Redox- and glucose-responsive hydrogels from poly(vinyl alcohol) and 4-mercaptophenylboronic acid

Novel redox- and glucose-responsive hydrogels have been synthesized by simple mixing of poly(vinyl alcohol) (PVA) and 4-mercaptophenylboronic acid (MPBA) in aqueous solutions (pH > 9) in an oxidative aqueous media. These hydrogels are produced through the formation of disulfide linkages between MPBA molecules in an oxidative environment (oxygen dissolved in solution or hydrogen peroxide added to the reaction mixture) and complexation via dynamic covalent bonds between PVA and MPBA dimer. These hydrogels show degradation in solutions of l-glutathione and d-glucose.

3-5-Man chess data

This reports the work of Karrer and Wirth in identifying percentage results and, respectively, the Depth to Mate (DTM) and Depth to Conversion (DTC) data in all 2-5-man chess endgames.

3-5-man mutual zugzwangs in chess

This note reports the work of Wirth and Karrer in twin-sourcing all mutual zugzwang positions, mzugs, in 2-5-man endgames. This paper tabulates the mzug statistical data, gives examples of maximal mzugs and refers to a chess endgame website where further data is to be found.

trans-[Ru-III(N-N)(2)Cl-2](+) species, where N-N is bis(3,5-dimethylpyrazol-1-yl)methane

Using bis(3,5-dimethylpyrazol-1-yl)methane as an N-N donor ligand, a trans-[Ru-III(N-N)(2)Cl-2](+) core has been isolated from the direct reaction of the ligand with RuCl3 center dot xH(2)O and characterized structurally for the. first time. The core displays a rhombic EPR spectrum and a quasireversible Ru(II/III) couple with an E-1/2 of -0.34 V versus NHE. (C) 2008 Elsevier B.V. All rights reserved.

Carbanucleosides: synthesis of both enantiomers of 2-(6-chloro-purin-9-yl)-3,5-bishydroxymethyl cyclopentanol from D-glucose

The key intermediate 1,2:5,6-di-O-isopropylidene-3-deoxy-3 beta-allyl-alpha-D-glucofuranose (8) could be conveniently prepared through radical induced allyl substitution at C-3 of appropriate 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose derivatives (7a,b) and used to synthesize enantiomeric bishydroxymethyl aminocyclopentanols 13 and 19 by the application of a 1,3-dipolar nitrone cycloaddition reaction involving the C-5 or C-1 aldehyde functionality. The products were subsequently transformed into carbanucleoside enantiomers 15 and 21. The diastercomeric isoxazolidinocyclopentane derivative 20 was similarly converted to carbanucleoside 22. (c) 2006 Elsevier Ltd. All rights reserved.

Trapping of palindromic ligands within native transthyretin prevents amyloid formation

Transthyretin (TTR) amyloidosis is a fatal disease for which new therapeutic approaches are urgently needed. We have designed two palindromic ligands, 2,2’-(4,4’-(heptane 1,7-diylbis(oxy))bis(3,5-dichloro-4,1-phenylene)) bis(azanediyl)dibenzoic acid (mds84) and 2,2’-(4,4’-(undecane-1,11-diylbis(oxy))bis(3,5-dichloro-4,1-phenylene)) bis(azanediyl)dibenzoic acid (4ajm15), that are rapidly bound by native wild-type TTR in whole serum and even more avidly by amyloidogenic TTR variants. One to one stoichiometry, demonstrable in solution and by MS, was confirmed by X-ray crystallographic analysis showing simultaneous occupation of both T4 binding sites in each tetrameric TTR molecule by the pair of ligand head groups. Ligand binding by native TTR was irreversible under physiological conditions, and it stabilized the tetrameric assembly and inhibited amyloidogenic aggregation more potently than other known ligands. These superstabilizers are orally bioavailable and exhibit low inhibitory activity against cyclooxygenase (COX). They offer a promising platform for development of drugs to treat and prevent TTR amyloidosis.

Excited states of nitro-polypyridine metal complexes and their ultrafast decay. Time-resolved IR absorption, spectroelectrochemistry, and TD-DFT calculations of fac-[Re(Cl)(CO)3(5-Nitro-1,10-phenanthroline)]

