The characterization for the binding of calcium and terbium to Euplotes octocarinatus centrin

Centrin is a member of the EF-hand superfamily that plays critical role in the centrosome duplication and separation. In the present paper, we characterized properties of metal ions binding to Euplotes octocarinatus centrin (EoCen) by fluorescence spectra and circular dichroism (CD) spectra. Changes of fluorescence spectra and alpha-helix contents of EoCen proved that Tb(3+) and Ca(2+) induced great conformational changes of EoCen resulting in exposing hydrophobic surfaces. At pH 7.4, Ca(2+) (and Tb(3+)) bond with EoCen at the ratio of 4:1. Equilibrium experiment indicated that Ca(2+) and Tb(3+) exhibited different binding capabilities for C- and N-terminal domains of protein. C-terminal domain bond with Ca(2+) or Tb(3+) approximately 100-fold more strongly than N-terminal. Aromatic residue-sensitized Tb(3+) energy transfer suggested that site IV bond to Tb(3+) or Ca(2+) more strongly than site III. Based on fluorescence titration curves, we reckoned the conditional binding constants of EoCen site IV quantitatively to be K(IV)=(1.23+/-0.51)x10(8)M(-1) and K(IV)=(6.82+/-0.33)x10(5)M(-1) with Tb(3+) and Ca(2+), respectively. Metal ions bond to EoCen in the order of IV>III>II, I.     

Metabonomics studies of intact hepatic and renal cortical tissues from diabetic db/db mice using high-resolution magic-angle spinning 1H NMR spectroscopy

A metabonomics approach based on high-resolution magic-angle spinning (HRMAS) ¹H NMR spectroscopy was applied to investigate the metabolite composition in intact hepatic tissues and renal cortical tissues from db/db mice of 8 weeks old, an animal model of type 2 diabetes mellitus. Compared to the control group, the hepatic tissues of diabetic mice have elevated levels of triglyceride and bile acid and declined levels of trimethylamine-N-oxide, phosphocholine, glycerophosphocholine, and choline. The biochemical changes are less obvious in renal cortical tissues of diabetic mice. The WET_CPMG pulse sequence was selected for our metabonomics study after the quality and reproducibility of the spectra obtained from the NOEPR, NOEPR_CPMG, and WET_CPMG pulse sequences were analyzed together with principal component analysis. The influence of line-broadening factor of exponential window function for spectral manipulation on class separation was paid attention to for the first time, and an optimal value was obtained under our experimental conditions. These studies show the efficiency of HRMAS ¹H NMR spectroscopy for tissue metabonomics study in combination with multivariate statistical analysis, which may help to explore the etiological factor of diabetes mellitus from a new perspective.

A new luminol chemiluminescence reaction using a tetravalent nickel-periodate complex as the oxidant

A modified sequential extraction procedure was developed and applied to characterize the species of metals in fly ash. Two fly ash samples were collected from a coal-fired thermal power plant located in the north of China. A sample was collected from the conventional pulverized coal (PC) combustor and another from the circulating fluidized bed (CFB) combustor. After extraction by the proposed sequential extraction procedure, the elements in the fly ash samples were divided into a water-extractable fraction (F1), an acid-soluble fraction (F2), a reducible fraction (F3), an oxidizable fraction (F4) and a residual fraction (F5). Except for Cu, V, Cd in the PC sample and V, Zn in the CFB sample, most of the other metals were present in the residual fraction (F5), which was very difficult to release into the environment. The fraction distribution patterns in the two samples were also compared. The results indicated that the distribution of metals in different fractions in fly ash samples were probably impacted by different combustion processes.     

Synthesis of a novel tripodand having 3-hydroxy-2-naphthoeic amide groups and its anion recognition ability

A novel tripodand having 3-hydroxy-2-naphthoeic amide groups was prepared by the reaction of 1,3,5-tris(aminomethyl)-2,4,6-trimethylbenzene with 3-allyloxy-2-naphthoeic acid chloride followed by thermal Claisen rearrangement. This tripodand can exhibit the anion binding ability in chloroform solution. In particular, it can bind with acetate, dihydrogen phosphate, and fluoride ions to form 1:1 complexes.     

