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61.
Oritavancin exhibits dual mode of action to inhibit cell-wall biosynthesis in Staphylococcus aureus 总被引:1,自引:0,他引:1
Kim SJ Cegelski L Stueber D Singh M Dietrich E Tanaka KS Parr TR Far AR Schaefer J 《Journal of molecular biology》2008,377(1):281-293
Solid-state NMR measurements performed on intact whole cells of Staphylococcus aureus labeled selectively in vivo have established that des-N-methylleucyl oritavancin (which has antimicrobial activity) binds to the cell-wall peptidoglycan, even though removal of the terminal N-methylleucyl residue destroys the d-Ala-d-Ala binding pocket. By contrast, the des-N-methylleucyl form of vancomycin (which has no antimicrobial activity) does not bind to the cell wall. Solid-state NMR has also determined that oritavancin and vancomycin are comparable inhibitors of transglycosylation, but that oritavancin is a more potent inhibitor of transpeptidation. This combination of effects on cell-wall binding and biosynthesis is interpreted in terms of a recent proposal that oritavancin-like glycopeptides have two cell-wall binding sites: the well-known peptidoglycan d-Ala-d-Ala pentapeptide stem terminus and the pentaglycyl bridging segment. The resulting dual mode of action provides a structural framework for coordinated cell-wall assembly that accounts for the enhanced potency of oritavancin and oritavancin-like analogues against vancomycin-resistant organisms. 相似文献
62.
Mounawer Badri Adel Zitoun Houcine Ilahi Thierry Huguet Mohamed Elarbi Aouani 《Journal of genetics》2008,87(3):241-255
Genetic variability in 10 natural Tunisian populations of Medicago laciniata were analysed using 19 quantitative traits and 12 polymorphic microsatellite loci. A large degree of genetic variability
within-populations and among-populations was detected for both quantitative characters and molecular markers. High genetic
differentiation among populations for quantitative traits was seen, with Q
ST
= 0.47, and F
ST
= 0.47 for microsatellite markers. Several quantitative traits displayed no statistical difference in the levels of Q
ST
and F
ST
. Further, significant correlations between quantitative traits and eco-geographical factors suggest that divergence in the
traits among populations may track environmental differences. There was no significant correlation between genetic variability
at quantitative traits and microsatellite markers within populations. The site-of-origin of eco-geographical factors explain
between 18.13% and 23.40% of genetic variance among populations at quantitative traits and microsatellite markers, respectively.
The environmental factors that most influence variation in measured traits among populations are assimilated phosphorus (P205) and mean annual rainfall, followed by climate and soil texture, altitude and organic matter. Significant associations between
eco-geographical factors and gene diversity, H
e
, were established in five-microsatellite loci suggesting that these simple sequence repeats (SSRs) are not necessarily biologically
neutral. 相似文献
63.
Mounawer Badri Adel Zitoun Sameh Soula Houcine Ilahi Thierry Huguet Mohamed Elarbi Aouani 《Conservation Genetics》2008,9(6):1509-1520
In this paper, we analyze the genetic variability in four Tunisian natural populations of Medicago ciliaris using 19 quantitative traits and six polymorphic microsatellite loci. We investigated the amplification transferability of
30 microsatellites developed in the model legume M. truncatula to M. ciliaris. Results revealed that about 56.66% of analyzed markers are valuable genetic markers for M. ciliaris. The most genetic diversity at quantitative traits and microsatellite loci was found to occur within populations (>80%).
Low differentiations among populations at quantitative traits Q
ST
= 0.146 and molecular markers F
ST
= 0.18 were found. The majority of measured traits exhibited no significant difference in the level of Q
ST
and F
ST
. Furthermore, significant correlations established between these traits and eco-geographical factors suggested that natural
selection should be invoked to explain the level of phenotypic divergence among populations rather than drift. There was no
significant correlation between population differentiation at quantitative traits and molecular markers. Significant spatial
genetic structure consistent with models of isolation by distance was detected within all studied populations. The site-of-origin
environmental factors explain about 9.07% of total phenotypic genetic variation among populations. The eco-geographical factors
that influence more the variation of measured traits among populations are the soil texture and altitude. Nevertheless, there
were no consistent pattern of associations between gene diversity (He) and environmental factors. 相似文献
64.
