Synthesis and alkylation of aza‐glycinyl dipeptide building blocks

Aza‐glycinyl dipeptides are useful building blocks for the synthesis of a diverse array of azapeptides. The construction of the aza‐glycine residue is however challenging, because of the potential for side reactions, such as those leading to formation of oxadiazalone, hydantoin and symmetric urea by‐products. Employing N,N′‐disuccinimidyl carbonate to activate benzophenone hydrazone, we have developed a more efficient approach for the synthesis of aza‐glycinyl dipeptides. Alkylation of the semicarbazone of the resulting protected aza‐glycinyl dipeptides using tetraethylammonium hydroxide and propargyl bromide provided an efficient entry into the aza‐propargylglycinyl peptide building blocks, which have served previously in various reactions including Sonogashira cross‐couplings, dipolar cycloadditions and intramolecular exo‐dig cycloadditions to furnish a variety of azapeptide building blocks. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

The importance of being kinked: role of Pro residues in the selectivity of the helical antimicrobial peptide P5

Antimicrobial peptides (AMPs) are promising compounds for developing new antibiotic drugs against drug‐resistant bacteria. Many of them kill bacteria by perturbing their membranes but exhibit no significant toxicity towards eukaryotic cells. The identification of the features responsible for this selectivity is essential for their pharmacological development. AMPs exhibit few conserved features, but a statistical analysis of an AMP sequence database indicated that many α‐helical AMPs surprisingly have a helix‐breaking Pro residue in the middle of their sequence. To discriminate among the different possible hypotheses for the functional role of this feature, we designed an analogue of the antimicrobial peptide P5, in which the central Pro was deleted (analogue P5Del). Pro removal resulted in a dramatic increase of toxicity. This was explained by the observation that P5Del binds both charged and neutral membranes, whereas P5 has no appreciable affinity towards neutral bilayers. CD and simulative data provided a rationalization of this behavior. In solution P5, due to the presence of Pro, attains compact conformations, in which its apolar residues are partially shielded from the solvent, whereas P5Del is more helical. These structural differences reduce the hydrophobic driving force for association of P5 to neutral membranes, whereas its binding to anionic bilayers can still take place because of electrostatic attraction. After membrane binding, the Pro residue does not preclude the attainment of a membrane‐active amphiphilic helical conformation. These findings shed light on the role of Pro residues in the selectivity of AMPs and provide hints for the design of new, highly selective compounds. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Introduction of histidine units using benzotriazolide activation

N^α‐Boc‐N^im‐(4‐toluenesulfonyl‐l ‐histidylbenzotriazole) enables convenient acylation of N‐, O‐, S‐, and C‐nucleophiles with no detectable racemization. We report efficient syntheses of novel histidine‐containing di‐, tri‐, and tetra‐peptides and models for the preparation of potentially biologically active histidine N‐, O‐, S‐, and C‐conjugates. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Novel cytotoxic exhibition mode of antimicrobial peptide anoplin in MEL cells,the cell line of murine Friend leukemia virus‐induced leukemic cells

Anoplin is a recently discovered antimicrobial peptide (AMP) isolated from the venom sac of the spider wasp Anoplius samariensis, and it is one of the shortest α‐helical AMP found naturally to date consisting of only ten amino acids. Previous results showed that anoplin exhibits potent antimicrobial activity but little hemolytic activity. In this study, we synthesized anoplin, studied its cytotoxicity in Friend virus‐induced leukemia cells [murine erythroleukemia (MEL) cells], and proposed its possible mechanism. Our results showed that anoplin could inhibit the proliferation of MEL cells in a dose‐dependent and time‐dependent manner via disrupting the integrity of cell membrane, which indicated that anoplin exerts its cytotoxicity efficacy. In addition, the cell cycle distribution of MEL cells was arrested in the G₀/G₁ phase significantly. However, anoplin could not induce obvious apoptosis in MEL cells, as well as anoplin could not induce visible changes on morphology and quantity in the bone marrow cells isolated from normal mice. All of these results indicate that anoplin, as generally believed, is a selective AMP, a value characteristic in the design of safe therapeutic agents. The cytotoxicity of anoplin on MEL cells was mainly attributable to the plasma membrane perturbation and also to the intracellular events such as the arrest of cell cycle. Although this is an initial study that explored the activity of anoplin in vitro rather than in vivo, with the increasing resistance of conventional chemotherapy, there is no doubt that anoplin has desirable feature to be developed as a novel and selective anticancer agent. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Turbellarian assemblages in freshwater lagoons in southern Brazil

