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891.
Serguei Zoubak Giuseppe D'Onofrio Simone Cacciò Giacomo Bernardi Giorgio Bernardi 《Journal of molecular evolution》1995,40(3):293-307
All 69 homologous coding sequences that are currently available in four mammalian orders were aligned and the synonymous (ie., third) positions of quartet (fourfold degenerate) codons were divided into three classes (that will be called conserved, intermediate, and variable), according to whether they show no change, one change, and more than one change, respectively. The three classes were analyzed in their compositional patterns. In the majority of GC-rich genes, the three classes of positions (but especially conserved positions) exhibited significantly different base compositions compared to expectations based on a random substitution process from the ancestral (consensus) sequence to the present-day (actual) sequences. Significant differences were rare in GC-poor genes.An analysis of the present results indicates that natural selection plays a role in the synonymous nucleotide substitution process, especially in GC-rich genes which represent the vast majority of mammalian genes.This paper is dedicated to the memory of Dr. Motoo Kimura (1924–1994)Correspondence to: Giorgio Bernardi 相似文献
892.
Benedetto Di Blasio Michele Saviano Valerio Del Duca Giuseppina De Simone Filomena Rossi Carlo Pedone Ettore Benedetti Gian Paolo Lorenzi 《Biopolymers》1995,36(4):401-408
The x-ray diffraction analyses of three N- and C-terminally blocked L , D dipeptides, namely t-Boc-D -Leu-L -Leu-OMe ( 1 ), t-Boc-L -Ile-D -alle-OMe ( 2 ), and t-Boc-D -aIle-L -Ile-OMe (3) containing enantiomeric or diastereomeric amino acid residues have been carried out. The structures were determined by direct methods and refined anisotropically to final R factors of 0.077. 0.058. and 0.072 for ( 1 ) ( 2 ) and ( 3 ), respectively. Peptides 1–3 all assume a similar U-shaped structure with ? and ψ torsion angles cosrresponding to one of the possible calculated minimum energy regions (regions E and G for L residues, and F*. D* and H* for D residues). The peptide backbones of 1-3 are almost super-imposable [provided that the appropriate inversion of the chiral centers of ( 2 ) is made]. Side-chain conformations of Leu residues in peptide ( 1 ) are g? (tg?) for the L -Leu residue and the mirrored g+ (tg+) for the D -Leu residue; however, in peptides ( 2 ) and ( 3 ) the conformations of the isoconfiguralional side chains of the Ile or allo-Ile residues are (g?t) t and (tg+) tfor the L -Ile and the D -allo-Ile moieties, respectively. In all cases, these conformations correspond to the more populated conformers of β-branched residues statistically found in crystal structures of small peptides. The results seem to indicate that, at least in short peptides with enantiomeric or diastereoisomeric residues, the change in chirality in the main-chain atoms perturbs the backbone conformation to a lesser extent and the side chain conformation to a greater extent. © 1995 John Wiley & Sons, Inc. 相似文献
893.
Tania De Simone Ron S. Dickson Brian W. Skelton Allan H. White 《Inorganica chimica acta》1995,240(1-2):323-333
The phosphinoalkenes Ph2P(CH2)nCH=CH2 (n= 1, 2, 3) and phosphinoalkynes Ph2P(CH2)n C≡CR (R = H, N = 2, 3; R = CH3, N = 1) have been prepared and reacted with the dirhodium complex (η−C5H5)2Rh2(μ−CO) (μ−η2−CF3C2CF3). Six new complexes of the type (ν−C5H5)2(Rh2(CO) (μ−η1:η1−CF3C2CF3)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH3C5H4)Mn(CO)2thf resulted in coordination of the manganese to the alkene function. The Rh2---Mn complex [(η−C5H5)2Rh2(CO) (μ−η1:η1−CF3C2CF3) {Ph2P(CH2)3CH=CH2} (η−CH3C5H4)Mn(CO)2] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co2(CO)8 resulted in the coordination of Co2(CO)6 to the alkyne function. The Rh2---Co2 complex [(η−C5H5)2Rh2(CO) (μ−η1:η1−CF3C2CF3) {Ph2PCH2C≡CCH3}Co2(CO)2], C37H25Co2F6O7PRh2, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group
(Ci1, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on |F| was 0.052 fo observed (I > 3σ(I)) reflections. The Rh2 and Co2 parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh2 and perpendicular for Co2. Attempts to induce Rh2Co2 cluster formation were unsuccessful. 相似文献
894.
