Three coordination polymers of 5-aminoisophthalic acid with similar benzimidazole derivative ligands: synthesis,structure and DNA-binding studies

Three novel coordination polymers, [Co(NH₂-Aip)(H₂Bibim)] _n (1), [Co(NH₂-Aip)(HBibimop)] _n  √ nH₂O (2) and [Mn(NH₂-Aip) √ H₂O] _n  √ 2nH₂O (3) with NH₂-Aip and similar benzimidazole derivative ligands (NH₂-Aip = 5-aminoisophthalic acid, H₂Bibim = 2,2′-bibenzimidazole and HBibimop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane), have been synthesised under hydrothermal conditions and structurally characterised by single-crystal X-ray diffraction analysis, elemental analysis and IR spectroscopy. 5-Aminoisophthalic acid ligand adopts μ₂-, μ₃- and μ₄-bridge coordination fashion and benzimidazole derivatives exist as terminal- and bridge-mode in complexes 1–3. The intricate hydrogen bonds and π–π stacking interactions in supramolecular framework are discussed. Using the combination of ultraviolet–visible absorption titration and fluorescence spectra, the experimental results show that complexes 1 and 2 bind to DNA in an intercalative mode and their DNA-binding constants (K _b ) are also found.     

An approach to the Paal–Knorr pyrroles synthesis in the presence of β-cyclodextrin in aqueous media

An efficient and facile method for the synthesis of N-substituted pyrroles in moderate to good yields by the Paal–Knorr reaction of γ-diketones with amines in the presence of β-cyclodextrin in aqueous media has been developed.Moreover,this process tolerated diamines(e.g.,para-,meta- or orthophenylenediamine)to construct bis-pyrrole or mono-pyrrole derivates.β-Cyclodextrin can be recovered easily after the reactions and reused without evident loss in activity.     

Incorporation of azide sugar analogue decreases tumorigenic potential of breast cancer cells by reducing cancer stem cell population

The azido sugar,GalNAz,was successfully used for imaging and perturbing protein glycosylation in triple-negative breast cancer cell line,MDA-MB-231.After the incorporation of GalNAz in the triple-negative breast cancer cell line,the tumorigenicity of these cells was decreased.Results from gene analysis and drug treatment suggest that the tumorigenicity decrease may be attributed to the reduction of cancer stem cell population.Possible mechanisms of GalNAz induced cancer stem cells(CSCs) proportion change are discussed.     

Synthesis and Anti‐HIV Activity of Triazolo‐Fused 2′,3′‐Cyclic Nucleoside Analogs Prepared by an Intramolecular Huisgen 1,3‐Dipolar Cycloaddition

Triazolo‐fused 2′,3′‐cyclic nucleoside analogs were synthesized by an intramolecular 1,3‐dipolar cycloaddition of nucleoside‐derived azido alkynes in a regio‐ and stereospecific manner. The uracil base in these target compounds was successfully transformed to the corresponding cytosine. The synthesized compounds were examined in a MAGI assay for their anti‐HIV activities, and in a H9 T lymphocytes assay for their cell toxicities.     

One-Pot Synthesis of Cefpirome Sulfate from GCLE

Abstract

Cefpirome was synthesized in 37.7% overall yield from 3-chloromethyl-7-phenylacetylamino cephalosporanic acid p-methoxybenzyl ester (GCLE) by sequential substitution of C-3 chloride with iodide and 2,3-cyclopentenopyridine, followed by a one-pot procedure including deprotection of carboxyl group, hydrolysis of 7-phenylacetamido, and reaction with 2-mercaptobenzothiazolyl-(Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetate (MAEM). The reaction conditions were as follows: obtained from GCLE at low temperature (?5 to 0 °C) and absence of light, 3-iodomethyl-7-phenylacetylamino cephalosporanic acid p-methoxybenzyl ester (GILE) without purification was reacted directly with 2,3-cyclopentenopyridine, in which the molar ratio of GCLE, NaI, and 2,3-cyclopentenopyridine was 1:2:4, and the molar ratio of the resulting compound p-methoxybenzyl 7-phenylacetylamido-3-(2,3-cyclopenteno-1-pyridinio)methyl-3-cephem-4-carboxylate iodide and MAEM was 1:1.1. The structure of the intermediate and the target compound obtained were determined by nuclear magnetic resonance spectra and mass spectroscopy.     

Fluorescent staining of protein in SDS polyacrylamide gels by salicylaldehyde azine

As a noncovalent fluorescence probe, in this study, salicylaldehyde azine (SA) was introduced as a sensitive fluorescence‐based dye for detecting proteins both in 1D and 2D polyacrylamide electrophoresis gels. Down to 0.2 ng of single protein band could be detected within 1 h, which is similar to that of glutaraldehyde‐silver stain, but approximately four times higher than that of SYPRO Ruby fluorescent stain. Furthermore, comparative analysis of the MS compatibility of SA stain with SYPRO Ruby stain indicated that SA stain is compatible with the downstream of protein identification by LC‐MS/MS. Additionally, the probable mechanism of the SA stain was investigated by molecular docking. The results demonstrated that the interaction between SA and protein was mainly contributed by hydrogen bonding and hydrophobic forces.     

Preparation and characterization of a polystyrene/bovine serum albumin nanoparticle‐coated capillary for chiral separation using open‐tubular capillary electrochromatography

Polystyrene (PS) nanoparticles coated by BSA, hereafter denoted as PS/BSA, were prepared and chemically immobilized for the first time onto a capillary inner wall for open‐tubular CEC (OTCEC). EOF and scanning electron micrography were used to characterize the prepared nanoparticle‐coated capillaries. To investigate the performance of the prepared columns in OTCEC, chiral separation of d ,l ‐tryptophan (dl ‐Trp) was performed in monolayer BSA‐modified capillary and PS/BSA nanoparticle‐coated columns. The results indicated that the nanoparticle‐modified column afforded a higher resolution compared with the monolayer type. Rapid enantioseparation of dl ‐Trp (within 3 min) was achieved with the PS/BSA‐immobilized column using an electroosmotic pump‐assisted CEC. Enantiomer separations of other compounds like dl ‐tyrosine and warfarin were also achieved with the column. Besides, run‐to‐run and column‐to‐column repeatabilities of the PS/BSA‐coated column in the chiral separation were systematically introduced.     

A numerically stable restrained electrostatic potential charge fitting method

Inspired by the idea of charge decomposition in calculation of the dipole preserving and polarization consistent charges (Zhang et al., J. Comput. Chem. 2011, 32, 2127), we have proposed a numerically stable restrained electrostatic potential (ESP)‐based charge fitting method for protein. The atomic charge is composed of two parts. The dominant part is fixed to a predefined value (e.g., AMBER charge), and the residual part is to be determined by restrained fitting to residual ESP on grid points around the molecule. Nonuniform weighting factors as a function of the dominant charge are assigned to the atoms. Because the residual part is several folds to several orders smaller than the dominant part, the impact of ill‐conditioning is alleviated. This charge fitting method can be used in quantum mechanical/molecular mechanical (QM/MM) simulations and similar studies, where QM calculated electronic properties are frequently mapped to partial atomic charges. © 2012 Wiley Periodicals, Inc.     

Liquid crystalline properties of dissymmetric molecules IV. The substituent effect on thermal properties of nematic and smectic A phases in three aromatic ring systems with ester linkages

This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH₃, CH₃, OC₈H₁₇, C8H17, halogens, CF₃, OCF₃, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis.