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981.
Wienk HL Martínez MM Yalloway GN Schmidt JM Pérez C Rüterjans H Löhr F 《Journal of biomolecular NMR》2003,25(2):133-145
A quantitative J-correlation pulse sequence is described that allows simultaneous determination of one-bond and two-bond nitrogen-carbon coupling constants for protonated or deuterated proteins. Coupling constants are calculated from volume ratios between cross peaks and reference axial peaks observed in a single 3D spectrum. Accurate backbone 1
J
NC, 1
J
NC, and 2
J
NC coupling constants are obtained for the two [15N;13C]-labeled, medium-sized proteins flavodoxin and xylanase and for the [2H;15N;13C]-labeled, large protein DFPase. A dependence of one-bond and two-bond J
NC values on protein backbone torsion angles is readily apparent, in agreement with previously found correlations. In addition, the experiment is performed on isotropic as well as aligned protein to measure associated 15N-13C residual dipolar couplings. 相似文献
982.
Suwalsky M Hernández PL Villena F Sotomayor CP 《Zeitschrift für Naturforschung. C, Journal of biosciences》2003,58(11-12):885-890
Cytarabine, an analog of deoxycytidine, is an important agent in the treatment of ovarian carcinoma, acute myeloid and lymphoblastic leukemia. Its mechanism of action has been attributed to an interference with DNA replication. The plasma membrane has received increasing attention as a possible target of antitumor drugs, where the drugs may act as growth factor antagonists and receptor blockers, interfere with mitogenic signal transduction or exert direct cytotoxic effects. Furthermore, it has been reported that drugs that exert their antiproliferative effect by interacting with DNA generally cause structural and functional membrane alterations which may be essential for growth inhibition by these agents. This paper describes the studies undertaken to determine the structural effects induced by cytarabine to cell membranes. The results showed that cytarabine, at a concentration about one thousand times higher than that found in plasma when it is therapeutically administered, did not induce significant structural perturbation in any of these systems. Therefore, it can be unambiguously concluded that this widely used anticancer drug does not interact at all with erythrocyte membranes. 相似文献
983.
López-Marín LM Segura E Hermida-Escobedo C Lemassu A Salinas-Carmona MC 《FEMS immunology and medical microbiology》2003,36(1-2):47-54
Mycobacterial O-acyltrehaloses have been described as highly specific and sensitive reagents for tuberculosis immunodiagnosis. An O-acyltrehalose-containing lipid fraction from the rapidly growing Mycobacterium fortuitum was found to include additional antigens, which presented high cross-reactivity with sera from tuberculosis-infected patients. Based on a combination of selective chemical degradations, thin-layer-chromatography analyses and (1)H-nuclear magnetic resonance spectroscopy, the antigenic by-product was identified as 6,6'-dimycoloyl trehalose, the so-called cord factor. The lipid was purified and tested in ELISA for pulmonary tuberculosis serodiagnosis. Sensitivity and specificity of the test were found to be 66.6-74.1% and 95.2-99.0%, respectively, showing a slightly higher efficiency as compared to the ELISA performed using 6,6'-dimycoloyl trehalose from Mycobacterium tuberculosis. No cross-reactivity was found with sera from Nocardia-infected individuals. 相似文献
984.
Tubulin diversity in trophozoites of<Emphasis Type="Italic"> Giardia lamblia</Emphasis> 总被引:1,自引:0,他引:1
Campanati L Troester H Monteiro-Leal LH Spring H Trendelenburg MF de Souza W 《Histochemistry and cell biology》2003,119(4):323-331
Giardia lamblia is a diplomonad that parasitizes the small intestine of vertebrates. The trophozoite is multiflagellar and its cytoskeleton presents a complex organization of microtubular structures. One of these, the adhesive disk, consists of a microtubular spiral. The median body, whose function is not yet determined, is also composed by microtubules. The cell has eight flagella and two microtubule sheets, known as the funis. In this study we used several antibodies and immunofluorescence microscopy to help in the characterization of these structures. We observed that Giardia tubulin reacts with antibodies raised against very distinct immunogens. The antibodies used were against: (1) alpha-tubulin from chicken embryo brain, Trypanosoma brucei, sea urchin sperm, Paramecium, acetylated alpha-tubulin from Paramecium, and tyrosinated alpha-tubulin, (2) beta-tubulin from chicken embryo brain and Physarum polycephalum, and (3) an antibody with specificity to beta-tubulin having as immunogen the FtsZ bacterial protein. Each cytoskeletal structure of Giardia presented a distinct pattern of labeling by the several antibodies used. These data indicate that even being considered one of the most ancient of organisms, Giardia shares similarities (at least in relation to tubulin) with other organisms. They also open some questions about the organization and composition of its microtubular structures. 相似文献
985.
This work describes the long-term acclimation of the halotolerant microalga Dunaliella viridis to different photon irradiance, ranging from darkness to 1500 μmol m−2 s−1. In order to assess the effects of long-term photoinhibition, changes in oxygen production rate, pigment composition, xanthophyll
cycle and in vivo chlorophyll fluorescence using the saturating pulse method were measured. Growth rate was maximal at intermediate irradiance
(250 and 700 μmol m−2 s−1). The increase in growth irradiance from 700 to 1500 μmol m−2 s−1 did not lead to further significant changes in pigment composition or EPS, indicating saturation in the pigment response
to high light. Changes in Photosystem II optimum quantum yield (Fv/Fm) evidenced photoinhibition at 700 and especially at 1500 μmol m−2 s−1. The relation between photosynthetic electron flow rate and photosyntetic O2 evolution was linear for cultures in darkness shifting to curvilinear as growth irradiance increased, suggesting the interference
of the energy dissipation processes in oxygen evolution. Carbon assimilation efficiencies were studied in relation to changes
in growth rate, internal carbon and nitrogen composition, and organic carbon released to the external medium. All illuminated
cultures showed a high capability to maintain a C:N ratio between 6 and 7. The percentage of organic carbon released to the
external medium increased to its maximum under high irradiance (1500 μmol m−2 s−1). These results suggest that the release of organic carbon could act as a secondary dissipation process when the xanthophyll
cycle is saturated.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
986.
