Quantitative determination of glutathione in single human erythrocytes by capillary zone electrophoresis with electrochemical detection

Glutathione (GSH) in single human erythrocytes is determined by capillary zone electrophoresis with end-column amperometric detection at a gold/mercury amalgam microelectrode. A capillary of 10 microm inner diameter is suitable for determination of GSH in an individual erythrocyte with a good signal-to-noise ratio. The limit of detection is 1 x 10(-7) mol/L or 26 amol and the linear dynamic range is 2 x 10(-7) to 2 X 10(-5) mol/L for the capillary. In this method, the calibration line is obtained with a capillary adsorbed before a certain amount of hemoglobin can be used for the quantification of GSH in the external standardization. The whole cell injection and the lack of necessity of a derivatization reaction lead to more accurate and precise results, which are closer to the macroscopic values of glutathione in human red blood cell (i.e., hemolysate) than those determined by indirect laser-induced fluorescence detection.     

Synthesis of Enantiomerically Pure Carbohydrate-Derived Annulated Cyclopentadienes and Ferrocenes

The cyclopentadienes 3a/b/c, 8b/c, 12a/b/d , and 16a/b/d were prepared as mixtures of regioisomers from the D -mannitol-derivatives 1,6,10 , and 14 and transformed into the ferrocenes 17, 18 , and 19 (73%; 38:17:45), 23, 24 , and 25 (70%; 6:42 :52), 26 (31%), and 27 (27%), respectively. Deprotection of 17–19 with HCl/MeOH gave the H₂O-soluble ferrocenes 20–22 ; chloromercuration and iodination of 17 via 29 led to the C₂-symmetric diiodo-ferrocene 30 . The mono(chloromercurio) derivative 28 , obtained as a by-product, was also transformed into 29 . The structure of the ferrocenes 18 and 19 , and of the bis(chloromercurio)ferrocene 29 has been established by X-ray analysis. The starting cyclopentadienes 3 were obtained in 50% yield from 1 by dialkylation of CpNa, followed by thermolysis of the spiro-annulated 2 . Similarly, dimesylate 6 (from 4 ) gave the spiro-annulated diene 7 and the annulated dienes 8 in about equal amounts; thermolysis transformed 7 into 8 (62%). The dienes 12 were prepared in 15% yield from the ditriflate 10 via 11 , the dimesylate 9 proving insufficiently reactive, and the dienes 16 (49%) from 14 via 15 .     

Direct injection of plasma to determine pseudoephedrine by high performance liquid chromatography with column switching

An HPLC method has been developed for the determination of pseudoephedrine in plasma using column switching. Preparation of the sample was simple in that only 1000 microL of water was added to 200 microL of plasma before injection. A 900 microL aliquot was injected onto the precolumn. Double distilled water was used to elute and remove proteins and polar components in the sample. The components retained on the precolumn were flushed forward onto the analytical column by the mobile phase (acetonitrile-0.2 mol/L ammonium sulphate, 10:90 v/v) with automated column switching. The limit of determination of pseudoephedrine in plasma was 12 ng/mL. The relative standard deviations of intra- and inter-assay for the determination of pseudoephedrine in plasma were 1.2-9.8% over the concentration range 1020-21.8 ng/mL. The mean recovery by on-line solid phase extraction was 94.76% (RSD = 1.1%).     

Kinetic theory of reacting systems

In this paper transport processes of reacting systems are investigated, based on the Boltzmann equations. The Boltzmann equations are solved by means of Grad's moment method to thirteen moments and some formal results are obtained for transport properties. It is shown that the rate coefficients are quadratic functions of hydrodynamic fluxes and are in the form

where

are the scalar moments associated with the reaction and q, J, Π are heat flux, material flux and traceless symmetric stress tensor. k⁽⁰⁾_i is the usual local equilibrium formula for reaction rate constant. Iterative solutions for the equations of change for

, q, J and Π are obtained from which transport coefficients are calculated for the reacting system. It is shown that the solutions, when specialized to nonreacting mixtures, lead to results for the transport coefficients which are exactly in agreement with the Chapman-Enskog theory results. The modifications of the transport coefficients due to reactions are obtained from the iterative solutions and the bracket integrals necessary for their calculations are explicitly given in an appendix.     

Study on osmotic pressures for aqueous lysozyme and alpha-chymotrypsin-electrolyte solutions with two Yukawa potentials

The equation of state (EOS) of Duh and Mier-y-Terán for one Yukawa potential is expanded to two Yukawa potentials to describe the nonidealities of the charged lysozyme and alpha-chymotrypsin solutions. Instead of the classical DLVO theory, the attractive dispersion and double-layer repulsion interactions are represented by two Yukawa potentials, respectively. For the aqueous lysozyme solutions, the only adjustable dispersion energy parameter epsilon/k is regressed and the average deviation is 1.76%. For the aqueous alpha-chymotrypsin solutions, two adjustable parameters (the molecular weight and dispersion energy parameter) are regressed and the average deviation is 7.62%. Some correlation and prediction results are discussed.     

