Antimicrobial cotton fibres prepared by in situ synthesis of AgCl into a silica matrix

Functional antimicrobial cotton fibres were prepared in a novel two-step procedure utilising the pad-dry-cure method to apply an inorganic–organic hybrid sol–gel precursor (reactive binder, RB) followed by the in situ synthesis of AgCl particles on the RB-treated fibres. The morphology and surface composition of the modified cotton fibres were investigated by scanning electron microscopy imaging and X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy spectral analyses. The bulk concentration of Ag on the cotton fibres was determined by inductively coupled plasma mass spectroscopy, and the antimicrobial activity against the bacteria Escherichia coli and Staphylococcus aureus was estimated according to the ISO 20645:2004 (E) and AATCC 100-1999 methods. The results showed that this application process yields the following important benefits: (1) the presence of the RB silica matrix increased the fibres’ capacity for adsorbing AgCl particles compared with the same fibres without RB; (2) the in situ synthesis enabled a simple and environmentally friendly preparation of AgCl particles from AgNO₃ and their embedment into the fibres; (3) the AgCl particles were bound to the RB silica matrix by physical forces, which allowed for their controlled release from the fibres; (4) the capacity of the RB-modified cotton samples to hold embedded AgCl particles was sufficient to provide a 100 % bacterial reduction even after 10 repeated washing cycles; and (5) the chemical modification of the cotton fibres did not significantly change their whiteness, wettability or softness.     

Non‐enzymatic Ribonucleotide Reduction in the Prebiotic Context

Model studies of prebiotic chemistry have revealed compelling routes for the formation of the building blocks of proteins and RNA, but not DNA. Today, deoxynucleotides required for the construction of DNA are produced by reduction of nucleotides catalysed by ribonucleotide reductases, which are radical enzymes. This study considers potential non‐enzymatic routes via intermediate radicals for the ancient formation of deoxynucleotides. In this context, several mechanisms for ribonucleotide reduction, in a putative H₂S/HS^. environment, are characterized using computational chemistry. A bio‐inspired mechanistic cycle involving a keto intermediate and HSSH production is found to be potentially viable. An alternative pathway, proceeding through an enol intermediate is found to exhibit similar energetic requirements. Non‐cyclical pathways, in which HSS^. is generated in the final step instead of HS^., show a markedly increased thermodynamic driving force (ca. 70 kJ mol^?1) and thus warrant serious consideration in the context of the prebiotic ribonucleotide reduction.     

Optimization Condition for Thin-Layer Identification of Bronzes after Anodic Sampling

JPC – Journal of Planar Chromatography – Modern TLC - Qualitative identification of Cu, Sn, Pb, Ni, and Fe in Cu-alloys is presented. The method involves anodic sampling of alloys,...     

Antitumour tiazofurin analogues embedded with an amide moiety at the C-2′ position

Synthesis of four new tiazofurin analogues has been accomplished starting from d-glucose. The key step of the synthesis was the three-step cascade that enabled an efficient hydrogen sulfide mediated one-pot conversion of 2-azido-3-O-acyl-ribofuranosyl cyanides to the corresponding 2-alkylamido ribofuranosyl thiocarboxamides. The resulting key intermediates were first converted to protected tiazofurin derivatives by cyclocondensation with ethyl bromopyruvate, and finally to target C-nucleosides by treatment with ammonia in methanol. In vitro cytotoxicities of tiazofurin analogues against a number of human tumour cell lines were recorded and compared with those observed for the parent molecule (tiazofurin), as well as the commercial antitumour agent doxorubicin (DOX). Analogues 2b-d have shown a potent in vitro cytotoxic activity against human myelogenous leukaemia K562. Among solid tumour cell lines, HT29 was sensitive only to 2d, while HeLa cells were sensitive to 2a, 2b and 2d. Only analogue 2a was highly cytotoxic against MCF-7 cells. No tiazofurin analogue exhibits any significant cytotoxicity towards normal foetal lung MRC-5 cells. Downregulation of Bcl-2, activation of caspase-3 and presence of cleavage product of PARP suggest that the cytotoxic effects of tiazofurin analogues 2a-d in K562 might be mediated by apoptosis in a caspase-dependent way. On the contrary, tiazofurin did not induce apoptosis of K562 cells, which suggests a different mechanism of action, most probably through the inhibition of IMPDH. Flow cytometry and Western blot analysis data agreed well with the results of MTT assay, and enabled identification of analogue 2c as the most promising antitumour agent that preferentially target cancer cells over normal cells and thus represents a new lead for further optimization.     

2-Substituted thiazole-4-carboxamide derivatives as tiazofurin mimics: synthesis and in vitro antitumour activity

Tiazofurin analogues bearing a 5-hydroxymethyl-2-methyl-tetrahydrofuro[2,3-d][1,3]dioxol-6-ol moiety as a sugar mimic (2 and 3), and two novel thiazole-based acyclo-C-nucleosides 4 and 16 have been synthesized in multistep sequences starting from d-xylose (compounds 2 and 3) or from d-arabinose (compounds 4 and 16). All synthesized analogues showed potent in vitro antitumour activities against a panel of human tumour cell lines. Flow cytometry data suggest that cytotoxic effects of analogues 2–4 and 16 in the culture of K562 cells might be mediated by apoptosis. It was also found that these analogues induced changes in cell cycle distribution of K562 cells. Results of western blot analysis (upregulation of Bax and downregulation of Bcl-2, activation of caspase-3 and the presence of a PARP cleavage product) suggest that tiazofurin mimics (2–4 and 16) in K562 cells induced apoptosis in a caspase-dependent way.     

Mechanical and anti‐stabbing properties of modified thermoplastic polymers impregnated multiaxial p‐aramid fabrics

New forms of hybrid multiaxial nanocomposites with enhanced mechanical and stab resisting properties are presented. This study is motivated by the lack of knowledge in the study of the multiaxial fabric nanocomposites with two modified thermoplastic matrices for antiballistic protection. Introduction of 5 wt.% silica nanoparticles in the composite of polyurethane/p‐aramid/poly (vinyl butyral) leads to significant improvement in mechanical properties, and the addition of silane as a coupling agents and glutaraldehyde as a crosslinking agents yielded maximal values of storage modulus, tensile modulus and anti‐stabbing properties for hybrid nanocomposites. Ballistic resistance testing and penetration depth of the hybrid nanocomposites were visualized using image analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

The Baeyer strain is strongly affected by the nucleus-electron attraction—a comment on the Letter of G. Hohlneicher and L. Packschies [Tetrahedron Lett. 2007, 48, 6429-6433]

The origin of the angular strain is studied in deformed methane and cyclohexane selected as the model systems par excellence. It is shown that the electron correlation contribution to the angular strain is negligible. Analysis of the Hartree-Fock energies provides a convincing evidence that the angular strain is a consequence of the unfavourable nucleus-electron attraction occuring due to bond bending. This should take place in other angularly distorted molecules as a rule. However, other effects might be even more important sometimes. In these cases the V_ne term can serve as a useful diagnostic tool.     

Anodic Sampling and TLC Identification of Dental Alloys

JPC – Journal of Planar Chromatography – Modern TLC - Knowledge of the composition of an incorporated alloy is a precondition for avoiding polymetallism in subsequent prosthetic...     

Quantification of (−)-Epicatechin and Procyanidin B2 in Chocolates

JPC – Journal of Planar Chromatography – Modern TLC - Validation of a method for the quantification of (−)-epicatechin and procyanidin B2 in chocolates is reported. After a simple...