Robert W. Evans Roozina Rafique Adel Zarea Chiara Rapisarda Richard Cammack Patricia J. Evans John B. Porter Robert C. Hider 《Journal of biological inorganic chemistry》2008,13(1):57-74
Despite its importance in iron-overload diseases, little is known about the composition of plasma non-transferrin-bound iron
(NTBI). Using 30-kDa ultrafiltration, plasma from thalassemic patients consisted of both filterable and non-filterable NTBI,
the filterable fraction representing less than 10% NTBI. Low filterability could result from protein binding or NTBI species
exceeding 30 kDa. The properties of iron citrate and its interaction with albumin were therefore investigated, as these represent
likely NTBI species. Iron permeated 5- or 12-kDa ultrafiltration units completely when complexes were freshly prepared and
citrate exceeded iron by tenfold, whereas with 30-kDa ultrafiltration units, permeation approached 100% at all molar ratios.
A g = 4.3 electron paramagnetic resonance signal, characteristic of mononuclear iron, was detectable only with iron-to-citrate
ratios above 1:100. The ability of both desferrioxamine and 1,2-dimethyl-3-hydroxypyridin-4-one to chelate iron in iron citrate
complexes also increased with increasing ratios of citrate to iron. Incremental molar excesses of citrate thus favour the
progressive appearance of chelatable lower molecular weight iron oligomers, dimers and ultimately monomers. Filtration of
iron citrate in the presence of albumin showed substantial binding to albumin across a wide range of iron-to-citrate ratios
and also increased accessibility of iron to chelators, reflecting a shift towards smaller oligomeric species. However, in
vitro experiments using immunodepletion or absorption of albumin to Cibacron blue–Sepharose indicate that iron is only loosely
bound in iron citrate–albumin complexes and that NTBI is unlikely to be albumin-bound to any significant extent in thalassemic
sera. 相似文献
65.
66.
Mohammed Ramdani Roger J. Flower Najat Elkhiati with contributions from Hilary H. Birks Mohammed M. Kraïem Adel A. Fathi 《Aquatic Ecology》2001,35(3-4):389-403
Palaeolimnological studies were carried out on sediment cores from nine North African wetland lakes. The lakes represented a variety of habitats ranging from freshwater to mixohaline conditions and with and without direct connections to the sea. Sediment cores were examined for records of recent environmental change during the 20th century period. Faunal remains analysed in the sediments included those of Cladocera, Ostracoda, Chironomidae, Mollusca and, at the sites with marine connections, Foraminifera.
Cyprideis
torosa littoralis was the most common ostracod, occurring in sediments from the seven sites linked with the sea and also in brackish water Sidi Bou Rhaba. In acid Megene Chitane ostracods were scarce, being represented by a single species (Cypria ophtalmica).
Candona neglecta completely disappeared at two sites (Sidi Bou Rhaba and Bokka) during the 20th century. Of the Cladocera, Chydorus sphaericus was common in the moderately mixohaline sites and but Heterocypris salina occurred only where marine salinities were occasionally achieved (in Zerga, Ichkeul and Korba). Microinvertebrate assemblages in the Nile Delta lake cores and to a less extent in Zerga showed a clear response indicative of more fresher conditions occurring during the latter part of the 20th century. However the freshening trend began prior to construction of the Aswan High Dam (mid 1960s).With the exception of the most saline site (Korba), microinvertebrate communiuties at all the CASSARINA sites have experienced major disturbances during the 20th century. Changes in freshwater availability associated with increased human usage of water resources is perceived as a major factor regulating the abundance and occurrence of aquatic microinvertebrate species at these sites 相似文献
67.
Adel A. Basyouny Shahin 《Acta theriologica》2003,48(3):309-324
Genetic differentiation among 14 populations representing all Egyptian dipodid (jerboa) species and subspecies was examined at 25 structural loci and interspecific relationships are discussed. Of the 25 loci, only 3 were monomorphic, with the same allele fixed in all taxa, 9 loci were monomorphic, but demonstrated intertaxon variation, and only 13 loci were polymorphic. The overall mean number of alleles per locus (A) was 1.23 ± 0.02 and the average percentage of polymorphic loci per taxon (P) was 23%. The overall mean of observed heterozygosity (H o) was found significantly higher than that of expected heterozygosity (He); the overall means per taxon were 0.25 ± 0.017 and 0.085 ± 0.007. Mean levels of genetic identity (I) were 0.970 ± 0.003 among geographic populations, 0.718 ± 0.022 between subspecies, 0.590 ± 0.030 between congeneric species, and 0.368 ± 0.020 between genera. Phenetic analysis of genetic distance matrix produced a phenogram indicating a close association ofJaculus orientalis Erxleben, 1777 toJaculus jaculus (Linnaeus, 1758), particularly to its subspeciesJaculus jaculus butleri (Thomas, 1922), and indicating a distinct affinity between these latter two species andAllactaga tetradactyla (Lichtenstein, 1823). Estimates of genetic divergence demonstrated that J. orientalis appears to have shared a more recent common ancestor withJ. jaculus thanA. tetradactyla. Divergence of these species would have occurred by Miocene (ca 9.6 to 18.7 million years ago). The pattern of relationships of the dipodid species indicated in this study was closely consistent with the hypotheses derived from morphological and chromosomal data. 相似文献
68.
