Changes in Ion Selectivity Following the Asymmetrical Addition of Charge to the Selectivity Filter of Bacterial Sodium Channels

Voltage-gated sodium channels (NaVs) play fundamental roles in eukaryotes, but their exceptional size hinders their structural resolution. Bacterial NaVs are simplified homologues of their eukaryotic counterparts, but their use as models of eukaryotic Na⁺ channels is limited by their homotetrameric structure at odds with the asymmetric Selectivity Filter (SF) of eukaryotic NaVs. This work aims at mimicking the SF of eukaryotic NaVs by engineering radial asymmetry into the SF of bacterial channels. This goal was pursued with two approaches: the co-expression of different monomers of the NaChBac bacterial channel to induce the random assembly of heterotetramers, and the concatenation of four bacterial monomers to form a concatemer that can be targeted by site-specific mutagenesis. Patch-clamp measurements and Molecular Dynamics simulations showed that an additional gating charge in the SF leads to a significant increase in Na⁺ and a modest increase in the Ca²⁺ conductance in the NavMs concatemer in agreement with the behavior of the population of random heterotetramers with the highest proportion of channels with charge −5e. We thus showed that charge, despite being important, is not the only determinant of conduction and selectivity, and we created new tools extending the use of bacterial channels as models of eukaryotic counterparts.     

Investigation of intermolecular interactions in solution polymer‐organic dye by method electronic spectroscopy

It has been shown that specific electrostatic interactions between charges of ion dyes and functional groups of polymer play main role in the cause of polar coulored matrices. These interaction prevent by formation tight ion pairs of dyes and their associates. Therefore, such matrices have practically the same electronic spectra as liquid solution of dyes. Electrostatic interactions between dye counterions dominate in low polarity polymer matrices. Process of formation tight ions pair is became easier. Such pairs cause quenching of the fluorescence and distortion of electronic spectra by comparison with liquids.     

Synthesis and Characterization of Biphenylene‐Containing Diazaacenes

We describe the efficient synthesis of substituted benzo[3,4]cyclobuta[1,2‐b]phenazine, benzo[3,4]cyclobuta[1,2]benzo[1,2‐i]phenazine, and benzo[3,4]cyclobuta[1,2‐b]naphtho[2,3‐i]phenazine by a condensation reaction of aromatic diamines with the stable biphenylene‐2,3‐dione.     

Biological activity of selected boronic acids and their derivatives

A series of substituted phenylboronic acids and benzoxaboroles were evaluated for their antimicrobial activity. Antibacterial and antifungal action activity of several compounds was tested against Escherichia coli 67, Staphylococcus aureus 209‐p, Mycobacterium luteum VCM B‐868, Aspergillus niger VCM F‐1119 and Candida tenuis VCM Y‐70. Substituted phenylboronic acids have low biological activity against all the investigated species. Benzoxaboroles reveal higher biological activity in comparison with the corresponding acids. The highest activity was observed for small benzoxaborole molecules, and the unsubstituted benzoxaborole has only slightly lower biological activity as compared with the 5‐fluoro‐substituted one (AN2690). The compound possessing two oxaborole fragments has very high biological activity towards Mycobacterium luteum and both investigated fungi. Copyright © 2012 John Wiley & Sons, Ltd.