Formation of super-concentrated hydrochloric acid in the third phase in tertiary amine N235-PtCl 6 2− -HCl system and its influences on the Pt microemulsion extraction

In this paper, we have investigated the formation of the third-phase in tertiary amine (N235)-PtCl ₆ ^2? -HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering (SAXS) experiments demonstrate the appearance of nano-aggregates, i.e., water-in-oil reversed micelles, in the third phase. The experimental results indicate that (1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H⁺ to H₂O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid. (2) The occurrence of the super-concentrated HCl results in a great amount of H⁺ and Cl^? ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions. It is possible that H⁺ ions participate in the formation of such complexes as H _m PtCl ₆ ^z+ in the super-concentrated hydrochloric acid. (3) The relative contents of various H _m PtCl ₆ ^z+ complexes are different corresponding to the H⁺ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules (R₃NH⁺) with various H _m PtCl ₆ ^z+ complexes plays an important role in affecting the platinum extraction behaviors.     

LC–ESI–MS Determination of Imperatorin in Rat Plasma After Oral Administration and Total Furocoumarins of Radix Angelica dahuricae and its Application to a Pharmacokinetic Study

A simple, rapid, sensitive and reliable liquid chromatography–electrospray ionization mass spectrometry method for the quantification of imperatorin in rat plasma after oral administration and total furocoumarins of Radix Angelica dahuricae has been established. The plasma samples were deproteinized by adding internal standard (IS) osthole solution, which was prepared by acetonitrile. The analysis was performed on a Shim-pack C₁₈ column (150 × 2.0 mm i.d., 5 μm) using acetonitrile and 0.5% formic acid solution (70:30, v/v) as a mobile phase. The detection was performed on a quadrupole mass spectrometer detector with an ESI interface operated in the selected ion monitoring mode. The linear quantification range of the method was 2–4000 ng mL^?1 in rat plasma with a correlation coefficient greater than 0.99, the limit of detection (LOD) was 0.5 ng mL^?1 and the lower limit of quantification (LLOQ) 2 ng mL^?1. The intra- and inter-day relative standard deviations (RSD) were less than 2.5 and 3.5%, respectively. The recoveries were above 90%. The validated method was successfully applied to a pharmacokinetic study of imperatorin in rats after oral administration and total furocoumarins of Radix Angelica dahuricae.     

A Rapid Method for the Analysis of Ten Compounds in Psoralea corylifolia L. by UPLC

The objective of this study was to develop a simple, efficient and reliable method for routine quantitative analysis for Psoralea corylifolia L. An ultra performance liquid chromatography with DAD detector system was employed for simultaneous quantification of ten compounds. The chromatographic analysis was performed by UPLC with C₁₈ column and gradient elution of 0.05% formic acid aqueous solution and acetonitrile in 16 min. All calibration curves were linear (R ² ≥ 0.9990) over the tested ranges. The LOD and LOQ were lower to 13.07 and 39.22 ng mL^?1 with 2 μL of injection volume, respectively. The intra- and inter-day precisions as determined from sample solutions were below 4.1 and 4.2%. The average recoveries were ranged from 94.2 to 108.8% with RSDs ≤ 4.6%. This validated method was applied for the analysis of ten analytes in P. corylifolia L. from different origins. The variation of the content of ten compounds was remarkable among the tested samples: psoralenoside increased from 7.42 to 17.04 mg g^?1, isopsoralenoside from 6.05 to 14.34 mg g^?1, psoralen from 2.37 to 3.90 mg g^?1, isopsoralen from 2.53 to 3.65 mg g^?1, neobavaisoflavone from 1.59 to 2.96 mg g^?1, bavachin from 1.02 to 2.35 mg g^?1, psoralidin from 0.45 to 1.91 mg g^?1, isobavachalcone from 1.33 to 4.71 mg g^?1, corylifol A from 1.02 to 2.40 mg g^?1 and bakuchiol from 28.10 to 63.89 mg g^?1.     