The lowest absorption band of fac-[Re(Cl)(CO)(3)(5-NO2-phen)] encompasses two close-lying MLCT transitions. The lower one is directed to LUMO, which is heavily localized on the NO2 group. The UV-vis absorption spectrum is well accounted for by TD-DFT (G03/PBEPBE1/CPCM), provided that the solvent, MeCN, is included in the calculations. Near-UV excitation of fac-[Re(Cl)(CO)(3)(5-NO2-phen)] populates a triplet metal to ligand charge-transfer excited state, (MLCT)-M-3, that was characterized by picosecond time-resolved IR spectroscopy. Large positive shifts of the v(CO) bands upon excitation (+70 cm(-1) for the A'(1) band) signify a very large charge separation between the Re(Cl)(CO)3 unit and the 5-NO2-phen ligand. Details of the excited-state character are revealed by TD-DFT calculated changes of electron density distribution. Experimental excited-state v(CO) wavenumbers agree well with those calculated by DFT. The (MLCT)-M-3 state decays with a ca. 10 ps lifetime (in MeCN) into another transient species, that was identified by TRIR and TD-DFT calculations as an intraligand (3)n pi* excited state, whereby the electron density is excited from the NO2 oxygen lone pairs to the pi* system of 5-NO2-phen. This state is short-lived, decaying to the ground state with a similar to 30 ps lifetime. The presence of an n pi* state seems to be the main factor responsible for the lack of emission and the very short lifetimes of 3 MLCT states seen in all d(6)-metal complexes of nitro-polypyridyl ligands. Localization of the excited electron density in the lowest (MLCT)-M-3 states parallels localization of the extra electron in the reduced state that is characterized by a very small negative shift of the v(CO) IR bands (-6 cm(-1) for A'(1)) but a large downward shift of the v(s)(NO2) IR band. The Re-Cl bond is unusually stable toward reduction, whereas the Cl ligand is readily substituted upon oxidation.

Rhenium-to-benzoylpyridine and rhenium-to-bipyridine MLCT excited states offac-[Re(Cl)(4-benzoylpyridine)2(CO)3] andfac-[Re(4-benzoylpyridine)(CO)3(bpy)]+: a time-resolved spectroscopic and spectroelectrochemical study

The lowest allowed electronic transition of fac-[Re(Cl)(CO)(3)(bopy)(2)] (bopy = 4-benzoylpyridine) has a Re --> bopy MLCT character, as revealed by UV-vis and stationary resonance Raman spectroscopy. Accordingly, the lowest-lying, long-lived, excited state is Re --> bopy (MLCT)-M-3. Electronic depopulation of the Re(CO)(3) unit and population of a bopy pi* orbital upon excitation are evident by the upward shift of v(Cequivalent toO) vibrations and a downward shift of the ketone v(C=O) vibration, respectively, seen in picosecond time-resolved IR spectra. Moreover, reduction of a single bopy ligand in the (MLCT)-M-3 excited state is indicated by time-resolved visible and resonance Raman (TR3) spectra that show features typical of bopy(.-). In contrast, the lowest allowed electronic transition and lowest-lying excited state of a new complex fac-[Re(bopy)(CO)(3)(bpy)](+) (bpy = 2,2'-bipyridine) have been identified as Re --> bpy MLCT with no involvement of the bopy ligand, despite the fact that the first reduction of this complex is bopy-localized, as was proven spectroelectrochemically. This is a rare case in which the localizations of the lowest MLCT excitation and the first reduction are different. (MLCT)-M-3 excited states of both fac-[Re(Cl)(CO)(3)(bopy)(2)] and fac-[Re(bopy)(CO)(3)(bpy)](+) are initially formed vibrationally hot. Their relaxation is manifested by picosecond dynamic shifts of v(Cequivalent toO) IR bands. The X-ray structure of fac-[Re(bopy)(CO)(3)(bpy)](PF6CH3CN)-C-. has been determined.

Synthesis, chemical, electrochemical characterization of oxomolybdenum(V) complexes of 2-(3,5-dimethyl pyrazol-1-yl) benzothiazole ligand: crystal structure of ligand and oxomolybdenum(VI) complex and density functional theory (DFT) calculation

This work reports the ligational behavior of the neutral bidentate chelating molecule 2-(3,5-dimethyl pyrazol-1-yl) benzothiazole towards the oxomolybdenum(V) center. Both mononuclear complexes of the type (MoOX3L)-O-V and binuclear complexes of the formula (Mo2O4X2L2)-O-V (where X = Cl, Br) are isolated in the solid state. The complexes are characterized by elemental analyses, various spectroscopic techniques (UV-Vis IR), magnetic susceptibility measurement at room temperature, and cyclic voltammetry for their redox behavior at a platinum electrode in CH3CN. The mononuclear complexes (MoOX3L)-O-V are found to be paramagnetic while the binuclear complexes Mo2O4X2L2 are diamagnetic. Crystal and molecular structure of the ligand and the dioxomolybdenum complex (MoO2Br2L)-O-VI (obtained from the complex MoOBr3L during crystallization) have been solved by single crystal X-ray diffraction technique. Relevant DFT calculations of the ligand and the complex (MoO2Br2L)-O-VI are also carried out.

Sample preparation: a crucial factor for the analytical performance of rationally designed MALDI matrices

Evidence is presented that the performance of the rationally designed MALDI matrix 4-chloro-α-cyanocinnamic acid (ClCCA) in comparison to its well-established predecessor α-cyano-4-hydroxycinnamic acid (CHCA) is significantly dependent on the sample preparation, such as the choice of the target plate. In this context, it becomes clear that any rational designs of MALDI matrices and their successful employment have to consider a larger set of physicochemical parameters, including sample crystallization and morphology/topology, in addition to parameters of basic (solution and/or gas-phase) chemistry.

