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311.
312.
Adenylate cyclase from rabbit ventricle was solubilized in 30 to 50% yield by the nonionic detergent Lubrol PX. The detergent, when present in the assay at concentrations above 0.05%, rapidly inactivated the enzyme in assays conducted above 26 °C; assays were valid only when conducted below this temperature. The solubilized enzyme was eluted from diethylaminoethyl (DEAE)-Bio-Gel A (DEAE-agarose) with 100 mm NaCl in a yield of 25% and was free of detergent. Several properties of the solubilized detergent-free enzyme were similar to properties of the native membrane-bound species. The Km for substrate was 0.1 mm, the Ka for Mg2+ was 2.5 mm, and ATP in excess of Mg2+ was inhibitory. The enzyme was activated by F? and guanyl-5′-yl imidodiphosphate [Gpp(NH)p] in a time- and temperature-dependent manner, and activation by the latter was persistent. Activation by F? and Gpp(NH)p reduced the Ka for Mg2+. Activation by Gpp(NH)p was increased by Mg2+; the apparent Ka for activation was 0.1 μm. Multiple binding sites for Gpp(NH)p were present: one class with a Kd value of 0.11 μm was probably associated with activation of the enzyme. The soluble enzyme was insensitive to catecholamines, in both the presence and the absence of Gpp(NH)p. Sensitivity to catecholamines was not restored by the addition of phospholipids, particularly phosphatidyl inositol, in either the presence or the absence of Gpp(NH)p, and this phospholipid did not increase the sensitivity of the membrane-bound enzyme to epinephrine. Catecholamine binding sites were present, and their association with adenylate cyclase was seemingly not affected by phospholipids. 相似文献
313.
Infrared spectroscopy and 1H nmr have been used to elucidate the association modes of leucine dipeptides in carbon tetrachloride solution. Two stereoselective types of aggregates have been evidenced. Homochiral molecules are associated in oligomeric aggregates and accommodate a β-parallel-like structure which was characterized by x-ray diffraction. Heterochiral molecules are paired in centrosymmetrical dimers; the latter aggregation mode restricted to the dimer stage predominates in racemic solutions. A theoretical model proposed to account for this aggregation process is consistent with the experimental nmr data. Both homo- and heterochiral association constants are estimated from vapor pressure and nmr experiments. 相似文献
314.
315.
Jean Gaudant 《Geobios》1978,11(6):913-919
The revision of the fish fauna from the Messinian marls of Senigallia (Marche, Italy) leads to the reduction of the faunal list of the fossil Fishes found in this locality to only four species. One new genus is created: Cryptolebias new. gen.. This fish fauna characterizes an environment with a variable salt content: it may have been more or less temporarily connected with the sea, although it was also exposed to noticeable continental influences, as demonstrated by the occurrence of Amphibians and Reptiles (Ophidians). 相似文献
316.
John Blamire Corinne A. Michels Jean M. Walsh Debra L. Friedenberg 《Molecular & general genetics : MGG》1976,143(3):253-259
Summary The fluorinated pyrimidines 5-fluorouracil (5FU) and 5-fluorocytosine (5FC) induce the cytoplasmic petite mutation in the yeastSaccharomyces cerevisiae with high efficiency. It was found that in order to induce the mutation, 5FC must first be deaminated to 5FU. However, mutagenesis does not depend on the further conversion of 5FU to its deoxyriboside (5FUDR) and subsequent blockade of intracellular thymidine synthesis, since 5FUDR itself was found not to be mutagenic, and 5FU-induced mutagenesis was not antagonised by supplying thymidine monophosphate (dTMP) to a dTMP permeable strain. In any case, observations of the molecular changes accompanying petite induction in log phase cells ruled out the possibility that mutagenesis resulted simply from the dilution out of replication-blocked mitDNA molecules, since the appearance of mutants coincided with the synthesis of altered mitDNA molecules. In different strains, the resulting defective molecules were either maintained, giving rise to suppressive
– petites, or completely degraded, to give pure clones of neutral
0 mutants. It is suggested that this degradative process was a consequence of the incorporation of 5FU into RNA. 相似文献
317.
André Welter Joseph Jadot Gaston Dardenne Michel Marlier Jean Casimir 《Phytochemistry》1976,15(5):747-749
A new natural imino-alcohol, 2,5-dihydroxymethyl 3,4-dihydroxypyrrolidine has been isolated from the leaves of Derris elliptica. Its structure was determined by chemical and physical methods. 相似文献
318.
Anne-Marie Chevolot-Magueur Adrien Cave Pierre Potier Jean Teste Angèle Chiaroni Claude Riche 《Phytochemistry》1976,15(5):767-771
Four aromatic bromo compounds have been isolated from the ethanolic extract of Rytiphlea tinctoria after treatment with diazomethane: 2,4-dibromo-1,3,5-trimethoxy-benzene,5,6,3′,5′-tetrabromo-3,4,2′,4′,6′-pentamethoxydiphenylmethane, 5,6-dibromo-3,4-dimethoxy-benzyl alcohol and its ethyl ether. In addition to sterols, amino acids, this extract also contains quinonoid bromo-pigments which could play a rôle in photosensitisation of chlorophylls, a rôle normally taken by the phycobilins, in other Rhodophyceae. 相似文献
319.
Leaf pocket resins of 11 species of the tropical arborescent genus Hymenaea are virtually identical qualitatively, but of widely varying quantitative proportions. Within this large range of variability, several strong positive quantitative correlations between resin constituents were found, especially between caryophyllene and β-humulene and between γ-muurolene and δ-cadinene. These data lead to clarification of sesquiterpene biosynthetic routes in Hymenaea. In addition, quantitative relationships found among caryophyllene, α- and β-selinene, γ-muurolene and δ-cadinene are explained only with difficulty by long accepted biosynthetic pathways, and the intermediacy of germacrenes is suggested. 相似文献
320.
Antibodies against Lubrol-solubilized Electrophorus electroplax (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) and its 96 000-dalton polypeptide (P96) were raised in rabbits. The P96 antibody does not cross react with the (Na+ + K+)-ATPase from mammalian species and tissues, but it cross reacts with the (Na+ + K+)-ATPase from both Electrophorus electroplax and brain. The combination of enzyme with anti-P96 is found to inhibit phosphoryl enzyme formation to the same extent that it inhibits enzyme activity. The rate of K+-sensitive dephosphorylation of phosphoryl enzyme appears to be unchanged. These are also found to be true with the antibody against the whole enzyme. Upon tryptic digestion of the enzyme-anti-P96 complex only the large polypeptide of the enzyme is protected. In the case of enzyme-anti-Lubrol-solubilized enzyme complex, both the large and small polypeptides are protected, whereas preimmune sera are without any protecting effect. The data indicate that the phosphoryl acceptor polypeptide and the Lubrol-solubilized electroplax (Na+ + K+)-ATPase from which the polypeptide is derived are phylogenetically distinct from those of the mammalian (Na+ + K+)-ATPases. The selective tryptic resistance of the enzyme-anti-P96 complex indicates that the two polypeptides are spatially well separated, possibly on opposite sides of the membrane. 相似文献