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81.
Meiofauna associated with a Pacific coral reef in Costa Rica 总被引:3,自引:0,他引:3
The meiofauna of two coral reef habitats at Isla del Naño, Costa Rica was studied over a one year period. The dominant groups were: Foraminifera (21.2%), Copepoda (19.7%), Nematoda (19.1%), Gastropoda (16.5%), Polychaeta (7.2%) and Bivalvia (6.6%). The highest diversity was found in coarse, heterogeneous sands with the highest percentage of carbonates. The meiofauna showed a high degree of horizontal aggregation, which is a characteristic pattern for macro- and meiofauna in sediments of variable composition. No vertical variation in distribution was evident, probably due to the deep location of the Redox Potential Discontinuity layer. The total densities of organisms found in this study (99 to 575 ind/10 cm2) are low compared with densities in similar non-reefal sands (7 to 6116), and from fine sediments (80 to 17 000), but are comparable to densities found in other reef areas (39 to 609.5 ind/10 cm2). This is the first report on meiofauna from the eastern Pacific, and the first time that foraminiferans are the dominant group. 相似文献
82.
Conformational predictive studies on the activation segment of pancreatic procarboxypeptidases 总被引:1,自引:0,他引:1
M Vilanova F X Avilés J Vendrell E Méndez 《Biochemical and biophysical research communications》1987,149(2):729-734
Little is known about the conformation and evolutionary origin of the activation segment of pancreatic procarboxypeptidases. Analysis of the sequence and secondary structure propensities of these propeptide segments indicate that they contain two regions structurally related to the Ca2+-binding sites of the EF-hand protein family. This proposed homology could explain how (and why) carboxypeptidases developed such long (94 residues) activation peptides. 相似文献
83.
C Domènech J Abante F X Bozal A Mazo A Cortés J Bozal 《Biochemical and biophysical research communications》1987,147(2):753-757
Different homogeneously purified cytosolic malate dehydrogenases gave, on isoelectric focusing, several active bands. The phenomenon could not be assigned to differences in their molecular weights or to alterations in the enzyme preparations during the purification procedure. Resolution of the multiple malate dehydrogenase active bands was achieved by chromatofocusing. The aged isolated subforms always yielded the original electrofocusing pattern. This fact suggests that conformational isomerism is a likely explanation for the charge heterogeneity of the enzymes studied. 相似文献
84.
Incorporation of the carbocyclic analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate into a synthetic DNA 总被引:1,自引:0,他引:1
J Sági E De Clercq A Szemz? A Csárnyi T Kovács L Otv?s 《Biochemical and biophysical research communications》1987,147(3):1105-1112
The carbocyclic analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine, C-BVDU, is a very potent and selective anti-herpes-virus compound. In order to synthesize and study the properties of a DNA that contains C-BVDU, the 5'-triphosphate, C-BVDUTP was prepared and evaluated as a potential substrate of the E. coli Klenow DNA polymerase enzyme. Although C-BVDUTP proved to be a very poor substrate also of this enzyme, it could be incorporated up to 3.6% into the synthetic DNA, poly(dA-dT, C-BVDU). This level of substitution decreased significantly the template activity for DNA and RNA polymerases, as compared to that of poly(dA-dT). 相似文献
85.
Isolation, purification and 1H-NMR characterization of a kringle 5 domain fragment from human plasminogen 总被引:2,自引:0,他引:2
A scheme is proposed for generating the intact Val-448-Phe-545 polypeptide of human plasminogen which contains the fifth kringle domain of the plasmin heavy chain. The procedure is based on a pepsin fragmentation of miniplasminogen and involves the purification of the kringle 5-containing fragment by gel filtration and ion-exchange chromatography. The final product is characterized by amino acid analysis, N- and C-terminal analyses, and high-resolution 1H-NMR spectroscopy at both 300 MHz and 611 MHz. We detect a (40:60%) Asp/Asn heterogeneity at site 452 of the Glu-plasminogen molecule. In the conventional kringle numbering system, the kringle 5 domain extends from Cys-1 to Cys-80, which corresponds to Cys-461 to Cys-540 in plasminogen. A preliminary 1H-NMR characterization of kringle 5 focuses on the global conformational features of the polypeptide. Assignments are given for a number of resonances, including the Tyr-72, the His imidazoles' and the Trp indoles' spin systems. Comparison with human plasminogen kringles 1 and 4 shows that the kringle 5 conformation is highly structured and very similar to that of the homologous domains. This conservancy is particularly striking in the environment surrounding Leu-46 and in the overall features of the aromatic spectrum. There are some differences, particularly in the buried His-33 imidazole group, whose H2 resonance is shifted to 9.67 ppm. A preliminary study of benzamidine-binding shows that the ligand interacts weakly (Ka approximately equal to 1.7 mM -1) mainly through the amidino functional group. Trp-62 and Tyr-72 are significantly perturbed by benzamidine, suggesting that these residues are part of the ligand-binding site. 相似文献
86.
