Synthesis of peptides employing 9-fluorenylmethyl chloroformate as a coupling agent

Summary The synthesis of peptides employing 9-fluorenylmethyl chloroformate (Fmoc-Cl) as a coupling agent has been described. The method is simple, efficient and rapid. All the peptides have been obtained in good yield (70–95%). Furthermore, both the¹H NMR and the HPLC studies on Fmoc-Phg-Phe-OMe and Fmoc-D-Phg-Phe-OMe revealed that the coupling is free from racemization.     

Density‐dependence in common tree species in a tropical dry forest in Mudumalai,southern India

Abstract. Density‐dependence in tree population dynamics has seldom been examined in dry tropical forests. Using long‐term data from a large permanent plot, this study examined 16 common species in a dry tropical forest in southern India for density‐dependence. Employing quadrat‐based analyses, correlations of mortality, recruitment and population change with tree densities were examined. Mortality in 1–10 cm diameter trees was largely negatively correlated with conspecific density, whereas mortality in > 10 cm diameter trees was positively correlated. Mortality was, however, largely unaffected by the basal area and abundance of heterospecific trees. Recruitment was poor in most species, but in Lagerstroemia microcarpa (Lythraceae), Tectona grandis (Verbenaceae) and Cassia fistula (Fabaceae), species that recruited well, strong negative correlations of recruitment with conspecific basal area and abundance were found. In a few other species that could be tested, recruitment was again negatively correlated with conspecific density. In Lagerstroemia, recruitment was positively correlated with the basal area and abundance of heterospecific trees, but these correlations were non‐significant in other species. Similarly, although the rates of population change were negatively correlated with conspecific density they were positive when dry‐season ground fires occurred in the plot. Thus, the observed positive density‐dependence in large‐tree mortality and the negative density‐dependence in recruitment in many species were such that could potentially regulate tree populations. However, repeated fires influenced density‐dependence in the rates of population change in a way that could promote a few common species in the tree community.     

Transposon-Like Organization of the Plasmid-Borne Organophosphate Degradation (opd) Gene Cluster Found in Flavobacterium sp.

Several bacterial strains that can use organophosphate pesticides as a source of carbon have been isolated from soil samples collected from diverse geographical regions. All these organisms synthesize an enzyme called parathion hydrolase, and in each case the enzyme is encoded by a gene (opd) located on a large indigenous plasmid. These plasmids show considerable genetic diversity, but the region containing the opd gene is highly conserved. Two opd plasmids, pPDL2 from Flavobacterium sp. and pCMS1 from Pseudomonas diminuta, are well characterized, and in each of them a region of about 5.1 kb containing the opd gene shows an identical restriction pattern. We now report the complete sequence of the conserved region of plasmid pPDL2. The opd gene is flanked upstream by an insertion sequence, ISFlsp1, that is a member of the IS21 family, and downstream by a Tn3-like element encoding a transposase and a resolvase. Adjacent to opd but transcribed in the opposite direction is an open reading frame (orf243) with the potential to encode an aromatic hydrolase somewhat similar to Pseudomonas putida TodF. We have shown that orf243 encodes a polypeptide of 27 kDa, which plays a role in the degradation of p-nitrophenol and is likely to act in concert with opd in the degradation of parathion. The linkage of opd and orf243, the organization of the genes flanking opd, and the wide geographical distribution of these genes suggest that this DNA sequence may constitute a complex catabolic transposon.     

Impact of the introduced yellow crazy ant Anoplolepis gracilipes on Bird Island, Seychelles

The introduced yellow crazy ant or long-legged ant Anoplolepis gracilipes was first reported in Seychelles in 1969 and now occurs on at least nine islands in the Central Seychelles. We describe the yellow crazy ant's effects on vegetation and invertebrate communities on one of these, Bird Island; in 2000, Anoplolepis (first reported in 1991) occurred there at densities at least 80 times higher than on other islands in the Central Seychelles. They were associated with high densities of coccid scale insects on foliage, especially of the native tree Pisonia grandis, in some instances causing tree death. Yellow crazy ants on Bird Island also significantly affected invertebrate communities on foliage and on the ground, both in terms of taxonomic composition and the density of specific taxa, apparently causing the local exclusion of some invertebrates.     

