Have you tried turning it off and on again? Oscillating selection to enhance fitness-landscape traversal in adaptive laboratory evolution experiments.

Adaptive Laboratory Evolution (ALE) is a powerful tool for engineering and understanding microbial physiology. ALE relies on the selection and enrichment of mutations that enable survival or faster growth under a selective condition imposed by the experimental setup. Phenotypic fitness landscapes are often underpinned by complex genotypes involving multiple genes, with combinatorial positive and negative effects on fitness. Such genotype relationships result in mutational fitness landscapes with multiple local fitness maxima and valleys. Traversing local maxima to find a global maximum often requires an individual or sub-population of cells to traverse fitness valleys. Traversing involves gaining mutations that are not adaptive for a given local maximum but are necessary to 'peak shift' to another local maximum, or eventually a global maximum. Despite these relatively well understood evolutionary principles, and the combinatorial genotypes that underlie most metabolic phenotypes, the majority of applied ALE experiments are conducted using constant selection pressures. The use of constant pressure can result in populations becoming trapped within local maxima, and often precludes the attainment of optimum phenotypes associated with global maxima. Here, we argue that oscillating selection pressures is an easily accessible mechanism for traversing fitness landscapes in ALE experiments, and provide theoretical and practical frameworks for implementation.

Direct, Late-Stage Mono-N-arylation of Pentamidine: Method Development, Mechanistic Insight, and Expedient Access to Novel Antiparastitics against Diamidine-Resistant Parasites.

A selective mono-N-arylation strategy of amidines under Chan-Lam conditions is described. During the reaction optimization phase, the isolation of a mononuclear Cu(II) complex provided unique mechanistic insight into the operation of Chan-Lam mono-N-arylation. The scope of the process is demonstrated, and then applied to access the first mono-N-arylated analogues of pentamidine. Sub-micromolar activity against kinetoplastid parasites was observed for several analogues with no cross-resistance in pentamidine and diminazene-resistant trypanosome strains and against Leishmania mexicana. A fluorescent mono-N-arylated pentamidine analogue revealed rapid cellular uptake, accumulating in parasite nuclei and the kinetoplasts. The DNA binding capability of the mono-N-arylated pentamidine series was confirmed by UV-melt measurements using AT-rich DNA. This work highlights the potential to use Chan-Lam mono-N-arylation to develop therapeutic leads against diamidine-resistant trypanosomiasis and leishmaniasis.

Mono-Substituted Hydrocarbon Diastereomer Combinations Reveal Stapled Peptides with High Structural Fidelity.

Modified peptides, such as stapled peptides, which replicate the structure of α-helical protein segments, represent a potential therapeutic advance. However, the 3D solution structure of these stapled peptides is rarely explored beyond the acquisition of circular dichroism (CD) data to quantify bulk peptide helicity; the detailed backbone structure, which underlies this, is typically undefined. Diastereomeric stapled peptides based on helical sections of three proteins (αSyn, Cks1 and CK1α) were generated; their overall helicity was quantified by CD; and the most helical peptide from each series was selected for structural analysis. Solution-phase models for the optimised peptides were generated using NMR-derived restraints and a modified CHARMM22 force field. Comparing these models with PDB structures allowed deviation between the stapled peptides and critical helical regions to be evaluated. These studies demonstrate that CD alone is not sufficient to assess the structural fidelity of a stapled peptide.

Psychosocial risk and protective factors associated with perpetration of gender-based violence in a community sample of men in rural KwaZulu-Natal, South Africa.

BACKGROUND: Rates of gender-based violence (GBV) in South Africa (SA) are among the highest in the world. In societies where social ideals of masculinity encourage male dominance and control over women, gender power imbalances contribute to male perpetration and women's vulnerability. The drivers that cause men to perpetrate GBV and those that lead to HIV overlap and interact in multiple and complex ways. Multiple risk and protective factors for GBV perpetration by males operate interdependently at a number of levels; at the individual level, these include chronic anxiety and depression, which have been shown to lead to risky sexual behaviours. OBJECTIVES: (i) To examine psychosocial risk factors (symptoms of anxiety and depression) as well as protective factors (social support and self-esteem) as self-reported by a cohort of males in rural KwaZulu-Natal (KZN) Province, SA; and (ii) to determine whether there are differences in anxiety, depression, social support and self-esteem between perpetrators and non-perpetrators. METHODS: A cross-sectional study using quasi-probability cluster sampling of 13 of 28 wards in Harry Gwala District, KZN. Participants were then randomly chosen from each ward proportionate to size. RESULTS: The participants were relatively young (median age 22 years); over half were schoolgoers, and 91.3% had never married. Over 43% of the sample reported clinical levels of anxiety and depressive symptoms on the Brief Symptom Inventory. Rates of GBV perpetration were 60.9%, 23.6% and 10.0% for psychological abuse, non-sexual physical violence and sexual violence, respectively. GBV perpetration was associated with higher depression, higher anxiety, lower self-esteem and lower social support. CONCLUSIONS: Interventions to address GBV need to take modifiable individual-level factors into account.

Flexible, phase-transfer catalyzed approaches to 4-substituted prolines.

A range of 4-substituted prolines can be rapidly synthesized from a protected glycine Schiff base in only four steps and in 27-55% overall yield. Phase transfer catalysis allows direct access to both enantiomeric series, and the relative stereochemistry at the 4-position is readily controlled (>10:1 dr) through the choice of hydrogenation conditions.

Diversity oriented synthesis: a challenge for synthetic chemists.

This article covers the diversity-oriented synthesis (DOS) of small molecules in order to generate a collection of pure compounds that are attractive for lead generation in a phenotypic, high-throughput screening approach useful for chemical genetics and drug discovery programmes. Nature synthesizes a rich structural diversity of small molecules, however, unfortunately, there are some disadvantages with using natural product sources for diverse small-molecule discovery. Nevertheless we have a lot to learn from nature. The efficient chemical synthesis of structural diversity (and complexity) is the aim of DOS. Highlights of this article include a discussion of nature's and synthetic chemists' strategies to obtain structural diversity and an analysis of molecular descriptors used to classify compounds. The assessment of how successful one diversity-oriented synthesis is vs another is subjective; therefore we use freely available software (www.cheminformatics.org/diversity) to assess structural diversity in any combinatorial synthesis.

Pneumonectomy: review of 351 cases.

Among 351 patients undergoing pneumonectomy, the mortality was 6%, and when the operation was performed for malignant disease, the mortality was 8.5%. Much of the risk of the operation is associated with the age, physiologic state, and associated diseases which are prevalent in patients who require pneumonectomy. The conduct of the operative procedure itself is of paramount importance since complications clearly increase the mortality. Operative mishaps predispose to postoperative complications, and the addition of postoperative problems to the operative complications combine to bring the mortality to 24%. Careful hemostasis, meticulous technique, fluid and blood replacement, as well as careful preoperative and postoperative management combine to produce an acceptable mortality in this serious procedure.