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31.
32.
Kevin M. Smith Fahimeh Eivazi Kevin C. LangryJose A. P. Baptista de Almeida George W. Kenner 《Bioorganic chemistry》1979,8(4):485-495
An efficient total synthesis of 1,5-di(trideuteromethyl)protoporphyrin-IX (3) dimethyl ester from monopyrrole precursors is described, the synthesis proceeding through crystalline tripyrrene and a,c-biladiene salt intermediates. The 2- and 4-vinyl groups in (3) are formed from the corresponding (2-chloroethyl) substituents by way of base-promoted dehydrochlorination. In protio solvents, this synthetic step is shown to exchange out preferentially deuterons in the 1-methyl group, and this observation is exploited in an efficient synthesis of the 1,3-di(trideuteromethyl)protoporphyrin-IX (22) dimethyl ester from 2,4-diacetyldeuteroporphyrin-IX (20) dimethyl ester (which is in turn accessible from commercially available protoporphyrin-IX (5)). Thus, basic exchange in deuterated solvent of (20) gives the deuterated analog, which after reduction and dehydration gives the 1,3-di(trideuteromethyl)protoporphyrin-IX analog (22), in which the vinyl H2 and propionic CH2·CO functions have also become deuterated. 相似文献
33.
S O Andrade H O da Silva Lopes M de Almeida Barros G G Leite S M Dias M Saueressig D Nobre J A Temperini 《Arquivos do Instituto Biológico》1978,45(2):117-136
Aspects of photosensitization in bovines grazing on pastures of Brachiaria decumbens Stapf infested with Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures 45(2):117-136, 1978. This paper reports experimental studies on photosensitization in bovines grazing on different pastures of Brachiaria decumbens Stapf in the "Cerrados" region (Planaltina, DF). Climatic conditions, zinc content and occurence of fungi on pastures were investigated. Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures examined. Photosensitization was observed in one animal maintained on a pasture of B. decumbens formed with seeds from Australia. Clinical and necropsy data were similar to those related in literature for sporidesmin-intoxicated animals. An isolate of P. chartarum and samples of bovine bile were assayed for sporidesmin presence. 相似文献
34.
Many plants pollinated by nectar-foraging animals have to maintain a balance between legitimate visitor attraction strategies and mechanisms that minimize illegitimate visits. This study investigated how floral display and neighboring species composition influences nectar robbing by hummingbirds in the tropical ornithophilous herb Heliconia spathocircinata. We tested the role of inflorescence display, flower abundance, and neighboring species in the reduction of nectar robbing in H. spathocircinata. Our results indicate that nectar robbing hummingbird activity was higher in moderately large inflorescence displays and that the frequency of nectar robbing in H. spathocircinata decreases with increased flower abundance and the presence of neighboring plant species. Neighboring non-ornithophilous plants decreased the frequency of nectar robbing in H. spathocircinata flowers to a greater extent than ornithophilous ones. These results suggest that nectar robbing hummingbirds are attracted to similar conditions that attract legitimate visitors and that spatial aggregation and mixed-species displays may represent a mechanism to dilute nectar robbing effects at an individual level. 相似文献
35.
Amphiphilic detergent-soluble acetylcholinesterase (AChE) from Torpedo is converted to a hydrophilic form by digestion with phospholipase C from Trypanosoma brucei or from Bacillus cereus. This lipase digestion uncovers an immunological determinant which crossreacts with a complex carbohydrate structure present in the hydrophilic form of all variant surface glycoproteins (VSG) of T. brucei. This crossreacting determinant is also detected in human erythrocyte AChE after digestion with T. brucei lipase. From these results we conclude that the glycophospholipid anchors of protozoan VSG and of AChE of the two vertebrates share common structural features, suggesting that this novel type of membrane anchor has been conserved during evolution. 相似文献
36.
37.
Uncoupling effect of nitrite during denitrification by Pseudomonas fluorescens: An in vivo (31)P-NMR study 总被引:1,自引:0,他引:1
In vivo (31)P-NMR was used to investigate the basis for the inhibition of denitrification by nitrite accumulated endogenously by Pseudomonas fluorescens ATCC 17822 (biotype II) at pH 7.0. Cells were immobilized in kappa-carrageenan to obtain high cell concentrations in the NMR tube. Acetate and nitrate in two concentration ratios were supplied as electron donor and acceptor, respectively, to achieve different levels of nitrite accumulation. During denitrification, cells were able to maintain a pH gradient of approximately 0.4 to 0.5 units, but when nitrite accumulation reached values approximating 27 mM the transmembrane DeltapH collapsed sharply. Nitrite stimulated the reduction rate of nitrate; furthermore, at nitrite concentrations below 1 mM, activation of oxygen respiratory rates was observed in cells grown under aerobic conditions. The results provide evidence for nitrite acting as a protonophore (an uncoupler that increases the proton permeability of membranes by a shuttling mechanism). (c) 1996 John Wiley & Sons, Inc. 相似文献
38.