El-Faham Ayman El Massry Abdel Moneim Amer Adel Gohar Yousry M. 《International journal of peptide research and therapeutics》2002,9(1):49-54
Summary The synthesis ofN-protected L-amino acid (3-benzylquinoxalin-2-yl) hydrazide derivatives is reported here. 3-Benzyl-2-hydrazinoquinoxaline
was prepared and then coupled withN-Boc-L-amino acids including; Alanine, Valine, Leucine, Phenylalanine, Tyrosine, Serine and Proline in the presence of HBTU
as a coupling reagent to provide the expected product with high yield and purity. The products were deprotected by p-toluenesulphonic
acid in acetonitrile and then the tosylate salts were evaluated for antibacterial and antifungal activity.
Abbreviations: HBTU, N-[(1H-benzotriazol-1-yl)(dimethylamino)methylene]-N-methylmethanaminium hexafluorophosphate N-oxide Boc,t-butyloxycarbonyl, DIEA, diisopropylethylamine; DMF, N,N-dimethylformamide; PTSA, p-toluenesulphonic acid, TEA, triethyl amine.
Amino acids are abbreviated and designated following the rules of the IUPAC-IUB Commission of BiochemicalNomenclature (J. Biol. Chem., 247 (1972) 977). 相似文献
69.
Localization of urotensin-II immunoreactivity in normal human kidneys and renal carcinoma. 总被引:3,自引:0,他引:3
Andre Shenouda Stephen A Douglas Eliot H Ohlstein Adel Giaid 《The journal of histochemistry and cytochemistry》2002,50(7):885-889
Human urotensin-II (U-II) is a cyclic 11-amino-acid residue peptide with a wide range of vasoactive properties dependent on the anatomic site and the species studied. The purpose of this study was to determine the localization of human U-II in normal human kidneys and in renal carcinoma. Normal human kidneys (n=11) and eight cases of clear-cell carcinoma were immunostained with a polyclonal antibody to human U-II. In normal human kidneys, U-II was mostly present in the epithelial cells of tubules and ducts, with greater intensity in the distal convoluted tubules. Moderate U-II immunoreactivity was seen in the endothelial cells of renal capillaries, but only focal immunoreactivity was found in the endothelial cells of the glomeruli. No staining was found in the veins. All tumors expressed moderate U-II immunoreactivity in the cancer cells and vasculature. Here we demonstrate abundant expression of U-II in normal human kidneys and renal carcinoma. These findings suggest that the vasoactive and growth-mediator peptide U-II may contribute to the pathophysiology of the human renal system. 相似文献
70.
Activity of salivary glands in secreting honey‐elaborating enzymes in two subspecies of honeybee (Apis mellifera L)
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Aliaa A. Al‐Sherif Adel M. Mazeed Mohamed A. Ewis Emad A. Nafea El‐Seid E. Hagag Ahmed A. Kamel 《Physiological Entomology》2017,42(4):397-403
The activity of invertase, glucose oxidase and amylase in the cephalic (post‐cerebral) and thoracic salivary glands is determined in Egyptian and Carniolan honeybees (Apis mellifera L). For this purpose, three ages of worker bees are selected for enzyme assays. The results show that the three target enzymes are detected in the two glands during the three worker ages, except invertase, which cannot be detected in the cephalic gland of newly emerged bees of both subspecies. In both glands, the secretion of invertase is highest, followed by amylase and then glucose oxidase. In Carniolan bees, invertase secretion of the cephalic and thoracic glands increases gradually with age. In Egyptian bees, invertase increases with age only in the cephalic gland, whereas, in the thoracic gland, the highest secretion activity is detected in 10–15‐day‐old bees. The highest amounts of glucose oxidase and amylase in the cephalic gland are detected in newly emerged individuals of both Egyptian and Carniolan bees. In the thoracic gland, however, the highest activity of both enzymes is recorded only in newly emerged Egyptian bees. The results are discussed in the light of bee management and biological aspects of the two subspecies. 相似文献