A 1h And 13c Magnetic Resonance And Infrared Spectroscopic Study Of Coordinated 2-Aminocyclopentene-1-Dithiocarboxylic Acid And Its S-Methyl Ester

The ligating properties of 2-aminocyclopentene-1-dithiocarboxylic acid and its S-methyl esters were investigated. Complexes with Zn(II), Cd(II) and Hg(II) halides were synthesized and characterized by infrared and proton and carbon-13 NMR studies. The results are concordant with a bidentate coordination of the -CS2 group to the metal ions

Energy-dependence of nitrate reductase induction in Candida-Utilis

The requirement of a suitable energy source during the induced synthesis of nitrate reductase in Image was investigated. The levels of nitrate reductase induced were shown to be energy-dependent, and to vary in response to the type of carbon source provided. Glycerol, fructose, ethanol, glucose, and sucrose served as efficient energy sources. Growth rate of the yeast and the induced level of nitrate reductase were dependent on the ratio of carbon to nitrogen in the induction medium, and ratio of 2 being optimal. Induction of nitrate reductase was inhibited by uncouplers, 2,4-dinitrophenol (DNP), dicumarol and carbonyl cyanide Candida-Utilis -trifluoromethoxy phenyl hydrazone (CCCP), and by cyanide and azide, indicating an absolute energy-dependency. The facilitation of induction of a high level of nitrate reductase by exogenously added ATP as sole source of energy confirmed the obligate requirement of ATP for the synthesis of nitrate reductase in Candida-Utilis.

Bull sperm plasma and acrosomal membranes: Fluorescence studies of lipid phase fluidity

Bull sperm plasma and outer acrosomal membranes have been isolated by discontinuous sucrose density gradient centrifugation and Ca2+-ATPase activity has been determined for both the membranes. Pyrene excimer fluorescence and diphenylhexatriene fluorescence polarization studies show that the lipid phase of the sperm plasma membranes is more fluid than the lipids of the outer acrosomal membranes. Approximately, a three fold increase in the cholesterol content has been found in the outer acrosomal membranes as compared to that in the plasma membranes.

Regional differentiationnext term in previous termbull sperm plasma membranesnext term

previous termBull spermnext term heads and tails have been separated by proteolytic digestion (trypsin) and previous termplasma membranesnext term have been isolated, using discontinuous sucrose density gradient centrifugation. previous termPlasma membranenext term bound Ca2+-ATPase is shown to be associated mostly with the tail previous termmembranes.next term Pyrene excimer fluorescence and diphenylhexatriene fluorescence polarization experiments indicate a more fluid lipid phase in the tail region. Differences in surface charge distribution have been found, using 1-anilinonaphthalene-8-sulfonate and Tb3+ as fluorescent probes.

Cholesterol-Esterifying Enzymes in Developing Rat Brain

A cholesterol-esterifying enzyme which incorporates exogenous fatty acids into cholesterol esters in the presence of ATP and coenzyme A was demonstrated in 15-day-old rat brain. This enzyme was maximally active at pH 7.4 and distinct from the cholesterol-esterifying enzyme reported earlier (Eto and Suzuki, 1971), which has a pH optimum at 5.2 and does not require cofactors. Properties of the two enzymes have been compared. Both the enzymes showed negligible esterification with acetate and were maximally active with oleic acid. The pH 5.2 enzyme esterified desmosterol, lanosterol and cholesterol at about the same rate, while the pH 7.4 enzyme was only 50% as active ith lanosterol as it was with cholesterol and desmosterol. Phosphatidyl serine stimulated the pH 5.2 enzyme but not the pH 7.4 enzyme. Phosphatidyl choline and sodium taurocholate showed no effect on either of the enzymes. Both the enzymes were associated with particulate fractions, but the pH 7.4 enzyme was localized more in the microsomes. Purified myelin showed 2.6-fold and 1.5-fold higher specific activities of pH 5.2 and 7.4 enzymes respectively, when compared with homogenate. About 7-10% of total activity of both the enzymes was associated with purified myelin. Brain stem and spinal cord showed higher specific activity of pH 5.2 enzyme than cerebral cortex and cerebellum, while pH 7.4 enzyme specific activity was higher in cerebellum and brain stem than in cerebral cortex and spinal cord. Microsomal pH 7.4 activity showed progressive increase prior to the active period of myelination, reaching a maximum on the 15th day after birth and declined to 20% of the peak activity by 30 days. In contrast, pH 5.2 enzyme reached maximum activity about the 6th day after birth and remained at this level well into adulthood. In 15-day-old rat brain, pH 7.4 enzyme had five to six times higher specific activity than pH 5.2 enzyme, while in adults the activities were equal. The pH 7.4 enzyme showed a threefold higher specific activity than pH 5.2 enzyme in myelin from 15-day-old rats, but in adults the reverse was true. Key Words: Cholesterol esterifying enzymes-Developing rat brain-Myelination. Jagannatha H. M. and Sastry P. S. Cholesterol-esterifying enzymes in developing rat brain. J. Neurochem. 36, 1352- 1360 (1981).