Turbellarians, which typically feed on bacteria, algae, rotifers, oligochaetes, dipteran larvae, microcrustaceans, and other organisms, are abundant in diverse types of wetlands. Despite their importance, abundance, and species richness in freshwater environments, turbellarians are seldom considered in studies on biodiversity. We analyzed the structure of turbellarian communities in shore areas of three categories of permanent wetlands classified according to their perimeter as small, intermediate, and large during an annual cycle. In total, 1847 turbellarians were collected representing 42 species and 15 genera, from the orders Catenulida, Macrostomida, Lecithoepitheliata, Rhabdocoela, and Tricladida. Sixteen species were common to the three categories of wetlands, whereas nineteen species were unique to a particular category. Species composition varied among wetlands of different sizes; small, intermediate, and large wetlands had different dominant species. We found seasonal differences in community composition over the year, but no significant differences in mean values of observed species richness among wetlands with different sizes and among seasonal samples. The estimated species richness was, however, higher in the small wetlands, followed by the large and intermediate wetlands. In the summer, abundance was significantly lower in the small water bodies than in the intermediate and large bodies of water. Our results reinforce the need for conservation of wetlands of different sizes.     

A conceptual model of the Amblyomma americanum life cycle in northeast Missouri

The geographic distribution of Amblyomma americanum (the lone star tick) has increased as has its role as a pathogen vector. The objectives of this study were to determine seasonal activity patterns of each life stage of A. americanum in the northwestern part of the species range and the relationship of these activity patterns among life stages and degree days. Tick activity was monitored over four years since 2007 in a forest and old field habitat located in northeast Missouri. Every other week from February to December, ticks were collected using bait and drag methods. Autocorrelations demonstrated yearly seasonal patterns in each life stage and cross‐correlations between life stages depicted a relationship between activity at a life stage and the previous stage's activity. Cross‐correlations indicated that degree days were related to activity. These data indicated that A. americanum generally complete their life cycle in a minimum of two years in northeast Missouri, with overwintering occurring predominantly in the nymphal and adult stages. These data provide a baseline to compare the life cycle of A. americanum in northeast Missouri to populations in different parts of the species range or at different times in the region.     

Comparison of insecticidal paint and deltamethrin against Triatoma infestans (Hemiptera: Reduviidae) feeding and mortality in simulated natural conditions

The vector of Chagas disease, Triatoma infestans, is largely controlled by the household application of pyrethroid insecticides. Because effective, large‐scale insecticide application is costly and necessitates numerous trained personnel, alternative control techniques are badly needed. We compared the residual effect of organophosphate‐based insecticidal paint (Inesfly 5A IGR? (I5A)) to standard deltamethrin, and a negative control, against T. infestans in a simulated natural environment. We evaluated mortality, knockdown, and ability to take a blood meal among 5^th instar nymphs. I5A paint caused significantly greater mortality at time points up to nine months compared to deltamethrin (Fisher's Exact Test, p < 0.01 in all instances). A year following application, mortality among nymphs in the I5A was similar to those in the deltamethrin (χ2 = 0.76, df=1, p < 0.76). At months 0 and 1 after application, fewer nymphs exposed to deltamethrin took a blood meal compared to insects exposed to paint (Fisher's Exact Tests, p < 0.01 and p < 0.01, respectively). Insecticidal paint may provide an easily‐applied means of protection against vectors of Chagas disease.