Action of surfactants on egg lecithin liposomes

The lytic action of several homologous series of surfactants including N-acyl derivatives of the Na-salt of amino acids on the egg lecithin multilamellar liposomes was examined. The affinity for the lipid membrane and the solubilising capacity of the agents were estimated. The contribution of a CH₂ group and that of the polar head group of surfactants to the free energy of the agent's binding to the membrane were evaluated. The results obtained indicate that the contribution of a CH₂ group to the free binding energy depends on the nature of the surfactants' head group. This dependence is attributed to either various localisation of the agent's molecules in the lipid bilayer or to different properties of the agent's hydrocarbon tails. The contributions of the head groups of the surfactants are assumed to reflect the affinity of these head groups for the lecithin polar head group at the membrane interface. The results obtained indicate some degree of specificity involved in the interactions of the head groups.     

A dodecamer of globin chains is the principal functional subunit of the extracellular hemoglobin of Lumbricus terrestris

Repeated dissociation of the approximately 3600-kDa hexagonal bilayer extracellular hemoglobin of Lumbricus terrestris in 4 M urea followed by gel filtration at neutral pH produces a subunit that retains the oxygen affinity of the native molecule (approximately 12 torr), but only two-thirds of the cooperativity (nmax = 2.1 +/- 0.2 versus 3.3 +/- 0.3). The mass of this subunit was estimated to be 202 +/- 15 kDa by gel filtration and 202 +/- 26 kDa from mass measurements of unstained freeze-dried specimens by scanning transmission electron microscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this subunit showed that it consists predominantly of the heme-containing subunits M (chain I, 17 kDa) and T (disulfide-bonded chains II-IV, 50 kDa). Mixing of subunits M and T isolated concurrently with the 200-kDa subunit resulted in partial association into particles that had a mass of 191 +/- 13 kDa determined by gel filtration and 200 +/- 38 kDa determined by scanning transmission electron microscopy and whose oxygen affinity and cooperativity were the same as those of the 200-kDa subunit. The results imply that the 200-kDa subunit is a dodecamer of globin chains, consisting of three copies each of subunits M and T (3 x chains (I + II + III + IV], in good agreement with the mass of 209 kDa calculated from the amino acid sequences of the four chains, and represents the largest functional subunit of Lumbricus hemoglobin. Twelve copies of this subunit would account for two-thirds of the total mass of the molecule, as suggested earlier (Vinogradov, S. N., Lugo, S. L., Mainwaring, M. G., Kapp, O. H., and Crewe, A. V. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 8034-8038). The retention of only partial cooperativity by the 200-kDa subunit implies that full cooperativity is dependent on the presence of a complete hexagonal bilayer structure, wherein 12 200-kDa subunits are linked together by approximately 30-kDa heme-deficient chains.     

The structure of the O-antigenic polysaccharide from lipopolysaccharide of Vibrio cholerae strain H11 (non-O1).

After acid degradation of the lipopolysaccharide (LPS) of Vibrio cholerae strain H11 (non-O1), a tetrasaccharide was obtained, the structure of which was determined by quantitative and methylation analyses, periodate oxidation, one- and two-dimensional NMR spectroscopy, and fast-atom-bombardment and four-sector tandem mass spectrometry as beta-D-GalANGro-(1-3)-beta-D-QuiNAc-(1-4)-alpha-D-GalANGr o-(1-4)-NeuAc, in which GalANGro is N-galacturonoyl-2-aminoglycerol and QuiN 2-amino-2,6-dideoxy-glucopyranose. In addition, the trisaccharide beta-D-GalANGro-(1-3)-beta-D-QuiNAc-(1-4)-D-altro-hept ulose and the disaccharide alpha-D-GalANGro-(1-4)-NeuAc were isolated from acid-degraded lipopolysaccharide; the occurrence of sedoheptulose in lipopolysaccharide has not been described before. Based on the result of methylation analysis showing that galacturonic acid was the terminal sugar of the polysaccharide chain, and on the assumption that the tri- and the disaccharide represented the reducing and the non-reducing ends of the polysaccharide, respectively, the chemical structure of the O-specific chain of V. cholerae H11 is proposed as alpha-D-GalANGro-(1-4)-alpha-NeuAc-(2-3)-beta-D-GalANGro-(1- 3)-beta-D-QuiNAc- (1-[4)-alpha-D-GalANGro-(1-4)-alpha-NeuAc-(2-3)-beta-D-GalANGro -(1-3)-beta-D- QuiNAc-(1-]n-(1-4)-D-altro-heptulose. However, other possible structures can not be ruled out since the tri- and the disaccharide could be localised at different positions.     