Inhibition of H2O2 generation in rat liver mitochondria by radical quenchers and phenolic compounds

Generation of H2O2 by rat liver mitochondria with choline, glycerol 1-phosphate and proline as substrates has been shown by using high-concentration phosphate buffer. Rates obtained under these conditions were higher and more consistent as compared with the earlier reports with high-concentration mannitol/sucrose/Tris buffer. Sulphate ions could replace phosphate indicating a requirement for a high concentration of oxygen-containing anions. H2O2 generation was dependent on the presence of native mitochondria and substrate. Maximal rates with various substrates were found to be the same as with succinate. Values of Km and Vmax for H2O2 generation were considerably less than those obtained for respective dehydrogenase activities, measured by dye reduction. Scavengers of O2-. and OH. inhibited generation of H2O2. ATP, ADP, thyronine derivatives and a number of phenolic compounds also showed very potent inhibitory effects of H2O2 generation, whereas phenyl compound had no effect. Phenolic compounds did not have any effect on mitochondrial superoxide dismutase and choline dehydrogenase activities as well as on O2-. generation by the xanthine-xanthine oxidase system. Inhibition by phenolic compounds may have potential for regulation of the intracellular concentration of H2O2, that is not considered to have a "second messenger' function.

Metallomicelles as potent catalysts for the ester hydrolysis reactions in water

Synthetic amphiphiles have been employed for the investigation of diverse topics, e.g. membrane mimetics, drug delivery, ion sensing and even in certain separation processes. Metal-complexing amphiphiles comprise an interesting class of compounds possessing multiple utilities. Upon solubilization in water they form metallomicelles. For achieving specific catalysis of a variety of reactions, metallomicelles were utilized by applying the principles of coordination chemistry and self-organizing systems. Because of their certain similarities with the natural enzymes, metallomicelles were synthesized as catalysts for many reactions. In particular the metallomicelles play a catalytic role in reactions involving the hydrolysis of activated carboxylate esters, phosphate esters and amides at ambient conditions near neutral pH. Apart from the hydrolysis reactions, these were exploited to play pertinent role as Lewis acid catalysts in cycloaddition reactions, and in other reactions such as phenolic oxidation in presence of hydrogen peroxide. In this review we emphasize with the help of assorted examples, the design, synthesis of metal-complexing amphiphiles and their aggregation behavior leading to catalytic hydrolysis reactions in aqueous media.

Alamethicin and synthetic peptide fragments as uncouplers of mitochondrial oxidative phosphorylation. Effect of chain length and change

Alamethicin, its derivatives and some synthetic fragments have been shown to be uncouplers of oxidative phosphorylation in rat liver mitochondria. A minimum peptide chain length of 13 residues is necessary for this activity. Peptide esters are more efficient uncouplers than the corresponding peptide acids. Esterification of the Glu(18) γ-COOH group in alamethicin does not diminish uncoupling activity. The structural requirements for uncoupling activity parallel those determined for ionophoretic action in small, unilamellar liposomes. Aib, α-aminoisobutyric acid; Z, benzyloxycarbonyl; OMe, methyl ester; OBz, benzyl ester; Ac, acetyl; CTC, chlortetracycline.

Regional differentiation in bull sperm plasma-membranes

Bull sperm heads and tails have been separated by proteolytic digestion (trypsin) and plasma membranes have been isolated, using discontinuous sucrose density gradient centrifugation. Plasma membrane bound Ca2+-ATPase is shown to be associated mostly with the tail membranes. Pyrene excimer fluorescence and diphenylhexatriene fluorescence polarization experiments indicate a more fluid lipid phase in the tail region. Differences in surface charge distribution have been found, using 1-anilinonaphthalene-8-sulfonate and Tb3+ as fluorescent probes.

N-Urethane-Protected Amino Alkyl Isothiocyanates: Synthesis, Isolation, Characterization, and Application to the Synthesis of Thioureidopeptides

Synthetically useful N-Fmoc amino-alkyl isothiocyanates have been described, starting from protected amino acids. These compounds have been synthesized in excellent yields by thiocarbonylation of the monoprotected 1,2-diamines with CS2/TEA/p-TsCl, isolated as stable solids, and completely characterized. The procedure has been extended to the synthesis of amino alkyl isothiocyanates from Boc- and Z-protected amino acids as well. The utility of these isothiocyanates for peptidomimetics synthesis has been demonstrated by employing them in the preparation of a series of dithioureidopeptide esters. Boc-Gly-OH and Boc-Phe-OH derived isothiocyanates 9a and 9c have been obtained as single crystals and their structures solved through X-ray diffraction. They belong to the orthorhombic crystal system, and have a single molecule in the asymmetric unit (Z′ = 1). 9a crystallizes in the centrosymmetric space group Pbca, while 9c crystallizes in the noncentrosymmetric space group P212121.

