Insect‐Derived Proline‐Rich Antimicrobial Peptides Kill Bacteria by Inhibiting Bacterial Protein Translation at the 70 S Ribosome

Proline‐rich antimicrobial peptides (PrAMPs) have been investigated and optimized by several research groups and companies as promising lead compounds to treat systemic infections caused by Gram‐negative bacteria. PrAMPs, such as apidaecins and oncocins, enter the bacteria and kill them apparently through inhibition of specific targets without a lytic effect on the membranes. Both apidaecins and oncocins were shown to bind with nanomolar dissociation constants to the 70S ribosome. In apidaecins, at least the two C‐terminal residues (Arg17 and Leu18) interact strongly with the 70S ribosome, whereas residues Lys3, Tyr6, Leu7, and Arg11 are the major interaction sites in oncocins. Oncocins inhibited protein biosynthesis very efficiently in vitro with half maximal inhibitory concentrations (IC₅₀ values) of 150 to 240 nmol L ^?1. The chaperone DnaK is most likely not the main target of PrAMPs but it binds them with lower affinity.     

Exploring the Bile Stress Response of Lactobacillus mucosae LM1 through Exoproteome Analysis

Lactobacillus sp. have long been studied for their great potential in probiotic applications. Recently, proteomics analysis has become a useful tool for studies on potential lactobacilli probiotics. Specifically, proteomics has helped determine and describe the physiological changes that lactic acid bacteria undergo in specific conditions, especially in the host gut. In particular, the extracellular proteome, or exoproteome, of lactobacilli contains proteins specific to host– or environment–microbe interactions. Using gel-free, label-free ultra-high performance liquid chromatography tandem mass spectrometry, we explored the exoproteome of the probiotic candidate Lactobacillus mucosae LM1 subjected to bile treatment, to determine the proteins it may use against bile stress in the gut. Bile stress increased the size of the LM1 exoproteome, secreting ribosomal proteins (50S ribosomal protein L27 and L16) and metabolic proteins (lactate dehydrogenase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase and pyruvate dehydrogenases, among others) that might have moonlighting functions in the LM1 bile stress response. Interestingly, membrane-associated proteins (transporters, peptidase, ligase and cell division protein ftsH) were among the key proteins whose secretion were induced by the LM1 bile stress response. These specific proteins from LM1 exoproteome will be useful in observing the proposed bile response mechanisms via in vitro experiments. Our data also reveal the possible beneficial effects of LM1 to the host gut.     

Total Synthesis and Activity of the Metallo‐β‐lactamase Inhibitor Aspergillomarasmine A

Resistance to β‐lactam antibiotics is mediated primarily by enzymes that hydrolytically inactivate the drugs by one of two mechanisms: serine nucleophilic attack or metal‐dependent activation of a water molecule. Serine β‐lactamases are countered in the clinic by several codrugs that inhibit these enzymes, thereby rescuing antibiotic action. There are no equivalent inhibitors of metallo‐β‐lactamases in clinical use, but the fungal secondary metabolite aspergillomarasmine A has recently been identified as a potential candidate for such a codrug. Herein we report the synthesis of aspergillomarasmine A. The synthesis enabled confirmation of the stereochemical configuration of the compound and offers a route for the synthesis of derivatives in the future.     

Multi‐Input/Multi‐Output Molecular Response System Based on the Dynamic Redox Behavior of 3,3,4,4‐Tetraaryldihydro[5]helicene Derivatives: Reversible Formation/Destruction of Chiral Fluorophore and Modulation of Chiroptical Properties by Solvent Polarity

3,3,4,4‐Tetaaryldihydro[5]helicenes ( 1 ) and 1,1′‐binaphthyl‐2,2′‐diylbis(diarylcarbenium)s ( 2 ²⁺) can be reversibly interconverted upon electron transfer, which is accompanied by a vivid color change (electrochromism) as well as by the formation/cleavage of a C? C bond (“dynamic redox behavior”). Because only the neutral donor 1 exhibits strong fluorescence, electrochemical input can further modify the fluorescent properties of the pair. Due to the configurational stability of the helicity in 1 and axial chirality in 2 ²⁺, the redox reaction of optically pure material proceeds stereospecifically, which induces a chiroptical change such as circular dichroism (CD) as an additional output. The CD spectra of dications 2 ²⁺ exhibit solvent dependency (chiro‐solvatochromism), which is accompanied by solvatochromic behavior based on the π–π interaction of the two cationic chromophores as well as coordinative interaction of the Lewis basic solvent to the Lewis acidic triarylcarbenium moieties. Thus, the present system is endowed with multi‐input functionality for modifying multiple output signals.