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91.
Le Hellaye M Fortin N Guilloteau J Soum A Lecommandoux S Guillaume SM 《Biomacromolecules》2008,9(7):1924-1933
The amino poly(trimethylene carbonate)-NHt-Boc (PTMC-NHt-Boc) and poly(epsilon-caprolactone)-NH -Boc (PCL-NHt-Boc) were synthesized by ring-opening polymerization (ROP) of TMC or CL and subsequently deprotected into the corresponding PTMC-NH2 and PCL-NH2. These functional homopolymers were used as macroinitiators for the ROP of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG), consequently, giving the respective diblock copolymers PTMC-b-PBLG and PCL-b-PBLG in almost quantitative yields. The (co)polymers have been characterized by NMR and SEC analyses. DSC and IR studies confirmed the block structure of the copolymers and highlighted a phase separation between the rigid peptide (alpha-helix conformation) and the more flexible polyester segments. The self-assembly and the degradation behaviors of the copolymers depended on the nature of the polyester block and on the copolymer composition. Nanoparticles obtained from PBLG block copolymers were twice smaller ( RH < 100 nm) than those formed from PTMC and PCL homopolymers. Finally, their enzymatic degradation revealed that PTMC nanoparticles degraded faster than those made of PCL. 相似文献
92.
A Saccharomyces cerevisiae genome-wide mutant screen for altered sensitivity to K1 killer toxin 总被引:1,自引:0,他引:1
Pagé N Gérard-Vincent M Ménard P Beaulieu M Azuma M Dijkgraaf GJ Li H Marcoux J Nguyen T Dowse T Sdicu AM Bussey H 《Genetics》2003,163(3):875-894
Using the set of Saccharomyces cerevisiae mutants individually deleted for 5718 yeast genes, we screened for altered sensitivity to the antifungal protein, K1 killer toxin, that binds to a cell wall beta-glucan receptor and subsequently forms lethal pores in the plasma membrane. Mutations in 268 genes, including 42 in genes of unknown function, had a phenotype, often mild, with 186 showing resistance and 82 hypersensitivity compared to wild type. Only 15 of these genes were previously known to cause a toxin phenotype when mutated. Mutants for 144 genes were analyzed for alkali-soluble beta-glucan levels; 63 showed alterations. Further, mutants for 118 genes with altered toxin sensitivity were screened for SDS, hygromycin B, and calcofluor white sensitivity as indicators of cell surface defects; 88 showed some additional defect. There is a markedly nonrandom functional distribution of the mutants. Many genes affect specific areas of cellular activity, including cell wall glucan and mannoprotein synthesis, secretory pathway trafficking, lipid and sterol biosynthesis, and cell surface signal transduction, and offer new insights into these processes and their integration. 相似文献
93.
NMR structure of bacterial ribosomal protein l20: implications for ribosome assembly and translational control 总被引:1,自引:0,他引:1
Raibaud S Lebars I Guillier M Chiaruttini C Bontems F Rak A Garber M Allemand F Springer M Dardel F 《Journal of molecular biology》2002,323(1):143-151
L20 is a specific protein of the bacterial ribosome, which is involved in the early assembly steps of the 50S subunit and in the feedback control of the expression of its own gene. This dual function involves specific interactions with either the 23S rRNA or its messenger RNA. The solution structure of the free Aquifex aeolicus L20 has been solved. It is composed of an unstructured N-terminal domain comprising residues 1-58 and a C-terminal alpha-helical domain. This is in contrast with what is observed in the bacterial 50S subunit, where the N-terminal region folds as an elongated alpha-helical region. The solution structure of the C-terminal domain shows that several solvent-accessible, conserved residues are clustered on the surface of the molecule and are probably involved in RNA recognition. In vivo studies show that this domain is sufficient to repress the expression of the cistrons encoding L35 and L20 in the IF3 operon. The ability of L20 C-terminal domain to specifically recognise RNA suggests an assembly mechanism for L20 into the ribosome. The pre-folded C-terminal domain would make a primary interaction with a specific site on the 23S rRNA. The N-terminal domain would then fold within the ribosome, participating in its correct 3D assembly. 相似文献
94.
Phylogenetic relationships among 23 nonhuman primate (NHP) major histocompatibility complex class I chain-related gene (MIC) sequences, 54 confirmed human MICA alleles, and 16 human MICE alleles were constructed with methods of sequence analysis. Topology of the phylogenetic tree showed separation between NHP MICs and human MICs. For human MICs, the topology indicated monophyly for the MICB alleles, while MICA alleles were separated into two lineages, LI and LII. Of these, LI MICA alleles shared a common ancestry with gorilla (Ggo) MIC. One conservative amino acid difference and two nonconservative amino acid differences in the 3 domain were found between the MICA lineages. The nonconservative amino acid differences might imply structural and functional differences. Transmembrane (TM) trinucleotide-repeat variants were found to be specific to the MICA lineages such as A4, A9, and A10 to LI and A5 to LII. Variants such as A5.1 and A6 were commonly found in both MICA lineages. Based on these analyses, we postulate a polyphyletic origin for MICA alleles and their division into two lineages, LI and LII. As such, there would be 30 alleles in LI and 24 alleles in LII, thereby reducing the current level of polymorphism that exists, based on a presumed monophyletic origin. The lower degree of polymorphism in MICA would then be in line with the rest of the human major histocompatibility complex nonclassical class I genes. 相似文献
95.