Jean-Franois Chich Pascal Rigolet Michle Nardi Jean-Claude Gripon Bruno Ribadeau-Dumas Simone Brunie 《Proteins》1995,23(2):278-281
The X-prolyl dipeptidyl aminopeptidase PepX, a serine peptidase isolated originally from Lactococcus lactis subsp lactis NCDO 763, was cloned and overproduced in Escherichia coli. The enzyme was isolated in its active form in two purification steps. Crystals of PepX were grown by the hanging drop vapor diffusion method using polyethyleneglycol 4000 as precipitant at pH 5.0. The crystals are orthorhombic with cell dimensions a = 92.8 Å, b = 102.6 Å, and c = 101.6 Å, space group P21212, and probably contain one monomer of 87.5 kDa in the asymmetric unit. The crystals, very stable under X-rays, diffract to at least 2.2 Å and are suitable for high-resolution structural analysis. © 1995 Wiley-Liss, Inc. 相似文献
895.
Martin Boissonneault Alcide Chapdelaine Simone Chevalier 《Molecular and cellular biochemistry》1995,147(1-2):139-144
The Na+–K+ ATPase activity and SH group content were decreased whereas malondialdehyde (MDA) content was increased upon treating the porcine cardiac sarcolemma with xanthine plus xanthine oxidase, which is known to generate superoxide and other oxyradicals. Superoxide dismutase either alone or in combination with catalase and mannitol fully prevented changes in SH group content but the xanthine plus xanthine oxidase-induced depression in Na+–K+ ATPase activity as well as increase in MDA content were prevented partially. The Lineweaver-Burk plot analysis of the data for Na+–K+ ATPase activity in the presence of different concentrations of MgATP or Na+ revealed that the xanthine plus xanthine oxidase-induced depression in the enzyme activity was associated with a decrease in Vmax and an increase in Km for MgATP; however, Ka value for Na+ was decreased. Treatment of sarcolemma with H2O2 plus Fe2+, an hydroxyl and other radical generating system, increased MDA content but decreased both Na+–K+ ATPase activity and SH group content; mannitol alone or in combination with catalase prevented changes in SH group content fully but the depression in Na+–K+ ATPase activity and increase in MDA content were prevented partially. The depression in the enzyme activity by H2O2 plus Fe2+ was associated with a decrease in Vmax and an increase in Km for MgATP. These results indicate that the depressant effect of xanthine plus xanthine oxidase on sarcolemmal Na+–K+ ATPase may be due to the formation of superoxide, hydroxyl and other radicals. Furthermore, the oxyradical-induced depression in Na+–K+ ATPase activity may be due to a decrease in the affinity of substrate in the sarcolemmal membrane. 相似文献
896.
897.
Simone A. French Robert W. Jejfery Aaron R. Folsom David F. Williamson Tim Byers 《Obesity (Silver Spring, Md.)》1995,3(2):163-170
FRENCH, SIMONE A, ROBERT W JEFFERY, AARON R FOLSOM, DAVID F WILLIAMSON AND TIM BYERS. History of intentional and unintentional weight loss in a population-based sample of women aged 55 to 69 years. Obes Res. 1995;3:163–170. Although both overweight and body weight fluctuation are related to chronic disease risk, little is known about the history of and reasons for body weight change in the general population. This paper reports the incidence of intentional and unintentional weight loss episodes during adulthood in a population-based sample of 26, 261 women aged 55 to 69 years. Intentional weight loss episodes of each of four amounts (5–9, 10–19, 20–49, 50+ lbs.) and unintentional weight loss episodes of 20 or more lbs. were recalled for each of three age periods (18–39, 40–54, 55+ years). At least one intentional weight loss episode of 5 or more lbs. was reported by 69% of women, 46% reported at least one intentional weight loss episode of 10 or more lbs, and 25% reported at least one intentional weight loss episode 20 or more lbs. At least one unintentional weight loss episode of 20 or more lbs. was reported by 29% of the women. Reasons for weight losses of 20 or more lbs. were also recalled. Women who had intentionally lost 20 or more lbs. were more likely to report weight losses due to low-calorie diets, exercise and weight loss groups, while women who had unintentionally lost 20 or more lbs. were more likely to report weight losses due to depression or stress. These findings question the common assumption that weight losses in adult women are primarily intentional and emphasize the need to distinguish the reasons for weight loss in studies examining the relationship between body weight changes and health outcomes. 相似文献
898.
