华西银腊梅挥发油化学成分的研究

用水蒸气蒸馏法提取华西银腊梅挥发油,并用气相色谱-质谱(GC-MS)联用技术对其挥发油的化学成分进行分析,结果共鉴定了其中的39种成分,所鉴定成分含量约占总检出量的87.83%。其化学成分主要为(Z,Z)-9,12-十八碳二烯酸甲酯(9.00%),壬醛(5.83%),二十一烷(5.69%),二十烷(5.08%),辛炔酸(4.50%),2,6,10,15-四甲基十七烷(3.93%),(Z)-6-十八烯酸甲酯(3.65%),3,8-二甲基十一烷(3.52%),1-十六碳炔(3.31%),肉豆蔻酸(2.86%),月桂醛(2.81%),壬酸(2.23%),5,6,7,7α-四氢-4,4,7α三甲基-2(4H)-苯并呋喃酮(2.18%)等。     

The cell death protease Kex1p is essential for hypochlorite-induced apoptosis in yeast

Following microbial pathogen invasion, the human immune system of activated phagocytes generates and releases the potent oxidant hypochlorous acid (HOCl), which contributes to the killing of menacing microorganisms. Though tightly controlled, HOCl generation by the myeloperoxidase-hydrogen peroxide-chloride system of neutrophils/monocytes may occur in excess and lead to tissue damage. It is thus of marked importance to delineate the molecular pathways underlying HOCl cytotoxicity in both microbial and human cells. Here, we show that HOCl induces the generation of reactive oxygen species (ROS), apoptotic cell death and the formation of specific HOCl-modified epitopes in the budding yeast Saccharomyces cerevisiae. Interestingly, HOCl cytotoxicity can be prevented by treatment with ROS scavengers, suggesting oxidative stress to mediate the lethal effect. The executing pathway involves the pro-apoptotic protease Kex1p, since its absence diminishes HOCl-induced production of ROS, apoptosis and protein modification. By characterizing HOCl-induced cell death in yeast and identifying a corresponding central executor, these results pave the way for the use of Saccharomyces cerevisiae in HOCl research, not least given that it combines both being a microorganism as well as a model for programmed cell death in higher eukaryotes.     

The Chlorite Dismutase (HemQ) from Staphylococcus aureus Has a Redox-sensitive Heme and Is Associated with the Small Colony Variant Phenotype

The chlorite dismutases (C-family proteins) are a widespread family of heme-binding proteins for which chemical and biological roles remain unclear. An association of the gene with heme biosynthesis in Gram-positive bacteria was previously demonstrated by experiments involving introduction of genes from two Gram-positive species into heme biosynthesis mutant strains of Escherichia coli, leading to the gene being renamed hemQ. To assess the gene product''s biological role more directly, a Staphylococcus aureus strain with an inactivated hemQ gene was generated and shown to be a slow growing small colony variant under aerobic but not anaerobic conditions. The small colony variant phenotype is rescued by the addition of exogenous heme despite an otherwise wild type heme biosynthetic pathway. The ΔhemQ mutant accumulates coproporphyrin specifically under aerobic conditions. Although its sequence is highly similar to functional chlorite dismutases, the HemQ protein has no steady state reactivity with chlorite, very modest reactivity with H₂O₂ or peracetic acid, and no observable transient intermediates. HemQ''s equilibrium affinity for heme is in the low micromolar range. Holo-HemQ reconstituted with heme exhibits heme lysis after <50 turnovers with peroxide and <10 turnovers with chlorite. The heme-free apoprotein aggregates or unfolds over time. IsdG-like proteins and antibiotic biosynthesis monooxygenases are close sequence and structural relatives of HemQ that use heme or porphyrin-like organic molecules as substrates. The genetic and biochemical data suggest a similar substrate role for heme or porphyrin, with possible sensor-regulator functions for the protein. HemQ heme could serve as the means by which S. aureus reversibly adopts an SCV phenotype in response to redox stress.     