Mechanistic studies on the action of ammonium phosphate on polymer fire retardancy

The mechanism of fire retardant action of mono- and diammonium phosphates on polystyrene has been investigated. Ignition delay and mass burning rate studies reveal that the phosphates bring down both parameters considerably though to different extents. This has been adequately explained on the basis of the existing combustion models and physicochemical behavior of the material. Similar to their action on cellulosic materials, phosphates bring about fire retardancy in polystyrene via char formation. This is suggested to occur through a series of processes consisting of initial peroxide formation, decomposition to alcohols and aldehydes, formation of alkyl-phosphate esters, dehydration and subsequent char formation. Infrared and mass spectral studies support this mechanism.

Anisochrony of O-methylene protons of ethyl ester functions and structural factors in the connected chiral entities

(i) Incistrans pairs of cyclic 1,3-dicarboxylic acid ethyl esters thecis-foms exhibit higher O-methylene proton (HA, HB) anisochrony than thetrans-forms; (ii) anisochrony, easily observed in certain decalin-10-carboxylic ethyl esters, ‘disappears’ on one of the rings attaining the possibility of transforming into a ‘twist’ form; (iii) in certain pairs of chiralsecethyl esters and theirtert-methylated analogues anisochrony is higher in the latter, contrary to expectation, while, in certain others, the reverse is observed. Attempted explanations are based on assessments whether H A and H B are or are not in highly different magnetic environments in confomers regarded as preferred. This subsumes the possibility thatXYZC-CO2H A H B Me chiral ethyl acetates differ fromXYZC-CH A H B Me ethanes because intervention by the carboxyl group insulates the prochiral centre and allows anisotropic effects to gain somewhat in importance among mechanisms that discriminate between H A and H B so long as rotamerpopulation inequalities persist. Background information on why rotamer-population inequalities will always persist and on a heuristic that attempts to generalize the effects ofXYZ inXYZC - CU AUB V is provided. Possible effects when connectivity exists between a pair amongX, Y, Z or when specific interactions occur betweenV andX, Y orZ are considered. An interpretation in terms of ‘increasing conformational mobility’ has been suggested for the observed increase in the rate of temperature-dependence of O-methylene anisochrony down a series of chiral ethyl esters.

Studies involving electrostatic potential of valinomycin

The electrostatic potential of valinomycin in various conformations as obtained by the crystal structures (uncomplexed, complexed) and theoretical considerations have been evaluated and compared. The potential energy profiles along the æ axis of the bracelet-like structures show a systematic variation from the uncomplexed to the complexed structure. This type of conformational change and the potential variation are probably associated with different states of ion transport, like the capture and release of ions by the ionophore. Also, the asymmetry of the molecule due to D-HyIV on one side and L-Lac on the other side is reflected in the potential values along the Z-axis, the magnitude of which, is considerable in the uncomplexed structure. The evaluation of the potential at the ab-initio level on smaller fragments indicate that the order of liganding capacity of oxygen is amide ether ester. Also, the inductive effects due to alkyl substitution is negligible as evidenced by the potential studies on the substituted amides and esters.

Contributions to organic synthesis and reaction mechanisms

Development of new methods, leading to the first stereo-specific total synthesis of a steroid,viz equilenin, and of estrone and their derivatives and of several important synthones, useful for the preparation of physiologically active steroids, and the first conversion of an equilenane to estrane have been described. An account of the achievement of original syntheses of testosterone and its isomers and derivatives and degradation products, urinary steroids, terpenes and their important degradation products has been given. Mechanisms of Dieckmann cyclization, a novel dehydrogenation-addition reaction involving abietic acid and tetrachloro-o-benzoquinone, a rearrangement involving a substitution of cyclopentanone-2-carboxylic ester have been elucidated. An abnormaluv absorption exhibited by saturated 1,2-dicyano esters has been rationalized. Divergences in theord data of testosterone and 19-nortesto-sterone from their isomers have been explained by x-ray crystallographic studies of 8-isotestosterone, 8-iso-10-isotestosterone and 8-iso-10-iso-19-nortestosterone. A tentative explanation for the difference in their physiological activities has been suggested.

Vitamin A economy of the developing chick embryo and of the freshly hatched chick

. The changes in the net amounts of retinol, retinyl esters and retinal in both the developing chick embryo and the newly hatched chick were investigated. The embryo requires about 68nmol of the vitamin for its growth, whereas the baby chick requires about 108nmol during the first 7 days after hatching. 2. Retinal was present in the egg in fairly high concentrations at the beginning of the incubation but it virtually disappeared from the extra-embryonic tissue after day 17 of incubation. It was not found in the liver of the embryo or of the newly hatched chick up until day 7.