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101.
Myriam Calonje Concepción García Mendoza Amelia Pérez Cabo Monique Novaes-Ledieu 《Current microbiology》1995,30(2):111-115
Significant differences in gross wall chemical composition were detected in four commercial Agaricus bisporus strains. All were grown under the same conditions and their walls prepared by a mild method of breakage. A more detailed analysis of the wall fractions, isolated by means of their distinct solubilities, also showed striking structural differences among the four strains studied. The detected differences, not only in the overall composition of the wall but also in the polysaccharide structure, could assist in the characterization of strains and/or varieties of the commercial basidiomycete A. bisporus. 相似文献
102.
M. Teresa García-López Ibon Alkorta M. José Domínguez Rosario González-Mu?iz Rosario Herranz Nils L. Johansen Kjeld Madsen Henning Th?gersen Peter Suzdak 《Letters in Peptide Science》1995,1(6):269-276
Summary In order to enforce different spatial orientations in the C-terminal hexapeptide of neurotensin (NT8–13) and to gain information about the importance of the 10–11 peptide bond for binding to NT receptors, the Pro10-Tyr11 fragment has been replaced with (2R,8S,8aR)-, (2S,8S,8aR)-, (2S,8S,8aS)-, (2S,8R,8aS)- and (2R,8R,8aS)-8-amino-2-benzyl-3-oxoindolizidine-2-carboxylic acid. Molecular dynamics calculations and energy minimization studies have shown that, contrarily to the Pro-Tyr moiety, none of these indolizidines display a tendency to adopt type I and III -turns, but those having (8S,8aR) or (8R,8aS) stereochemistry essentially adopt extended conformations and the (8S,8aS) stereoisomer prefers a nonstandard folding. The four diastereomeric NT8–13 analogues incorporating (8S,8aR) or (8R,8aS) indolizidines displayed binding affinities for the brain NT receptor similar to that of [Ala11]-NT8–13 and only five- to ninefold lower than that of the corresponding analogue, [Phe11]NT8–13. Although this slight decrease could be attributed to differences in conformational behavior between these constrained NT8–13 analogues and [Phe11]NT8–13 or NT8–13, it is not clear whether the -turn around Pro10-AA11 (AA=Phe, Tyr) is conserved upon receptor binding. An excessive restriction in the motions of the aromatic side chain, imposed by the highly steric constraint of the indolizidine moiety, emerges as an alternative explanation. The findings reported here demonstrate the possibility of replacing the Pro10-Tyr11 dipeptide in NT8–13 with a non-peptide residue without affecting considerably the affinity for brain NT receptors. 相似文献
103.
The interactions between reducing agents and Ca2+ in the activation of Ca2+-dependent K+ transport have been studied in one-step inside-out vesicles. The artificial electron donor system ascorbate + phenazine methosulphate increases the apparent sensitivity to Ca2+ by about 5-times over control values (half activation constant, about 5 X 10(-8) M) while oxidized cytochrome c decreases the sensitivity to about 1/3 of the controls. Using redox buffers at a fixed pCa it is shown that the shift from the low to the high-affinity state can be accounted by the reduction of a membrane component accepting two electrons and with an apparent standard redox potential (pH 7.5) of 47 mV. The electrons can be transferred directly from reduced PMS or to oxidized cytochrome c, but not from ascorbate, NADH or reduced glutathione. 相似文献
104.
The antilipolytic activity of a series of N aryl-nicotinamides and of alpha picolinic acid, has been tested in vitro. Lipolysis was stimulated by epinephrine (20 micrograms/ml of incubation medium) using rat's epididymal adipose tissue slices. Only N(2-carboxy methyl phenyl) nicotinamide showed antilipolytic effect comparable to that of nicotinic acid at similar concentrations (2 X 10(-5) M). Picolinic acid (10(-4) M) showed no antilipolytic effect. These results, together with those of the literature, are discussed in regard to the relations between structure and antilipolytic activity. 相似文献
105.
T Fontela O García-Hermida M C García-Fernández J Gómez-Acebo 《Revista Espanola de Fisiología》1984,40(1):77-81
The incorporation of glucose into glycogen was determined in pancreatic islets isolated from normal rats and incubated with glucose (5 or 20 mM) and compounds known to affect glycogen metabolism in other tissues. Incubation of pancreatic islets with glucose (20 mM) induced a marked increase in radioactive glycogen. Exposure to epinephrine in the presence of glucose (20 mM) slightly increased incorporation of glucose into glycogen. In contrast the incorporation of glucose into glycogen was not affected when isolated islets were exposed to glucagon or insulin, whereas anti-insulin serum in the incubation medium decreased radioactive glycogen formation. 相似文献
106.
M Saceda P García-Morales J M Mato W J Malaisse I Valverde 《Biochemistry international》1984,8(3):445-452
Glucose provokes a transient stimulation of phospholipid methylation in rat pancreatic islets, possibly by increasing phospholipid methyltransferase activity. The association of DL-homocysteine and 3-deazaadenosine inhibits phospholipid methylation. The methylation of phospholipids may play a role in the stimulus-secretion coupling for glucose-induced insulin release. 相似文献
107.
108.
From the aerial part of Teucrium chamaedrys a new neo-clerodane diterpenoid, dihydroteugin, has been isolated, besides the previously known diterpenoids teucrin A and teugin. The structure of dihydroteugin, (12S)-15,16-epoxy-2β,6β-dihydroxy-neo-cleroda-13(16), 14-diene-18,19:20,12-diolide, was established by chemical and spectroscopic means and by partial synthesis from teugin. 相似文献
109.
Osvaldo Mutchinick Lizbeth Ruz María E. Gonsebatt Patricia Mauleón Rubén Lisker Guillermo García 《Human genetics》1981,59(2):137-140
Summary Induced and spontaneous structural chromosome aberrations (SCA) were studied in a child accidentally radiated with a high dose of 192Ir, and in three sibs with Fanconi's anemia, analyzing by separate first division metaphases (FDM) and second division metaphases (SDM). The results showed that the number of SCA, number of cells with aberrations, and SCA per cell were markedly higher in FDM in all patients.Furthermore, for some type of structural changes like dicentric chromosomes and chromatid interchanges, the differences were particularly striking. The importance of ascertaining FDM identified with proper techniques, for the study of the clastogenic effect of environmental agents and some aspects related to the differences in cytogenetic features found in diverse tissues in Fanconi's anemia are discussed. 相似文献
110.
Mevalonate phosphorylation was studied in neonatal chick brain. Formation of phosphorylated derivatives of mevalonic acid increased with the pH in the range assayed (5.5–9.5). Phosphomevalonate kinase was completely inactivated after treatment at 50°C for 5–10 min, whereas mevalonate kinase was found to retain its activity under the same conditions. Exposure to 65°C for 5 min resulted in the inactivation of mevalonate kinase. Both mevalonate-activating enzymes from chick brain were located primarily in the soluble fraction. The amounts of phosphomevalonic acid and pyrophosphomevalonic acid did not show a significant diurnal variation to suggest the presence of a circadian rhythm in either kinase. Cholesterol feeding and fasting had no effect on mevalonate phosphorylation by neonatal chick brain. 相似文献