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1.
Virginia Edgcomb William Orsi John Bunge Sunok Jeon Richard Christen Chesley Leslin Mark Holder Gordon T Taylor Paula Suarez Ramon Varela Slava Epstein 《The ISME journal》2011,5(8):1344-1356
Microbial diversity and distribution are topics of intensive research. In two companion papers in this issue, we describe the results of the Cariaco Microbial Observatory (Caribbean Sea, Venezuela). The Basin contains the largest body of marine anoxic water, and presents an opportunity to study protistan communities across biogeochemical gradients. In the first paper, we survey 18S ribosomal RNA (rRNA) gene sequence diversity using both Sanger- and pyrosequencing-based approaches, employing multiple PCR primers, and state-of-the-art statistical analyses to estimate microbial richness missed by the survey. Sampling the Basin at three stations, in two seasons, and at four depths with distinct biogeochemical regimes, we obtained the largest, and arguably the least biased collection of over 6000 nearly full-length protistan rRNA gene sequences from a given oceanographic regime to date, and over 80 000 pyrosequencing tags. These represent all major and many minor protistan taxa, at frequencies globally similar between the two sequence collections. This large data set provided, via the recently developed parametric modeling, the first statistically sound prediction of the total size of protistan richness in a large and varied environment, such as the Cariaco Basin: over 36 000 species, defined as almost full-length 18S rRNA gene sequence clusters sharing over 99% sequence homology. This richness is a small fraction of the grand total of known protists (over 100 000–500 000 species), suggesting a degree of protistan endemism. 相似文献
2.
3.
The genetic structure of six populations of Iran (Turks, Kurds, Lurs, Zabolis, Baluchis and Zoroastrians) was examined using
data on blood groups, serum proteins and cell enzymes. Our results show conclusively that there are genetic differences among
the six populations and the analysis of superimposed R and S matrices defined by Harpending & Jenkins (1973) show that the
dispersion of some of the alleles correspond to the dispersion of the populations. The FST estimates are not large enough to favour selection on any of the loci studied. The FIT and FIS estimates are positive and moderately high suggesting that the genetic differentiation to some extent is influenced by inbreeding. 相似文献
4.
L-Rhamnal was acylated under a variety of conditions with various acylating reagents. Substitution of the hydroxyl group in the allylic position was favored when acetyl chloride, N-acetylimidazole, benzoyl chloride, and N-benzoylimidazole were used (40-60% net yields), whereas the homoallylic group of L-rhamnal was selectively protected when acetic anhydride-pyridine was employed for the acylation. The monoacetates of L-fucal underwent O-3----O-4 migration of the acetyl group, and selective acylation of this glycal could not be achieved. 相似文献
5.
Phospholipid methyltransferase phosphorylation by intact hepatocytes: effect of glucagon 总被引:2,自引:0,他引:2
I Varela I Mérida M Villalba F Vivanco J M Mato 《Biochemical and biophysical research communications》1985,131(1):477-483
We have obtained a rabbit antiserum that specifically immunoprecipitates the 50K and 25K proteins of rat liver phospholipid methyltransferase. Exposure of intact rat hepatocytes preincubated with [32P]phosphate to glucagon induces a time-dependent phosphorylation of the 50K protein of phospholipid methyltransferase. The incorporation of 32P into the 50K protein was only on phosphoserine. These data support the concept that the activation of rat liver phospholipid methyltransferase by glucagon is mediated by phosphorylation of the enzyme. 相似文献
6.
