The defensin–lipid interaction: Insights on the binding states of the human antimicrobial peptide HNP-1 to model bacterial membranes

Antimicrobial peptides are an important component of innate immunity and have generated considerable interest as a new potential class of natural antibiotics. The biological activity of antimicrobial peptides is strongly influenced by peptide–membrane interactions. Human Neutrophil Peptide 1 (HNP-1) is a 30 aminoacid peptide, belonging to the class of α-defensins. Many biophysical studies have been performed on this peptide to define its mechanism of action. Combining spectroscopic and thermodynamic analysis, insights on the interaction of the α-defensin with POPE:POPG:CL negative charged bilayers are given. The binding states of the peptide below and above the threshold concentration have been analyzed showing that the interaction with lipid bilayers is dependent by peptide concentration. These novel results that indicate how affinity and biological activities of natural antibiotics are depending by their concentration, might open new way of investigation of the antimicrobial mode of action.     

Long-lasting inhibition of EGFR autophosphorylation in A549 tumor cells by intracellular accumulation of non-covalent inhibitors

In the present study, a small set of reversible or irreversible 4-anilinoquinazoline EGFR inhibitors was tested in A549 cells at early (1 h) and late (8 h) time points after inhibitor removal from culture medium. A combination of assays was employed to explain the observed long-lasting inhibition of EGFR autophosphorylation. We found that EGFR inhibition at 8 h can be due, besides to the covalent interaction of the inhibitor with Cys797, as for PD168393 (2) and its prodrug 4, to the intracellular accumulation of non-covalent inhibitors by means of an active cell uptake, as for 5 and 6. Compounds 5–6 showed similar potency and duration of inhibition of EGFR autophosphorylation as the covalent inhibitor 2, while being devoid of reactive groups forming covalent bonds with protein thiols.     

Culex pipiens Development Is Greatly Influenced by Native Bacteria and Exogenous Yeast

Culex pipiens is the most cosmopolitan mosquito of the Pipiens Assemblage. By studying the nature of interactions between this species and microorganisms common to its breeding environment we can unravel important pitfalls encountered during development. We tested the survival rate of larval stages, pupae and adults of a Cx. pipiens colony exposed to a variety of microorganisms in laboratory conditions and assessed the transmission to offspring (F1) by those organisms that secured development up to adulthood. Three complementary experiments were designed to: 1) explore the nutritional value of yeasts and other microorganisms during Cx. pipiens development; 2) elucidate the transstadial transmission of yeast to the host offspring; and 3) to examine the relevance of all these microorganisms in female choice for oviposition-substratum. The yeast Saccharomyces cerevisiae proved to be the most nutritional diet, but despite showing the highest survival rates, vertical transmission to F1 was never confirmed. In addition, during the oviposition trials, none of the gravid females was attracted to the yeast substratum. Notably, the two native bacterial strains, Klebsiella sp. and Aeromonas sp., were the preferred oviposition media, the same two bacteria that managed to feed neonates until molting into 2^nd instar larvae. Our results not only suggest that Klebsiella sp. or Aeromonas sp. serve as attractants for oviposition habitat selection, but also nurture the most fragile instar, L1, to assure molting into a more resilient stage, L2, while yeast proves to be the most supportive diet for completing development. These experiments unearthed survival traits that might be considered in the future development of strategies of Cx. pipiens control. These studies can be extended to other members of the Pipiens Assemblage.     

Transferability of Material Composition Indicators for Residential Buildings: A Conceptual Approach Based on a German‐Japanese Comparison

Most anthropogenic material stocks and flows are associated with the building sector. Several recent studies have developed material composition indicators (MCIs) suitable for calculating material stocks and flows of the building sector using bottom‐up approaches, which hold great potential to provide information to support resource efficiency policies. A major limitation is the lack of country‐specific MCIs. This study aims to introduce a concept for a better transferability of MCI across different contexts by proposing requirements for defining MCIs and to discuss options and limits of the transferability. We take existing MCIs for residential buildings in Germany and Japan as case studies and make them comparable by applying harmonization methods. Based on that, similarities and differences are systematically identified and discussed, considering their socioeconomic, cultural, technical, and environmental factors. Our results indicate significant limitations to the transferability of MCIs for detached houses, while bigger apartment complexes show greater homogeneity despite the very different environments in which they are constructed. This indicates that while it is possible to assume foreign MCIs as plausible for large constructions, local coefficients need to be estimated for smaller single‐family homes.     

