Hydroxoaquotetraminecobalt(III)-promoted hydrolysis of pyrophosphate. Mechanistic considerations

The hydrolysis of pyrophosphate was investigated at two different concentrations (10^–2 and 10^–3M) of [N₄Co(H₂O)(OH)]²⁺ [N₄=tn₂ or trpn (tn=trimethylenediamine, trpn=tris(3-aminopropyl)amine)] using two quenching methods (Eu^II/H⁺ and OH^–). The reaction was monitored by measurement of orthophosphate (Pi) in quenched aliquots of a reaction mixture consisting of the reagents added to a reaction mixture consisting of the reagents added to a preformed 1:1 pyrophosphate complex (tn₂CoPPi). The results are compared with similar findings in the literature for cyanide-quenched reaction mixtures. The reactive species with regard to hydrolysis was found to be a 3:1 N₄Co^III to PPi complex. Factors affecting the formation and degradation of this reactive species are discussed.     

Reactivity of hydroxoaquatetraminecobalt(III) towards hydrolysis and condensation of phosphate esters in microemulsion media

Hydroxoaquatetraminecobalt(III)-promoted hydrolysis and condensation reactions of pyrophosphate were investigated at 10–3 m concentration in different microemulsion systems. The reactions were monitored by measurement of orthophosphate (Pi) in quenched reaction aliquots. The reaction mixtures for condensation studies consisted of an equimolar amount of Pi added to the preformed 1:1 phosphate complex [Co(Pi)(en)2], (en=ethylenediamine). Similarly, for the hydrolytic studies, an equimolar amount of [Co(tn)2]3+ was added to the preformed 1:1 pyrophosphate complex [Co(PPi)(tn)2], (tn=trimethylenediamine; PPi=pyrophosphate). The results indicate an increased reactivity for hydrolysis and condensation reactions for oil in water microemulsion systems under the conditions of the study.     

Resonant ultrasound spectroscopy measurement of Young's modulus,shear modulus and Poisson's ratio as a function of porosity for alumina and hydroxyapatite

Modulus–porosity relationships are critical for engineered bone tissue scaffold materials such as hydroxyapatite (HA), where porosity is essential to biological function. Resonant ultrasound spectroscopy (RUS) measurements revealed that the Young's modulus, E, and shear modulus, G, of both alumina and HA decrease monotonically with increasing volume fraction porosity, P, for 0.06 < P < 0.39 (alumina) and 0.05 < P < 0.51 (HA). Although the elastic moduli of porous materials have been measured by a number of different ultrasonic resonance techniques (of which the RUS technique is one example) and over the last decade the elastic moduli of many solids have been measured by the RUS technique, this study is the first systematic RUS study of porous materials. Comparison of E versus P data for alumina (which has been studied extensively) with literature data from several measurement techniques indicates the RUS technique is effective for modulus–porosity measurements. Another key result is that although the HA specimens included in this study have a unimodal pore size distribution, the details of the decrease in E and G with increasing P agree well with literature data for HA with both unimodal and bimodal pore size distributions. In addition, Poisson's ratio exhibits a local minimum in the porosity range of 0.2 < P < 0.25 for both HA and alumina, which may be related to the pore morphology evolution during sintering.     

Parallel synthesis of a biased library of thiazolidinones as novel sodium channel antagonists

A biased chemical library containing 91 differentially substituted thiazolidinones was prepared in an effort to improve the pharmacology of a known anticonvulsant agent V102862. The collection was prepared in a single step multi-component condensation reaction that produced good yields and very high crude purity (75%-85%). Seven compounds, identified within the library were shown to be more potent than V102862, our parent reference compound, in an electrophysiological assay measuring sodium channel antagonism. The most potent compound, 3-(2-piperidinylethyl)-2-(3-(3-trifluoromethylphenoxy)phenyl)thiazolidinone, has a Ki of 90 nM.     

Determination of the structural formula of sodium tris-carbonatocobaltate(III), Na<Subscript>3</Subscript>[Co(CO<Subscript>3</Subscript>)<Subscript>3</Subscript>]·3H<Subscript>2</Subscript>O by thermogravimetry

The existence of an inner sphere water in sodium tris-carbonatocobaltate(III) prepared by the Bauer and Drinkard method was confirmed by thermogravimetry, which led to its formulation as sodium aquo-tris-carbonatocobaltate(III) dihydrate, Na₃[Co(H₂O)(CO₃)₃]·2H₂O. Hydrolytic study on 4-nitrophenylphosphate promoted by [Co(tn)₃]³⁺ afforded corborating evidence for the existence of inner sphere water in the complex leading to its formulation as [Co(tn)₃(H₂O)]³⁺. Another variety of the tris-carbonato anion, [Co(NH₃)₆][Co(CO₃)₃], was prepared and subjected to thermogravimetric analysis, and the absence of inner sphere water in the compound was confirmed. The plausible existence of inner sphere water for the compounds that emanate from the synthetic routes utilizing the Bauer and Drinkard method in the crystalline phase is proposed.     

Gas Chromatography–Mass Spectrometry Determination of Pregabalin in Human Plasma Using Derivatization Method

A gas chromatography–mass spectrometry method for the determination of pregabalin in human plasma is described. The procedure involves precipitation of protein, liquid–liquid extraction with ethylene glycol monomethyl ether, and derivatization with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide as additive. Separation was attained on HP column (30 m × 0. 25 mm ID, 0.25 μm) coupled with mass spectrometric detector using electron impact selected ion monitoring. The assay showed an excellent linearity in the concentration range of 0.36–10 μg mL^?1 with correlation coefficient (r²) values of 0.999. The intra- and inter-day assay variations for three different concentration levels were less than 10%. The limit of quantification was detected at 0.36 μg mL^?1. The method is highly specific, precise, accurate, and reproducible and could also be applied for the determination of pregabalin in human plasma.     

Monitoring Phosphorylation and Dephosphorylation Reactions by Surface-Enhanced Raman Scattering (SERS) in Model Compounds

Abstract

Raman and Surface-Enhanced Raman Scattering (SERS) spectra of phosphates, polyphosphates, and various phosphate complexes have been recorded. Bands of the vibrational spectra were assigned. The comparison of SERS spectra obtained by using colloidal silver with the corresponding Raman spectrum reveals enhancement and shifts in some bands, suggesting a possible partial charge-transfer mechanism in the SERS effect. Phosphorylation and dephosphorylation reactions brought about by the reactions of cobalt (III) bis trimethylenediamine phosphate/pyrophosphate complexes with nitrophenol/nitrophenyl phosphates are described.     

Fabrication of new solid state phosphate selective electrodes for environmental monitoring

A highly selective and sensitive phosphate sensor has been fabricated by constructing a crystal disk consisting of variable mixtures of aluminium powder (Al), aluminium phosphate (AlPO₄) and powdered copper (Cu). The membrane sensor exhibits linear potential response in the concentration range of 1.0 × 10⁻¹ to 1.0 × 10⁻⁶ mol L⁻¹. The proposed sensor also exhibits a fast response time of <60 s. Its detection limit is lower than 1.0 × 10⁻⁶ mol L⁻¹. The electrode has a long lifetime and can be stored in air when not in use. The selectivity of the sensor with respect to other common ions is excellent.