Nicholas M. Fountain‐Jones Craig Packer Maude Jacquot F. Guillaume Blanchet Karen Terio Meggan E. Craft 《Ecology letters》2019,22(6):904-913
Pathogens are embedded in a complex network of microparasites that can collectively or individually alter disease dynamics and outcomes. Endemic pathogens that infect an individual in the first years of life, for example, can either facilitate or compete with subsequent pathogens thereby exacerbating or ameliorating morbidity and mortality. Pathogen associations are ubiquitous but poorly understood, particularly in wild populations. We report here on 10 years of serological and molecular data in African lions, leveraging comprehensive demographic and behavioural data to test if endemic pathogens shape subsequent infection by epidemic pathogens. We combine network and community ecology approaches to assess broad network structure and characterise associations between pathogens across spatial and temporal scales. We found significant non‐random structure in the lion‐pathogen co‐occurrence network and identified both positive and negative associations between endemic and epidemic pathogens. Our results provide novel insights on the complex associations underlying pathogen co‐occurrence networks. 相似文献
96.
Felipe Vaca-Paniagua Rosa María Alvarez-Gomez Hector Aquiles Maldonado-Martínez Carlos Pérez-Plasencia Veronica Fragoso-Ontiveros Federico Lasa-Gonsebatt Luis Alonso Herrera David Cantú Enrique Bargallo-Rocha Alejandro Mohar Geoffroy Durand Nathalie Forey Catherine Voegele Maxime Vallée Florence Le Calvez-Kelm James McKay Maude Ardin Stéphanie Villar Jiri Zavadil Magali Olivier 《PloS one》2015,10(5)
97.
Gilles Didier Laurent Debomy Maude Pupin Ming Zhang Alexander Grossmann Claudine Devauchelle Ivan Laprevotte 《BMC bioinformatics》2007,8(1):1
Background
In general, the construction of trees is based on sequence alignments. This procedure, however, leads to loss of informationwhen parts of sequence alignments (for instance ambiguous regions) are deleted before tree building. To overcome this difficulty, one of us previously introduced a new and rapid algorithm that calculates dissimilarity matrices between sequences without preliminary alignment. 相似文献98.
99.
Sehayek E Yu HJ von Bergmann K Lutjohann D Stoffel M Duncan EM Garcia-Naveda L Salit J Blundell ML Friedman JM Breslow JL 《Journal of lipid research》2004,45(9):1608-1613
Screening of 932 adults on the Pacific island of Kosrae for plasma plant sterol levels disclosed three subjects, two of them asymptomatic, with phytosterolemia. Sequencing the ATP binding cassette subfamily G member 8 (ABCG8) gene revealed a novel exon 2 mutation that causes a change in codon 24 from glutamine to histidine and a frame shift followed by a premature stop codon, precluding the formation of a functional ABCG8 protein. Genotyping of 1,090 Kosraens revealed 150 as carriers, a 13.8% carrier rate. DNA sequencing of 67 carriers revealed the same mutation as in the probands. In carriers, plasma campesterol and sitosterol levels were 55% and 30% higher, respectively, than in noncarriers. Moreover, compared with noncarriers, carriers showed 21% lower plasma levels of lathosterol, a surrogate marker for cholesterol biosynthesis. There was no difference between the groups in plasma total cholesterol, triglycerides, apolipoprotein B, or apolipoprotein A-I levels. In summary, on the island of Kosrae, a strong founder effect of a mutant ABCG8 allele results in a large number of carriers with increased plasma plant sterol levels and decreased lathosterol levels. The latter finding suggests that heterozygosity for a mutated ABCG8 allele results in a modest increase in dietary cholesterol absorption and a decrease in cholesterol biosynthesis. 相似文献
100.
Water provision alters wildebeest adaptive habitat selection and resilience in the Central Kalahari
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Moses Selebatso Emily Bennitt Glyn Maude Richard W. S. Fynn 《African Journal of Ecology》2018,56(2):225-234
Wildlife populations in semi‐arid regions require unrestricted mobility along ecological gradients and across large landscapes to enable adaptive responses to seasonal variability and patchy resources. In the Kalahari region of Botswana, herbivore populations historically depended on seasonal access to the nutrient‐rich Schwelle area in the wet season and to water from the Boteti River during drought periods. Blue wildebeest Connochaetes taurinus in the Central Kalahari Game Reserve (CKGR) have lost access to these key habitats due to fences and encroachment of livestock and humans. We deployed satellite collars onto 10 female wildebeest in the CKGR to examine seasonal movements and habitat selection in relation to the environmental conditions and fragmented ecosystem. Wildebeest favoured open, short‐grass pan habitats in all seasons, probably in response to better forage quality and lower predation risk. The ability to remain in pan habitats during the dry season was a result of artificial water provision. A wildebeest herd that had no artificial water in its home range survived the dry season, whereas those wildebeest that were accustomed to water provision died when their water points failed in the dry season. Thus, water provision altered adaptive behaviour and reduced resilience of the population to the arid environment. 相似文献