Coupling liquid MALDI MS to liquid chromatography

Matrix-assisted laser desorption/ionisation (MALDI) coupled with time-of-flight (TOF) mass spectrometry (MS) is a powerful tool for the analysis of biological samples, and nanoflow high-performance liquid chromatography (nanoHPLC) is a useful separation technique for the analysis of complex proteomics samples. The off-line combination of MALDI and nanoHPLC has been extensively investigated and straightforward techniques have been developed, focussing particularly on automated MALDI sample preparation that yields sensitive and reproducible spectra. Normally conventional solid MALDI matrices such as α-cyano-4-hydroxycinnamic acid (CHCA) are used for sample preparation. However, they have limited usefulness in quantitative measurements and automated data acquisition because of the formation of heterogeneous crystals, resulting in highly variable ion yields and desorption/ ionization characteristics. Glycerol-based liquid support matrices (LSM) have been proposed as an alternative to the traditional solid matrices as they provide increased shot-to-shot reproducibility, leading to prolonged and stable ion signals and therefore better results. This chapter focuses on the integration of the liquid LSM MALDI matrices into the LC-MALDI MS/MS approach in identifying complex and large proteomes. The interface between LC and MALDI consists of a robotic spotter, which fractionates the eluent from the LC column into nanoliter volumes, and co-spots simultaneously the liquid matrix with the eluent fractions onto a MALDI target plate via sheath flow. The efficiency of this method is demonstrated through the analysis of trypsin digests of both bovine serum albumin (BSA) and Lactobacillus plantarum WCFS1 proteins.

Development of novel brush-type chiral stationary phases based on terpenoid selectors: HPLC evaluation and theoretical investigation of enantioselective binding interactions

The terpenoid chiral selectors dehydroabietic acid, 12,14-dinitrodehydroabietic acid and friedelin have been covalently linked to silica gel yielding three chiral stationary phases CSP 1, CSP 2 and CSP 3, respectively. The enantiodiscriminating capability of each one of these phases was evaluated by HPLC with four families of chiral aromatic compounds composed of alcohols, amines, phenylalanine and tryptophan amino acid derivatives and beta-lactams. The CSP 3 phase, containing a selector with a large friedelane backbone is particularly suitable for resolving free alcohols and their derivatives bearing fluorine substituents, while CSP 2 with a dehydroabietic architecture is the only phase that efficiently discriminates 1, 1'-binaphthol atropisomers. CSP 3 also gives efficient resolution of the free amines. All three phases resolve well the racemates of N-trifluoracetyl and N-3,5-dinitrobenzoyl phenylalanine amino acid ester derivatives. Good enantioseparation of beta-lactams and N-benzoyl tryptophan amino acid derivatives was achieved on CSP 1. In order to understand the structural factors that govern the chiral molecular recognition ability of these phases, molecular dynamics simulations were carried out in the gas phase with binary diastereomeric complexes formed by the selectors of CSP 1 and CSP 2 and several amino acid derivatives. Decomposition of molecular mechanics energies shows that van der Waals interactions dominate the formation of the diastereomeric transient complexes while the electrostatic binding interactions are primarily responsible for the enantioselective binding of the (R)- and (S)-analytes. Analysis of the hydrogen bonds shows that electrostatic interactions are mainly associated with the formation of N-(HO)-O-...=C enantio selective hydrogen bonds between the amide binding sites from the selectors and the carbonyl groups of the analytes. The role of mobile phase polarity, a mixture of n-hexane and propan-2-ol in different ratios, was also evaluated through molecular dynamics simulations in explicit solvent. (c) 2006 Elsevier Ltd. All rights reserved.

Short Communication: effects of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester on milk production and composition of lactating Holstein dairy cows

Sixteen multiparous Holstein cows were used to determine the effects of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester (HMBi: 0 vs. 1.26 g/kg of total ration dry matter (DM) and dietary crude protein (CP) concentration [14.7% (low) vs. 16.9% (standard), DM basis] on milk yield and composition using a replicated 4 x 4 Latin square design experiment with 4-wk periods. Cows were fed ad libitum a total mixed ration with a 1: 1 forage-to-concentrate ratio (DM basis), and diets provided an estimated 6.71 and 1.86% lysine and methionine, respectively, in metabolizable protein for the low-protein diet and 6.74 and 1.82% in the standard protein diet. Dry matter intake, milk yield, and composition were measured during wk 4 of each period. There were no effects on DM intake, which averaged 24.7 kg/d. There was an interaction between dietary CP and HMBi for milk yield and 3.5% fat-corrected milk (FCM). Feeding HMBi decreased milk and FCM yield when fed with the low-CP diet but did not affect milk or FCM yield when fed with the standard CP diet. Feeding HMBi increased milk protein concentration regardless of diet CP concentration and increased milk protein yield when added to the standard CP diet but not the low-CP diet. The positive effect of HMBi on milk protein yield was only observed at the standard level of dietary CP, suggesting other factors limited the response to HMBi when dietary protein supply was restricted.