charge density of native purple membrane fragments (0.8 electric charges/nm²) obtained by this method is comparable to previously reported values and in agreement with the structural model of the purple membrane.An increase followed by a decrease in the negative surface charge density was observed after treatment of purple membranes with the negatively charged surfactant SDS within the concentration range 0–5 mM, whereas treatment with the positively charged surfactant CPC and zwitterionic derivative of cholic acid (CHAPS) led to a decrease in the surface charge density. The large reduction of the surface charge density after treatment of purple membranes with CHAPS (i.e. partial delipidation of purple membranes) proves the significant contribution of the negative charges of the lipid polar head groups to the negative surface charge of purple membranes.     

Surface modification of polyacrylonitrile-based membranes by chemical reactions to generate phospholipid moieties

A novel approach for the surface modification of poly(acrylonitrile-co-2-hydroxyethyl methacrylate) (PANCHEMA) membranes by introducing phospholipid moieties is presented, which involved the reaction of the hydroxyl groups on the membrane surface with 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) followed by the ring-opening reaction of COP with trimethylamine. The chemical changes of phospholipid-modified acrylonitrile-based copolymers (PMANCP) membranes were characterized by Fourier transfer infrared spectroscopy and X-ray photoelectron spectroscopy. The surface properties of PMANCP membranes were evaluated by pure water contact angle, protein adsorption, and platelet adhesion measurements. Pure water contact angles measured by the sessile drop method on PMANCP membranes were obviously lower than those measured on the PANCHEMA membranes and decreased with the increase of the content of phospholipid moieties on the membrane surface. It was found that the bovine serum albumin adsorption and platelet adhesion were suppressed significantly with the introduction of phospholipid moieties on the membranes surface. These results demonstrated that the described process was an efficient way to improve the surface biocompatibility for the acrylonitrile-based copolymer membrane.     

Effect of bending and stretching of polyethylene strips on the adsorption of surface-active substances

The adsorption of tritium-labeled sodium stearate and ³⁵S-labeled sodium dodecylsulfate from aqueous solution on bent and on stretched polyethylene strips was directly measured. The amount of adsorption increased from 2.5 to 4.5 times on surfaces of various polyethylene samples stretched from 5.2 to 5.3 times the original length. For one sample, adsorption increased 8 and 2.5 times, respectively, on the convex and concave surfaces of a bent strip. Autoradiographs of the strips taken after adsorption revealed the appearance of both homogeneous and heterogeneous adsorption on the stretched surface of the polyethylene. The electron micrographs of the strips showed that many small fissures, about 1–5μ in length, formed on their surfaces after the strips were bent or stretched. Enhanced adsorption of the surface-active substance along these fissures was suggested. On the basis of these observations, it is proposed that in stretching or bending, fissures increase adsorption of the detergent, and the adsorption in turn promotes further development of fissures. Thus, bending and adsorption mutually promote the growth of fissures which finally result in failure of the polyethylene.     

Effect of sulfadiazine on biological model membranes

Summary In this paper the optimization of the kaolin calcination is studied, aiming at using the produced metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of metakaolins and finally by strength development analysis of cement-metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO₃. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive metakaolins.     

Studies on the chemical modification of monensin. IV. Synthesis, sodium ion permeability, and biological activity of 7-O-acyl- and 7-O-alkylmonensins.

7-O-Acyl-(4a-e) and 7-O-alkylmonensins (5a-d) were prepared from monensin (1). Their lipophilicity, sodium ion permeability in human erythrocytes, antibacterial activity and effect on rat tail artery were examined. There was a correlation between lipophilicity and sodium ion permeability as well as between lipophilicity and antibacterial activity. We also found that the compound having larger sodium ion permeability, showed stronger contraction of rat tail artery. 7-O-Benzylmonensin (5c) exhibited higher lipophilicity and larger sodium ion permeability than monensin (1) among the tested monensin derivatives. In addition, antibacterial activity and contractile effect on rat tail artery of 5c were comparable to those of 1.