A first linkage map of Cichorium intybus L. using a one-way pseudo-testcross and PCR-derived markers
De Simone Matteo Morgante Michele Lucchin Margherita Parrini Paolo Marocco Adriano 《Molecular breeding : new strategies in plant improvement》1997,3(6):415-425
We have used a one-way pseudo-testcross mapping strategy in combination with different types of PCR-based markers (RAPD, AFLP, SAMPL) to construct a first linkage map for variegated chicory (Cichorium intybus L. var. silvestre Biskoff, n=9), a self-incompatible vegetable species. The success of such a strategy depends on the presence of sufficiently high levels of heterozygosity in the individual plant which is being mapped and on the informativeness of the marker system that is used. A total of 371 markers, comprising 16 RAPDs, 72 SAMPLs and 283 AFLPs, were scored in 46 F1 individuals obtained from an interspecific cross between a C. intybus outbred individual and a C. endivia inbred line. Grouping of the markers at a LOD score of 4.0 resulted in 13 linkage groups covering 1330 cM. A framework map covering 1201.4 cM was assembled by using all markers that could be ordered with a LOD greater than 2.0. We estimate the total genome size of chicory to be ca. 1405 cM, thus considerably smaller than that estimated for lettuce (1950 cM). The usefulness of the different marker systems that were applied is analysed in terms of level of heterozygosity and marker index, i.e. number of different genetic loci that may be simultaneously analysed per experiment. Out of the 371 markers, 50 of them showed segregation distortion which is discussed in terms of the hybrid origin of the variegated chicory. 相似文献
899.
Simone Beck Farah Badbanchi Michael Otto Nicola Grzeschik Jürgen Kunz Norbert Speich Manfred Gessler Karl-Heinz Grzeschik 《Human genetics》1996,97(6):842-844
We report the isolation and characterization of six new polymorphic dinucleotide repeat microsatellite markers (D7S1491,
D7S1492, D7S1493, D7S1494, D7S1495, and D7S1496), their integration into the genetic map of human chromosome 7 by analysis
of 40 CEPH (Centre d’Etude du Polymorphisme Humain) pedigrees, and their use for integration of physical and genetic maps
of this chromosome.
Received: 14 September 1995 / Revised: 23 December 1995 相似文献
900.
Variable expression and geographic distribution of Mycoplasma agalactiae surface epitopes demonstrated with monoclonal antibodies 总被引:1,自引:0,他引:1
Dominique Bergonier Franco de Simone Pierre Russo Michel Solsona Maurice Lambert François Poumarat 《FEMS microbiology letters》1996,143(2-3):159-165
Abstract Species-speciGc monoclonal antibodies (MAbs) were developed against Mycoplasma agalactiae reference strain PG2 and French isolate P89 to study the in vitro expression of surface epitopes and to probe the antigenic profiles of 245 field isolates originating from 10 different countries. Colony immunostaining with MAbs on clonal lineage showed that 4 out of 9 species-specific epitopes exhibited a high rate of variation, demonstrating that M. agalactiae possesses a capacity for phenotypic diversification of its surface antigenicity. The emphasis was on dot immunobinding screening of the field isolates with MAbs recognizing permanently expressed epitopes. Eight different profiles could be defined. Great differences in epitope conservation were demonstrated with some area-specific strains completely lacking certain specific determinants. These results indicate that the antigenic variability of M. agalactiae relies not only upon surface switching mechanisms but also upon true epitope differences, partially related to the geographic origin of the isolates. 相似文献