Antonio Bode Benita Casas Emilio Fernández Emilio Marañón Pablo Serret Manuel Varela 《Hydrobiologia》1996,341(3):225-234
Summary Chlorophyll-a and primary production on the euphotic zone of the N-NW Spanish shelf were studied at 125 stations between 1984 and 1992. Three geographic areas (Cantabrian Sea, Rías Altas and Was Baixas), three bathymetric ranges (20 to 60 m, 60 to 150 m and stations deeper than 200 m), and four oceanographic stages (spring and autumn blooms, summer upwelling, summer stratification and winter mixing) were considered. One of the major sources of variability of chlorophyll and production data was season. Bloom and summer upwelling stages have equivalent mean and maximum values. Average chlorophyll-a concentrations approximately doubled in every step of the increasing productivity sequence: winter mixing — summer stratification — high productivity (upwelling and bloom) stages. Average primary production rates increased only 60% in the described sequence. Mean (± sd) values of chlorophyll-a and primary production rates during the high productivity stages were 59.7 ± 39.5 mg Chl-a m–2 and 86.9 ± 44.0 mg C m–2 h–1, respectively. Significant differences in both chlorophyll and primary production resulted between geographic areas in most stages. Only 27 stations showed the effects of the summer upwelling that affected coastal areas in the Cantabrian Sea and Rías Baixas shelf, but also shelf-break stations in the Rías Altas area. The Rías Baixas area had lower chlorophyll than both the Rías Altas and the Cantabrian Sea areas during spring and autumn blooms, but higher during summer upwelling events. On the contrary, primary production rates were higher in the Rías Baixas area during blooms in spring and autumn. Mid-shelf areas showed the highest chlorophyll concentrations during high productivity stages, probably due to the existence of frontal zones in all geographic areas considered. The estimated phytoplankton growth rates were comparable to those of other coastal upwelling systems, with average values lower than the maximum potential growth rates. Doubling rates for upwelling and stratification stages in the northern and Rías Altas shelf areas were equivalent, despite larger biomass accumulations during upwelling events. Low turnover rates of the existing biomass in the Rías Baixas shelf in upwelling stages suggests that the accumulation of phytoplankton was due mainly to the export from the highly productive rías, while the contribution of in situ production to these accumulations was relatively lower. 相似文献
7.
Oscar Varela Patricia A. Zunszain Daniel O. Cicero Ricardo F. Baggio Daniel R. Vega María T. Garland 《Carbohydrate research》1996,280(2):187
The conformation in 2H2O of 4-thio-l-lyxono-1,4-lactone (1) was studied by nuclear magnetic resonance spectroscopy, by means of homonuclear (J1H,1H) and heteronuclear (J1H,13C) coupling constants. The couplings were directly measured by a two-dimensional heteronucleus-coupled ω1 hetero-half-filtered proton-proton correlation (HETLOC) experiment, which does not require 13C isotopic enrichment. In solution, the thiolactone ring of 1 adopts preferentially the E3 conformation, and its hydroxymethyl group populates mainly the gt rotamer. The X-ray diffraction data of a single crystal of 1 indicates that also in the solid state the thiolactone ring adopts an E3 conformation, with a puckering somewhat larger than that observed for aldono-1,4-lactones and furanose rings. The molecules are linked by hydrogen bonds, which form chains. Particularly, O-5 is fully engaged as donor and acceptor in hydrogen bonding and the rotameric conformation of the hydroxymethyl group of 1 is fixed in the tg form. 相似文献
8.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
9.
10.
Pablo Morales Alfredo Corell Jorge Martínez-Laso J. Manuel Martín-Villa Pilar Varela Estela Paz-Artal Luis-M. Allende Antonio Arnaiz-Villena 《Immunogenetics》1993,38(5):323-331
Three new allelic forms of the HLA-G DNA sequence (HLA-G*II, HLA-G*III, and HLA-G*IV) have been identified. With the HLA-G*I sequence (previously designated HLA 6.0) as a reference, HLA-G*II shows a silent (G A) mutation at the third base of codon 57, HLA-G*III bears a non-synonymous (A T), but conservative, (Thr Ser) substitution at the first base of codon 31, and HLA-G*IV shows two silent substitutions: (A T) at the third base of codon 107 and (G A) at the third base of codon 57. A rapid method of singling out each allele on genomic DNA has been developed by using polymerase chain reaction amplification followed by restriction endonuclease treatment. Also, more or less strong linkage disequilibria has been found between most HLA-A alleles and either HLA-G*I or *II, both being the most prevalent alleles in the population, with a genotypic frequency of 0.55 and 0.38, respectively; HLA-G*III is very rare and HLA-G*IV has a genotypic frequency of 0.07. An evolutive classification of HLA-A alleles results according to their association with either HLA-G*I or HLA-G*II, which does not correlate with the classical serological cross-reacting groups classification. The finding of a strong and selective A/G linkage disequilibria with most HLA-A alleles, together with the existence of less frequent random A/G associations, may suggest that there exist in different haplotypes true and varied A/G genetic distances (and not a recombinational hotspot). It may be inferred from preliminary data that in primates HLA-A/G haplotypes bearing G*II may have appeared later than those bearing G*I.The nucleotide sequence data reported in this paper have been submitted to the GenBank and EMBL nucleotide sequence databases and have been assigned the following accession numbers: EMBL-X60983 (HLA-G*II), GenBank-M99048 (HLA-G*III), and GenBank-L07784 (HLA-G*IV).The contribution to this paper by P. Morales and A. Corell is equal, and the order of authorship is arbitrary.
Correspondence to: A. Arnaiz-Villena. 相似文献