New Bio-Based Furanic Materials Effectively Absorb Metals from Water and Exert Antimicrobial Activity

Development of sustainable bio-based materials for removal of toxic contaminants from water is a high priority goal. Novel bio-based binary and ternary copolymers with enhanced ion-exchange, adsorption and antibacterial properties were obtained by using plant biomass-derived diallyl esters of furandicarboxylic acid (FDCA) as crosslinking agents and easily available vinyl monomers. The synthesized copolymer materials showed higher sorption capacities for Ni^II, Co^II and Cu^II compared to the commercial ion-exchange resins, and they maintained their high metal adsorption capacities for over 10 cycles of regeneration. The synthesized copolymer gels containing 1–5 wt % of the crosslinker showed excellent water absorption capacities. The synthesized copolymers with 1 % crosslinker content showed swelling ratios high enough to also act as moisture absorbents. Synthesized copolymers with crosslinker content of 10 wt % performed as contact-active antibacterials by inhibiting the growth of Gram-positive (S. aureus) and Gram-negative bacteria (E. coli, K. pneumonia) in suspension tests.     

The highly stereoselective decarboxylation of (+)-1-bromo-1-chloro-2,2,2-trifluoropropanoic acid to give (+)-1-bromo-1-chloro-2,2,2-trifluoroethane [(+)-halothane] with retention of configuration

The absolute configuration of the title acid 2 has been determined to be S by X-ray crystallography. Thus, decarboxylation of 2 produces (S)-(+)-halothane with 99% retention of configuration. This behavior is compared to other stereoselective decarboxylation reactions of α-haloacids from the literature that also gave high degrees of retention of configuration when in the form of their quaternary ammonium salts, which contain one proton. The proton of the ammonium salt is necessary in order to protonate the anionic intermediate formed from decarboxylation. In the absence of this relatively acidic proton, we had previously found that using triethylene glycol (TEG) as both the solvent and proton source for the decarboxylation reaction of acid 2 caused poor stereoselectivity. This was in contrast to 1,2,2,2-tetrafluoro-1-methoxypropionic acid 6, which showed a high degree of retention of configuration in TEG. In order to rationalize this differing behavior, we report DFT studies at PCM-B3LYP/6-31++G⁷ level of theory (the results were additionally confirmed with 6-311++G⁷ and aug-cc-pVDZ basis sets). The energy barrier to inversion of configuration of the anionic reaction intermediate 11 of acid 2 is 10.23 kcal/mol. However, we find that the anionic intermediate 10 from acid 6 would rather undergo β-elimination instead of inversion of configuration. Thus the planar transition state required for inversion of configuration is never reached, regardless of the rate of proton transfer to the anion.     

From data to knowledge—Use of the Cambridge Structural Database for studying molecular interactions

Abstract

The ordered arrangement of molecules and ions in crystal structures is the result of non-bonded interactions, albeit modulated in the crystalline state by random crystal packing forces. Each individual crystal structure gives but a snapshot of these interactions. It is only by examining a large number of structures containing similar molecules or functional groups that we can gain any generalized knowledge about the rules governing molecular interactions. Indeed if we knew these rules it should be possible to predict crystal structures likely to be formed by specific molecules, whereas at present each new crystal structure requires a de novo experimental solution. We would also be able to evaluate the relative contribution of non-bonded and crystal packing forces and extrapolate to the interactive behaviour of molecules in solution and, most importantly, in the environments encountered in biological systems. A key to these studies is the Cambridge Structural Database (CSD) system where experimental results from over 100,000 individual structure determinations are stored in computer readable form. The system also provides the computational tools needed to locate the relevant structures and analyse the numerical data using a variety of statistical techniques. This paper describes the latest Version of the CSD system (Version 5) released Autumn 1992. The use of the system is illustrated by several examples, such as the preferential interaction of certain functional groups, the study of the C—H…O bond and drug-DNA interactions.     

The Thermodynamics of Translesion DNA Synthesis Past Major Adducts of Enantiomeric Analogues of Antitumor Cisplatin

The Pt^II-coordination complex [PtCl₂(DAB)] (DAB=2,3-diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged-DNA-processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2-d(GG) intrastrand cross-link formed by the R,R and S,S enantiomers of [Pt(DAB)]²⁺ in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication-bypass past 1,2-d(GG) adducts of the [Pt(DAB)]²⁺ enantiomers. In the sequence TGGT, the 1,2-d(GG) intrastrand cross-links that were formed by the enantiomeric pairs of [Pt(DAB)]²⁺ inhibited DNA polymerization in a chirality-dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt-d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum-coordinated compounds on the processing of these lesions by damaged-DNA processing-enzymes.     

Atomic force microscopy characterization of β-casein nanoparticles on mica and graphite

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The thermal behavior of double complex compounds with the cation [Cr(ur)6]3+ in a reducing atmosphere

Journal of Thermal Analysis and Calorimetry - The thermal behavior of double complex compounds (DCC) [Cr(ur)6][Co(CN)6]·4H2O (I), [Cr(ur)6][Co(C2O4)3]·3.5H2O (II),...     

A Curtin–Hammett pentamethylene chain symmetrization process in the Bergman cyclization of an 11‐membered ring enediyne

Pentamethylene chain conformational effects for the Bergman cyclization of the 11‐membered ring enediyne, (3Z)‐3‐cycloundecene‐1,5‐diyne, 2, are examined theoretically with unrestricted Becke, three‐parameter, Lee–Yang–Parr/6‐31 G(d,p) calculations. A C₁ symmetric enediyne conformation was found to be the global minimum, where its nonsymmetric pentamethylene chain prevented π‐orbital alignment of the acetylene groups for C–C σ bond product formation. The Bergman cyclization of 2 was found to be conformationally dependent. In a Curtin–Hammett type process, the C₁ symmetric 2 inverts to one of the C_S or C₂ symmetric conformers required for the Bergman cyclization, which produced a C_S or C₂ symmetric 1,4‐diradical intermediate. The activation energy for the cyclization is slightly higher to reach the C₂ symmetry diradical compared with the C_S symmetry diradical. Copyright © 2012 John Wiley & Sons, Ltd.     

Fluorinated 1,3-benzothiazin-4-ones containing fluoroquinolone fragment

Chemistry of Heterocyclic Compounds - We have developed an efficient synthetic approach to potential antibacterial agents with double mechanism of action through the combination of antibacterial...