Parallel synthesis of peptide libraries using microwave irradiation

The application of microwave irradiation to solid-phase peptide synthesis increases product purity and reduces reaction time. Parallel synthesis in 96-well polypropylene filter plates with microwave irradiation is an efficient method for the rapid generation of combinatorial peptide libraries in sufficient purity to assay the products directly for biological activity without HPLC purification. In this protocol, the solid-phase support is arrayed into each well of a 96-well plate, reagents are delivered using a multichannel pipette and a microwave reactor is used to complete peptide coupling reactions in 6 min and Fmoc-removal reactions in 4 min under temperature-controlled conditions. The microwave-assisted parallel peptide synthesis protocol has been used to generate a library of difficult hexa-beta-peptides in 61% average initial purity (50% yield) and has been applied to the preparation of longer alpha- and beta-peptides. Using this protocol, a library of 96 different hexapeptides can be synthesized in 24 h (excluding characterization).     

Roles of salt and conformation in the biological and physicochemical behavior of protegrin-1 and designed analogues: correlation of antimicrobial, hemolytic, and lipid bilayer-perturbing activities

Protegrins are short (16-18 residues) cationic peptides from porcine leukocytes that display potent, broad-spectrum antimicrobial activity. Protegrin-1 (PG-1), one of five natural homologues, adopts a rigid beta-hairpin structure that is stabilized by two disulfide bonds. We have previously employed the principles of beta-hairpin design to develop PG-1 variants that lack disulfide bonds but nevertheless display potent antimicrobial activity [Lai, J. R., Huck, B. R., Weisblum, B., and Gellman, S. H. (2002) Biochemistry 41, 12835-12842.]. The activity of these disulfide-free variants, however, is attenuated in the presence of salt, and the activity of PG-1 itself is not. Salt-induced inactivation of host-defense peptides, such as human defensins, is thought to be important in some pathological situations (e.g., cystic fibrosis), and the variation in salt-sensitivity among our PG-1 analogues offers a model system with which to explore the origins of these salt effects. We find that the variations in antimicrobial activity among our peptides are correlated with the folding propensities of these molecules and with the extent to which the peptides induce leakage of contents from synthetic liposomes. Comparable correlations were observed between folding and hemolytic activity. The extent to which added salt reduces antimicrobial activity parallels salt effects on vesicle perturbation, which suggests that the biological effects of high salt concentrations arise from modulation of peptide-membrane interactions.     

Genetic analysis of resistance to Puccinia striiformis f.sp. tritici in cv. Aflak at adult plant stage

In order to investigate heritability and gene action for yellow rust resistance in wheat, a resistance yellow rust cultivar Aflak was crossed to susceptible cultivar Avocet‘s’. Parents, F₁, F₂ and F₃ generations were cultured according to randomised complete block design with two replications in the research station of Gharakhil, Iran. Parents and other generations were inoculated with 70E0A+ race. Traits including severity and infection type were recorded and then coefficient of infection was calculated. For this trait, generations mean and variance analysis were performed and results showed that there were significant differences among generations for coefficient of infection. Results showed that in addition to additive and dominance effects, at least one kind of epistasis interaction (additive × additive) control this trait. Although additive and dominance effects control this trait, but with attention to generations variance analysis, the results showed that additive variance had important role to control this trait.