A Simple and Rapid CZE Determination of Tiapride Hydrochloride and Related Impurities in Pharmaceutical Formulations

A simple, fast, inexpensive capillary zone electrophoresis method for the separation and determination of tiapride hydrochloride and its two related impurities in pharmaceutical formulations has been developed and validated. The successful separation of these compounds was achieved in less than 3 min using a fused silica capillary and photodiode array detector at 218 nm. The best conditions were obtained using a 10 mM sodium tetraborate (pH 8.0) as the running buffer. The linear responses covered the ranges from 1.0 to 100 μg mL^?1 (R = 0.9989) for tiapride hydrochloride. The detection (LOD) and quantitation limits (LOQ) for tiapride hydrochloride were 2.7 and 9.0 μg mL^?1, respectively. The intra- and inter-day relative standard deviations for migration times and peak areas were less than 0.47 and 5.7%, respectively. The method was validated for the determination of tiapride hydrochloride in commercial tablets.     

LC Separation and Quantification of Tocopheryl Polyethylene Glycol Succinate and Tocopheryl Acid Succinate in TPGS Reaction Mixture

An analytical method was proposed for the determination of d-α-tocopheryl polyethylene glycol 1,000 succinate (TPGS 1000) and d-α-tocopheryl acid succinate (TAS) in TPGS reaction mixture with a simple and inexpensive reversed-phase liquid chromatographic method. The LC separation was carried out on a C18 analytical column with UV detection at 284 nm using acetonitrile and water (90:10, v/v) with 0.5% acetic acid (pH 3.73) at a flow rate of 1.5 mL min^?1. The average recoveries of TPGS were between 95.41 and 96.82%, while those of TAS were between 96.69 and 102.39%. Within-day and day-to-day relative standard deviations of TPGS were less than 0.23 and 0.29%, while those of TAS were less than 0.17 and 0.27%. The content of TPGS was determined in terms of the hydrolyzed α-tocopherol. The alkaline hydrolysis process demonstrated high α-tocopherol recoveries between 98.78 and 103.05%. This method has been applied successfully to the accurate determination of TAS and TPGS in highly complex reaction mixture to monitor the reaction process progress.     

RP-LC Quantification and Pharmacokinetic Study of Iriflophenone 2-O-α-Rhamnopyranoside in Rat Plasma

Iriflophenone 2-O-α-rhamnopyranoside (IP2R) is one of the main bioactive constituents of the leaves of Aquilaria sinensis (Lour.) Gilg, used in traditional Chinese medicines. A simple, rapid, and sensitive reversed-phase high-performance liquid chromatographic method has been developed for analysis of IP2R in rat plasma after intravenous administration. The analyte was extracted from plasma samples with methanol as deproteinization agent. Analysis was performed on an 250 mm × 4.6 mm i.d., 5-μm particle, C₁₈ column with a 8 mm × 4.6 mm i.d., 5-μm particle, RP-18 guard column; the mobile phase was acetonitrile–H₂O–acetic acid 22:78:0.01 (v/v) at a flow-rate of 1.0 mL min^?1. UV detection was at 289 nm. The calibration plot was linear in the range 0.01–33.33 μg mL^?1 (r = 0.9997, n = 5) in rat plasma. The lower limits of detection and quantification were 0.004 and 0.01 μg mL^?1. Intra-day and inter-day precision were 1.18–3.96 and 1.29–2.81%, respectively. Average extraction recovery from plasma was more than 95%. This assay method was successfully used to study the pharmacokinetics of IP2R in rats after a single dose of 25 mg kg^?1 by intravenous administration; the plasma concentration–time curve of IP2R conformed to a two-compartment open model.