Ultrastructure of the interstitial cells of the renal papilla in the white rat

Interstitial cells of the renal papilla have the phenotypic appearance, being more of a fibroblast than of a histiocyte character. Interstitial cells differ from the "typical fibroblasts" in the number of lipid droplets, in the development of cisternae of the Golgi complex and rough endoplasmic reticulum, and in the number of lysosome-like bodies and mitochondria.     

Possibility of analytical application of the partition in aqueous biphasic polymeric systems technique

The partition behaviour of a number of ionic and nonionic surface-active substances in the dextran-polyethylene glycol system was examined. The strictly linear dependence of the logarithm of the partition coefficient on the alkyl chain length for a homologous series of nonionic surfactants provides a measure of the difference in the relative hydrophobicity between the two phases of the system, in terms of the free energy of transfer of a CH₂ group from the bottom phase to the top phase of the system. This difference is found to be altered in the presence of NaCl or KCl depending on the salt concentration. It is concluded that the influence of the salt composition of the system on the distributed solutes' behaviour may be due to the effect of the ions on the hydrophobicity difference between the phases.The partition of ionic amphiphiles is found to be dependent on the relative hydrophobicity of the compounds as well as on their charge. It is shown that at salt concentrations up to about 0.1 M NaCl the charged solute partition is determined by its charge as well as its relative hydrophobicity, in the presence of 0.1–0.2 M NaCl the substance distribution is highly dependent on its charge and slightly on its lipophility. At the salt concentrations above 0.2 M the solute partition is determined just by its hydrophobic character and seems to be totally independent of its charge. It is concluded that the partition technique can be used for analytical purposes. The method seems to be unique in providing quantitative information on the amphiphilic surface properties of the solutes being partitioned.     

Kinetics of the inhibition of succinate dehydrogenase in bull adrenal cortex by malonate and oxaloacetate

The activity of succinate dehydrogenase from bull adrenal cortex was studied as affected by malonate and oxaloacetate. The both substrate analogs without preincubation (separately and in the mixture) inhibit the enzyme by the competitive type. After a 3 min oxaloacetate preincubation of the enzyme inhibition is of a mixed character. Malonate under these conditions lowers the oxaloacetate effect without changing the type of inhibition. It is supposed that the protective effect is due to a high rate of formation and decay of the enzyme-inhibitory malonate complex.     

The myriapodological legacy of Victor Ivanovich Motschoulsky (1810–1871)

The little that remains of Motschoulsky’s myriapodological legacy in the collection of Moscow’s Zoological Museum proves to be of very limited value. Only one species of Diplopoda described by Motschoulsky, the Caucasian Hirudisoma roseum (Victor, 1839), is still in use, yet requiring a neotype designation, whereas the remaining few myriapod names he proposed are either nomina dubia or nomina nuda. The former include Scolopendra pentagramma Motschoulsky, 1866 (Chilopoda, Scolopendromorpha, Scolopendridae) and Strongylosoma carinulatum Motschoulsky, 1866 (Diplopoda, Polydesmida, Paradoxosomatidae), both from Japan, as well as Julus costulatus Motschoulsky, 1851 (Diplopoda, Callipodida, Schizopetalidae?), from Montenegro, because their type material is either inadequate or missing.     

The genetic diversity and phylogeny of green microalgae in the genus Choricystis (Trebouxiophyceae,Chlorophyta) in Lake Baikal

Limnology - Green microalgae are of the utmost importance to aquatic ecosystems globally, as they are primary producers and major food sources for many organisms. Microalgae of the genus...