The Mechanism of Action of Multidrug-Resistance-Linked P-Glycoprotein

P-glycoprotein (Pgp), the ATP-binding cassette (ABC) transporter, confers multidrug resistance to cancer cells by extruding cytotoxic natural product amphipathic drugs using the energy of ATP hydrolysis. Our studies are directed toward understanding the mechanism of action of Pgp and recent work deals with the assessment of interaction between substrate and ATP sites and elucidation of the catalytic cycle of ATP hydrolysis. The kinetic analyses of ATP hydrolysis by reconstituted purified Pgp suggest that ADP release is the rate-limiting step in the catalytic cycle and the substrates exert their effect by modulating ADP release. In addition, we provide evidence for two distinct roles for ATP hydrolysis in a single turnover of Pgp, one in the transport of drug and the other in effecting conformational changes so as to reset the transporter for the next catalytic cycle. Detailed kinetic measurements determined that both nucleotide-binding domains behave symmetrically and during individual hydrolysis events the ATP sites are recruited in a random manner. Furthermore, only one nucleotide site hydrolyzes ATP at any given time, causing (in this site) a conformational change that drastically decreases (>30-fold) the affinity of the second site for ATP-binding. Thus, the blocking of ATP-binding to the second site while the first one is in catalytic conformation appears to be the basis for the alternate catalytic cycle of ATP hydrolysis by Pgp, and this may be applicable as well to other ABC transporters linked with the development of multidrug resistance.     

A nuclear SH3 domain-binding protein that colocalizes with mRNA splicing factors and intermediate filament-containing perinuclear networks

A protein (SNP70) has been isolated that binds to the Src homology domain 3 of p47(phox), p85alpha, and c-src. Cloning and sequencing of the polypeptide revealed it to be a 70-kDa protein that has a number of potential domains, including Src homology 3 binding motifs and several nuclear localization signals. Immunofluorescence using anti-peptide antibodies revealed SNP70 to be primarily concentrated in the nucleus but excluded from nucleoli, in interphase cells. However, it was distributed throughout the cytoplasm in dividing cells. Extraction and subfractionation experiments indicated that SNP70 did not bind directly to DNA but did bind to poly(G)-rich oligonucleotides and was resistant to extraction with non-ionic detergents but was solubilized by treatment with RNase, high salt, or ammonium sulfate. Double-immunofluorescence experiments showed that SNP70 co-localized with two pre-mRNA splicing factors SC35 and U2B" within the nucleus. A population of SNP70 was found outside the nucleus, and double-immunofluorescence and immunoelectron microscopy demonstrated that it associated with vimentin-containing intermediate filaments, particularly those surrounding the nucleus. The data suggest that SNP70 associates with nuclear or perinuclear filaments and may play a role in the regulation of pre-mRNA processing.     

Prevalence of HIV,Hepatitis B and C Infections and an Assessment of HCV-Genotypes and Two IL28B SNPs among People Who Inject Drugs in Three Regions of Nepal

As part of a comprehensive health care programme for people who use drugs in Nepal, HIV and viral hepatitis B and C status—including risk factors, HCV-genotypes and co-infections—as well as two IL28B Single-nucleotide polymorphisms (SNPs) were assessed for a random sample of 401 people who inject drugs in three regions of Nepal: mid-western Terrai (Nepalgunj), the eastern region (Dharan, Biratnagar) and the central region (Kathmandu, Lalitpur and Chitwan). Individuals were included who showed at least a minimum of health care seeking behaviour. This latter criterion was defined by being registered with any organisation offering health services. The average age of the participants was 30.5 yrs, and the average length of intravenous drug use was 8.5 yrs. The prevalence rates of HBsAg, anti-HIV antibodies and HCV-RNA were 3.5%, 13.8% and 41.9%, respectively. Spontaneous HCV clearance was evident in 16% of all of those who tested positive for anti-HCV antibodies. Independent risk factors for HCV-RNA positivity were age, gender, geographical region, duration of injecting drug use, history of imprisonment and HIV co-infection. In the age group ≤24 yrs, the rate of spontaneous HCV clearance was 43.5%. Overall, 59.8% of HCV infections were caused by HCV genotype 3 and 40.2% by HCV genotype 1. No other HCV genotypes were identified in this study. The IL28B SNP rs12979860 and rs8099917 were identified in 122 patients, and 75.4% of all participants had both favourable genotypes rs12979860 C/C and rs8099917 T/T.     

Bioaerosols from municipal and animal wastes: background and contemporary issues

Global population increases, coupled with intensive animal and livestock production practices, have resulted in the generation, accumulation, and disposal of large amounts of wastes around the world. Aerosolization of microbial pathogens, endotoxins, odors, and dust particles is an inevitable consequence of the generation and handling of waste material. Bioaerosols can be a source of microbial pathogens, endotoxins, and other allergens. Given the close proximity of population centers to concentrated animal-rearing operations and municipal treatment facilities in many parts of the world, there is concern regarding the occupational and public health impacts associated with the exposure to bioaerosols from municipal and animal wastes. Major advances have been made in our understanding of bioaerosol characteristics, identifying the hazards, and identifying possible human and animal health links with aerosolized pathogens and allergens. However, significant knowledge and technology gaps still exist. These include a lack of clear understanding of the fate and transport of bioaerosols, especially within the open environment, an inability to accurately predict the health risks associated with bioaerosolized pathogens, and a lack of standardized bioaerosol sampling protocols, and efficient samplers. This review synthesizes the information related to bioaerosols and addresses the contemporary issues associated with bioaerosols from municipal and animal wastes, with a focus on pathogens.