Quality Assessment and Circularity Potential of Recovery Systems for Household Plastic Waste

Plastic recycling is promoted in the transition toward a circular economy and a closed plastic loop, typically using mass‐based recycling targets. Plastic from household waste (HHW) is contaminated and heterogeneous, and recycled plastic from HHW often has a limited application range, due to reduced quality. To correctly assess the ability to close plastic loops via recycling, both plastic quantities and qualities need to be evaluated. This study defines a circularity potential representing the ability of a recovery system to close material loops assuming steady‐state market conditions. Based on an average plastic waste composition including impurities, 84 recovery scenarios representing a wide range of sorting schemes, source‐separation efficiencies, and material recovery facility (MRF) configurations and performances were assessed. The qualities of the recovered fractions were assessed based on contamination and the circularity potential calculated for each scenario in a European context. Across all scenarios, 17% to 100% of the generated plastic mass could be recovered, with higher source‐separation and MRF efficiencies leading to higher recovery. Including quality, however, at best 55% of the generated plastic was suitable for recycling due to contamination. Source‐separation, a high number of target fractions, and efficient MRF recovery were found to be critical. The circularity potential illustrated that less than 42% of the plastic loop can be closed with current technology and raw material demands. Hence, Europe is still far from able to close the plastic loop. When transitioning toward a circular economy, the focus should be on limiting impurities and losses through product design, technology improvement, and more targeted plastic waste management.     

Identification and characterization of carbapenem binding sites within the RND-transporter AcrB

Understanding the molecular determinants for recognition, binding and transport of antibiotics by multidrug efflux systems is important for basic research and useful for the design of more effective antimicrobial compounds. Imipenem and meropenem are two carbapenems whose antibacterial activity is known to be poorly and strongly affected by MexAB-OprM, the major efflux pump transporter in Pseudomonas aeruginosa. However, not much is known regarding recognition and transport of these compounds by AcrAB-TolC, which is the MexAB-OprM homologue in Escherichia coli and by definition the paradigm model for structural studies on efflux pumps. Prompted by this motivation, we unveiled the molecular details of the interaction of imipenem and meropenem with the transporter AcrB by combining computer simulations with biophysical experiments. Regarding the interaction with the two main substrate binding regions of AcrB, the so-called access and deep binding pockets, molecular dynamics simulations revealed imipenem to be more mobile than meropenem in the former, while comparable mobilities were observed in the latter. This result is in line with isothermal titration calorimetry, differential scanning experiments, and binding free energy calculations, indicating a higher affinity for meropenem than imipenem at the deep binding pocket, while both sharing similar affinities at the access pocket. Our findings rationalize how different physico-chemical properties of compounds reflect on their interactions with AcrB. As such, they constitute precious information to be exploited for the rational design of antibiotics able to evade efflux pumps.     

The status of research on the mammals of Sulawesi,Indonesia

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2-Aminobenzoxazole-appended coumarins as potent and selective inhibitors of tumour-associated carbonic anhydrases

We have carried out the design, synthesis, and evaluation of a small library of 2-aminobenzoxazole-appended coumarins as novel inhibitors of tumour-related CAs IX and XII. Substituents on C-3 and/or C-4 positions of the coumarin scaffold, and on the benzoxazole moiety, together with the length of the linker connecting both units were modified to obtain useful structure-activity relationships. CA inhibition studies revealed a good selectivity towards tumour-associated CAs IX and XII (K_i within the mid-nanomolar range in most of the cases) in comparison with CAs I, II, IV, and VII (K_i > 10 µM); CA IX was found to be slightly more sensitive towards structural changes. Docking calculations suggested that the coumarin scaffold might act as a prodrug, binding to the CAs in its hydrolysed form, which is in turn obtained due to the esterase activity of CAs. An increase of the tether length and of the substituents steric hindrance was found to be detrimental to in vitro antiproliferative activities. Incorporation of a chlorine atom on C-3 of the coumarin moiety achieved the strongest antiproliferative agent, with activities within the low micromolar range for the panel of tumour cell lines tested.