Two nucleoside uptake systems in Lactococcus lactis: competition between purine nucleosides and cytidine allows for modulation of intracellular nucleotide pools

A method for measuring internal nucleoside triphosphate pools of lactococci was optimized and validated. This method is based on extraction of (33)P-labeled nucleotides with formic acid and evaluation by two-dimensional chromatography with a phosphate buffer system for the first dimension and with an H(3)BO(3)-LiOH buffer for separation in the second dimension. We report here the sizes of the ribo- and deoxyribonucleotide pools in laboratory strain MG1363 during growth in a defined medium. We found that purine- and pyrimidine-requiring strains may be used to establish physiological conditions in batch fermentations with altered nucleotide pools and growth rates by addition of nucleosides in different combinations. Addition of cytidine together with inosine to a purine-requiring strain leads to a reduction in the internal purine nucleotide pools and a decreased growth rate. This effect was not seen if cytidine was replaced by uridine. A similar effect was observed if cytidine and inosine were added to a pyrimidine-requiring strain; the UTP pool size was significantly decreased, and the growth rate was reduced. To explain the observed inhibition, the nucleoside transport systems in Lactococcus lactis were investigated by measuring the uptake of radioactively labeled nucleosides. The K(m) for for inosine, cytidine, and uridine was determined to be in the micromolar range. Furthermore, it was found that cytidine and inosine are competitive inhibitors of each other, whereas no competition was found between uridine and either cytidine or inosine. These findings suggest that there are two different high-affinity nucleoside transporters, one system responsible for uridine uptake and another system responsible for the uptake of all purine nucleosides and cytidine.     

Asymmetrical,water-soluble phthalocyanine dyes for covalent labeling of oligonucleotides

Two new water-soluble, porphyrazine (Pz) dyes containing an isothiocyanate function for covalent linking have each been prepared by cross condensation of two different aromatic dinitriles, one containing carboxylates for solubilizing purposes and the other containing a nitro group for conversion into the labeling function. The initial mononitrotricarboxylato Pzs have been purified to homogeneity from the mixture of Pz congeners formed in the condensation reaction by anion exchange chromatography. The phthalocyanine dye 1 has an absorption maxima at 683 nm while the trinaphthoporphyrazine dye 2 has an absorption maxima at 755 nm, due to the increased size of the aromatic system. Both dyes were successfully conjugated to oligonucleotide primers, showing their potential for use in near-infrared-based DNA diagnostic applications.     

Range-wide fragmentation in a threatened fish associated with post-European settlement modification in the Murray–Darling Basin,Australia

Distinguishing the relative influence of historic (i.e. natural) versus anthropogenic factors in metapopulation structure is an important but often overlooked step in management programs of threatened species. Biotas in freshwater wetlands and floodplains, such as those in the Murray–Darling Basin (MDB)—one of Australia’s most impacted ecosystems, are particularly susceptible to anthropogenic fragmentation. Here we present a comprehensive multilocus assessment of genetic variation in the threatened southern pygmy perch Nannoperca australis (578 individuals; 45 localities; microsatellite, allozyme and mitochondrial DNA datasets), an ecological specialist with low dispersal potential. We assess patterns of spatial structure and genetic diversity in populations spanning the highly fragmented MDB and test whether recent anthropogenic modification has disrupted range-wide connectivity. We detected strong and hierarchical population structure, very low genetic diversity and lack of contemporary gene flow across the MDB. In contrast, the apparent absence of pronounced or long-term phylogeographic structure suggests that observed population divergences generally do not reflect deeply historic natural fragmentation. Coalescent-based analyses supported this inference, revealing that divergence times between populations from the upper and lower MDB fall into the period of European settlement. It appears that the observed contemporary isolation of populations is partly explained by the severe modification of the MDB post-dating the onset of European settlement. Our integrated approach substantially improves the interpretation of how fragmentation impacts present-day biodiversity. It also provides novel contributions for risk-assessing management actions in the context of captive breeding and translocations of small freshwater fishes, a group of increasing global conservation concern.