Donald A. Gailey Deborah L. Bordne Ana Maria Vallés Jeffrey C. Hall Kalpana White 《Genetics》1987,115(2):305-311
An unstable Ring-X chromosome, Ddc+- Ring-X carrying a cloned Dopa decarboxylase (Ddc) encoding segment was constructed. The construction involved a double recombination event between the unstable Ring-X, R(1)wvC and a Rod-X chromosome which contained a P-element mediated Ddc + insert. The resulting Ddc+-Ring-X chromosome behaves similarly to the parent chromosome with respect to somatic instability. The Ddc+-Ring-X chromosome was used to generate Ddc mosaics. Analyses of Ddc mosaics revealed that while there was no absolute requirement for the Ddc + expression in either the epidermis or the nervous system, very large mutant clones did affect the viability of the mosaic. 相似文献
87.
88.
C Domènech X Bozal A Mazo A Cortés J Bozal 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,88(2):461-466
Malate dehydrogenases from several sources show different behaviour when frozen-thawed in 100 mM sodium phosphate buffer, pH 7.4, containing chaotropic ions. The effects produced by the addition of various metabolites, protein concentration and buffer medium used on the loss of activity induced by the freezing-thawing process are reported. The major part of the loss of activity is caused by the formation of "wrong" aggregates of high mol. wt. 相似文献
89.
Substrate specificity of DNA polymerases. I. Enzyme-catalysed incorporation of 5-''1-alkenyl)-2''-deoxyuridines into DNA. 总被引:2,自引:2,他引:0
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A series of (E)-5-(1-alkenyl)-dUTPs as well as 5-vinyl-and (Z)-5-(1-propenyl)-dUTP have been synthesized to study steric requirements in DNA polymerase reactions. Experiments were carried out in E. coli DNA polymerase I Klenow fragment enzyme system. Substrates were characterized by KM and Vmax-values, initial incorporation rates as well as by total extent of incorporation of the analogues into poly(dA-dT) as a template-primer. Incorporation of the analogues could be best correlated with Vmax-values as well as the very similar initial incorporation rate values. Reactivity (Vmax/KM) showed no correlation with the extent of incorporation. 5-Vinyl-dUTP proved to be as good a substrate of the enzyme as dTTP, whereas (E)-5-(1-heptenyl)-and (E)-5-(1-octenyl)-dUTPs were very poor substrates, their incorporation was strongly limited and they also proved to be very efficient inhibitors of DNA replication, as shown by Ki-values. Substrate specificity of the Klenow enzyme can be explained by the steric hindrance of C-5 substituent, by the "orientational steric substituent effect" concept. 相似文献
90.
Rosalina Pomés Concepción Gil M.D. Cabetas César Nombela 《FEMS microbiology letters》1987,48(1-2):255-259
Abstract Colonies of Candida albicans wild-type strain 1001 were white and glossy, and this character was rather stably maintained. In contrast, 2 benomyl (methyl benzimidazole-2-yl-carbamate)-induced mutant strains, B17 and B14, that grew as long filamentous forms and displayed a rough-wrinkled colonial phenotype, switched to other colonial morphologies at significant frequencies. Clonal populations of B17 segregated smooth or sectored (rough/smooth) colonies at a frequency of 1.85%, when plated in nutrient-agar. Strains derived from these rough or smooth segregants switched back to one or the other phenotype at similar frequencies. Colonial variability in C. albicans B14 was not restricted to spontaneous switching from rough to smooth or vice versa, but eventually other types of variants, characterized as 'wavy' and 'fuzzy' were obtained, and shown to have their own capacity to switch. Smooth variants, derived from B14, were essentiallt unicellular, whereas fuzzy strains consisted only of long thin filaments, wavy and rough clones apparently being intermediate in their degree of filamentation. It is concluded that the capacity for colonial variation shown to exist in natural isolates could be activated by benomyl in others, such as 1001, which are quite stable and do not switch colonial morphology spontaneously. 相似文献