987.
The genomic organization and evolution of the natural killer immunoglobulin-like receptor (KIR) gene cluster 总被引:18,自引:7,他引:11
Natural killer (NK) immunoglobulin-like receptors (KIRs) are a family of polymorphic receptors which interact with specific
motifs on HLA class I molecules and modulate NK cytolytic activity. In this study, we analyzed a recently sequenced subgenomic
region on chromosome 19q13.4 containing eight members of the KIR receptor repertoire. Six members are clustered within a 100-kb continuous sequence. These genes include a previously unpublished
member of the KIR gene family 2DS6, as well as 2DL1, 2DL4, 3DL1, 2DS4, 3DL2, from centromere to telomere. Two additional KIR genes, KIRCI and 2DL3, which may be located centromeric of this cluster were also analyzed. We show that the KIR genes have undergone repeated gene duplications. Diversification between the genes has occurred postduplication primarily
as a result of retroelement indels and gene truncation. Using pre- and postduplication Alu sequences identified within these
genes as evolutionary molecular clocks, the evolution and duplication of this gene cluster is estimated to have occurred 30–45 million
years ago, during primate evolution. A proposed model of the duplication history of the KIR gene family leading to their present organization is presented.
Received: 25 November 1999 / Revised: 10 January 2000 相似文献
988.
Medeiros AB Pandey A Freitas RJ Christen P Soccol CR 《Biochemical Engineering Journal》2000,6(1):33-39
Studies were carried out for the production of aroma compounds in solid-state fermentation using factorial design and response surface methodology (RSM) experiments. Five agro-industrial residues were evaluated as substrate for cultivating a strain of Kluyveromyces marxianus. The results proved the feasibility of using cassava bagasse and giant palm bran (Opuntia ficus indica) as substrates to produce fruity aroma compounds by the yeast culture. In order to test the influence of the process parameters on the culture to produce volatile compounds, two statistical experimental designs were performed. The parameters studied were initial substrate pH, addition of glucose, cultivation temperature, initial substrate moisture and inoculum size. Using a 2(5) factorial design, addition of glucose and initial pH of the substrate was found statistically significant for aroma compounds production on palm bran. Although this experimental design showed that addition of glucose did not have a significant role with cassava bagasse, 2(2) factorial design revealed that glucose addition was significant at higher concentrations. Head-space analysis of the culture by gas chromatography showed the production of nine and eleven compounds from palm bran and cassava bagasse, respectively, which included alcohols, esters and aldehyde. In both the cases, two compounds remained unidentified and ethyl acetate, ethanol and acetaldehyde were the major compounds produced. Esters produced were responsible for the fruity aroma in both the cases. With palm bran, ethanol was the compound produced in highest concentration, and with cassava bagasse (both supplemented with 10% glucose), ethyl acetate was produced at highest concentration, accumulating 418 and 1395μmoll(-1) head-spaceg(-1) substrate in 72h, respectively. 相似文献
989.
Méndez AT Roig-López JL Santiago P Santiago C García-Arrarás JE 《Marine biotechnology (New York, N.Y.)》2000,2(3):231-240
The Echinodermata is a unique animal group forming an early branch in the deuterostomes phylogenetic tree. In echinoids and
asteroids a single Hox cluster with nine cognates of the vertebrate Hox paralogous groups has been reported, but no data are available from other echinoderm classes. We report here nine Hox-type sequences from the sea cucumber Holothuria glaberrima, a member of the class Holothuroidea. Partial homeodomain sequences were amplified by polymerase chain reaction from genomic
DNA and from a regenerating gastrointestinal tract complementary DNA library. Sequence analyses suggest that the holothuroid
cluster has at least three genes of the anterior, one of the medial, and five of the posterior groups. This is the first evidence
of five posterior sequences in echinoderms.
Received July 19, 1999; accepted October 18, 1999. 相似文献
990.
Association of the low-density lipoprotein receptor gene with obesity in Native American populations 总被引:3,自引:0,他引:3
Five low-density lipoprotein receptor gene (LDLR) restriction fragment length polymorphisms (RFLPs: TaqI, intron 4; HincII, exon 12; AvaII, exon 13; MspI and NcoI, exon 18) were investigated in 131 individuals from five Brazilian Indian tribes. All markers were polymorphic in this ethnic group. In the whole sample of Amerindians, 13 (41%) of the 32 expected haplotypes were identified, but only three were shared by all tribes. The Xavante, Suruí, Zoró, and Gavi?o tribes, who had been studied for anthropometry, were grouped according to their genotypes, and the corresponding mean values were examined. Significant associations were observed between HincII *H-, AvaII *A+, MspI *M-, and NcoI *N+ and the body mass index (BMI), triceps and subscapular skinfolds, and the arm fat index (AFI). Haplotypes were derived for these four RFLPs, and (*H-/*A+/*M-/*N+) haplotype carriers were compared with noncarriers of this haplotype with equally significant results for the three parameters (BMI, P=0.021; skinfold thickness, P<0.001; AFI, P=0.005). These results suggest that the LDLR gene has some influence over adipose tissue deposition. 相似文献