Characterization of Lipids and Proteins Associated to the Cell Wall of the Acapsular Mutant Cryptococcus neoformans Cap 67 下载免费PDF全文
Jhon H. S. Pires Felipe Gazos‐Lopes Milene C. Vallejo Tiago J. P. Sobreira Igor C. Almeida Rosana Puccia 《The Journal of eukaryotic microbiology》2015,62(5):591-604
Cryptococcus neoformans is an opportunistic human pathogen that causes life‐threatening meningitis. In this fungus, the cell wall is exceptionally not the outermost structure due to the presence of a surrounding polysaccharide capsule, which has been highly studied. Considering that there is little information about C. neoformans cell wall composition, we aimed at describing proteins and lipids extractable from this organelle, using as model the acapsular mutant C. neoformans cap 67. Purified cell wall preparations were extracted with either chloroform/methanol or hot sodium dodecyl sulfate. Total lipids fractionated in silica gel 60 were analyzed by electrospray ionization tandem mass spectrometry (ESI‐MS/MS), while trypsin digested proteins were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC‐MS/MS). We detected 25 phospholipid species among phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and phosphatidic acid. Two glycolipid species were identified as monohexosyl ceramides. We identified 192 noncovalently linked proteins belonging to different metabolic processes. Most proteins were classified as secretory, mainly via nonclassical mechanisms, suggesting a role for extracellular vesicles (EV) in transwall transportation. In concert with that, orthologs from 86% of these proteins have previously been reported both in fungal cell wall and/or in EV. The possible role of the presently described structures in fungal–host relationship is discussed. 相似文献
39.
Pedro Almeida Raquel Barbosa Polona Zalar Yumi Imanishi Kiminori Shimizu Benedetta Turchetti Jean‐Luc Legras Marta Serra Sylvie Dequin Arnaud Couloux Julie Guy Douda Bensasson Paula Gonçalves José Paulo Sampaio 《Molecular ecology》2015,24(21):5412-5427
The domestication of the wine yeast Saccharomyces cerevisiae is thought to be contemporary with the development and expansion of viticulture along the Mediterranean basin. Until now, the unavailability of wild lineages prevented the identification of the closest wild relatives of wine yeasts. Here, we enlarge the collection of natural lineages and employ whole‐genome data of oak‐associated wild isolates to study a balanced number of anthropic and natural S. cerevisiae strains. We identified industrial variants and new geographically delimited populations, including a novel Mediterranean oak population. This population is the closest relative of the wine lineage as shown by a weak population structure and further supported by genomewide population analyses. A coalescent model considering partial isolation with asymmetrical migration, mostly from the wild group into the Wine group, and population growth, was found to be best supported by the data. Importantly, divergence time estimates between the two populations agree with historical evidence for winemaking. We show that three horizontally transmitted regions, previously described to contain genes relevant to wine fermentation, are present in the Wine group but not in the Mediterranean oak group. This represents a major discontinuity between the two populations and is likely to denote a domestication fingerprint in wine yeasts. Taken together, these results indicate that Mediterranean oaks harbour the wild genetic stock of domesticated wine yeasts. 相似文献
40.
Horton R Gibson R Coggill P Miretti M Allcock RJ Almeida J Forbes S Gilbert JG Halls K Harrow JL Hart E Howe K Jackson DK Palmer S Roberts AN Sims S Stewart CA Traherne JA Trevanion S Wilming L Rogers J de Jong PJ Elliott JF Sawcer S Todd JA Trowsdale J Beck S 《Immunogenetics》2008,60(1):1-18
The human major histocompatibility complex (MHC) is contained within about 4 Mb on the short arm of chromosome 6 and is recognised
as the most variable region in the human genome. The primary aim of the MHC Haplotype Project was to provide a comprehensively
annotated reference sequence of a single, human leukocyte antigen-homozygous MHC haplotype and to use it as a basis against
which variations could be assessed from seven other similarly homozygous cell lines, representative of the most common MHC
haplotypes in the European population. Comparison of the haplotype sequences, including four haplotypes not previously analysed,
resulted in the identification of >44,000 variations, both substitutions and indels (insertions and deletions), which have
been submitted to the dbSNP database. The gene annotation uncovered haplotype-specific differences and confirmed the presence
of more than 300 loci, including over 160 protein-coding genes. Combined analysis of the variation and annotation datasets
revealed 122 gene loci with coding substitutions of which 97 were non-synonymous. The haplotype (A3-B7-DR15; PGF cell line)
designated as the new MHC reference sequence, has been incorporated into the human genome assembly (NCBI35 and subsequent
builds), and constitutes the largest single-haplotype sequence of the human genome to date. The extensive variation and annotation
data derived from the analysis of seven further haplotypes have been made publicly available and provide a framework and resource
for future association studies of all MHC-associated diseases and transplant medicine.
Horton and Gibson contributed equally to this work. 相似文献