Single-isomer sulfated alpha-cyclodextrins for capillary electrophoresis. Part 2. Hexakis(6-O-sulfo)-alpha-cyclodextrin: synthesis, analytical characterization, and initial screening tests

The second member of the family of single-isomer sulfated alpha-cyclodextrins, the sodium salt of hexakis(6-O-sulfo)-alpha-cyclodextrin (HxS), has been synthesized, analytically characterized, and used as the resolving agent for the capillary electrophoretic separation of the enantiomers of nonionic, weak-acid and weak-base analytes present in our initial screening kit. HxS interacted less strongly with many of the analytes tested than the larger-ring analogs, heptakis(6-O-sulfo)-beta-cyclodextrin (HS) and octakis(6-O-sulfo)-gamma-cyclodextrin (OS). For some of the analytes, the separation selectivities obtained with HxS were complementary to those observed with hexakis(2,3-di-O-acetyl-6-O-sulfo)-alpha-cyclodextrin (HxDAS), HS, and OS. For all analytes, the effective mobilities and separation selectivities as a function of the background electrolyte concentration of HxS followed the trends that were found for HxDAS, HS, and OS.     

Experimental verification of a predicted, previously unseen separation selectivity pattern in the capillary electrophoretic separation of noncharged enantiomers by octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin

The capillary electrophoretic separation of noncharged enantiomers with single-isomer anionic resolving agents is reexamined here with the help of the charged resolving agent migration model. Two general model parameters have been identified that influence the effective mobility, separation selectivity and mobility difference curves of the enantiomers: parameter b, called binding selectivity (K(RCD)/K(SCD)), and parameter s, called size selectivity (mu(o)RCD/mu(o)SCD). Analysis of the model in terms of these parameters indicates that in addition to the known, previously observed separation selectivity vs. resolving agent concentration patterns, a new pattern, increasing separation selectivity with increasing resolving agent concentration, is also possible provided that (i) K(RCD)/K(SCD)<1 and mu(o)RCD/mu(o)SCD>1 and (K(RCD)mu(o)RCD)/(K(SCD)mu(o)SCD)>1, or (ii) K(RCD)/ K(SCD)>1 and mu(o)SCD/mu(o)SCD<1 and (K(RCD)mu(o)RCD)/(K(SCD)mu(o)SCD)<1. This hitherto unseen separation selectivity pattern was experimentally verified during the capillary electrophoretic separation of the enantiomers of O-isopropyl p-nitrophenyl methylphosphonate with the single-isomer octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin as resolving agent.     

Rational design of an “all-in-one” phototheranostic

We report here porphodilactol derivatives and their corresponding metal complexes. These systems show promise as “all-in-one” phototheranostics and are predicated on a design strategy that involves controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation. The requisite balance was achieved by tuning the aromaticity of these porphyrinoid derivatives and forming complexes with one of two lanthanide cations, namely Gd³⁺ and Lu³⁺. The net result led to a metalloporphodilactol system, Gd-trans-2, with seemingly optimal ISC efficiency, photothermal conversion efficiency and fluorescence properties, as well as good chemical stability. Encapsulation of Gd-trans-2 within mesoporous silica nanoparticles (MSN) allowed its evaluation for tumour diagnosis and therapy. It was found to be effective as an “all-in-one” phototheranostic that allowed for NIR fluorescence/photoacoustic dual-modal imaging while providing an excellent combined PTT/PDT therapeutic efficacy in vitro and in vivo in 4T1-tumour-bearing mice.

We report here porphodilactol derivatives and their corresponding metal complexes as “all-in-one” phototheranostics by controlling the relationship between intersystem crossing (ISC) and photothermal conversion efficiency following photoexcitation.     

Application of Functionalized Ag Nanoparticles for the Determination of Proteins at Nanogram Levels Using the Resonance Light Scattering Method

A novel method for the determination of proteins in aqueous solutions has been developed based on the enhancement of resonance light scattering (RLS) of Ag nanoparticles in the presence of proteins. Factors including acidity of the media, concentration of Ag hydrosol, reaction time, temperature, and interference of non-protein substances were investigated. Under the optimal conditions, with the enhanced RLS signals at 452nm, the linear ranges of calibration curves were 0–0.8µgmL^–1 for bovine serum albumin (BSA), 0–1.2µgmL^–1 for human serum albumin (HSA), and 0–2.5µgmL^–1 for human -IgG (-IgG), respectively. The detection limits were 1.3ngmL^–1 for BSA, 10ngmL^–1 for HAS, and 5.7ngmL^–1 for -IgG.This method has been applied to the analysis of synthetic samples and real human serum samples, and the results were in good agreement with those reported by the hospital, indicating that the method presented here is not only sensitive and simple, but also reliable and suitable for practical applications.     

Synthesis and Characteristics of a New Fluorogenic Substrate for Horseradish Peroxidase

N,N′-Dicyanomethyl-o-phenylenediamine was synthesized with a 90% yield by a reaction ofo-phenylenediamine with chloroacetonitrile in triethylamine. Our experimental results showed that it was the effective fluorogenic substrate for horseradish peroxidase (HRP) and hemin. TheK_mfor the HRP system was 48 μM,and that for hemin was 1.3 μM.Properties of the substrate were evaluated from the detection limits of enzymes and H₂O₂. The linear ranges for the determination of HRP and hemin were 21–150 pMand 2–20 nM,respectively. The linear range for the determination of H₂O₂using HRP or hemin was 18–140 and 60–1000 nM,respectively. The structural elucidation of the fluorescent product using NMR and mass spectral techniques was proposed to be 1,2-dihydro-2-imido-imidazo[1,2-a] quinoxaline. Based on the product structure and earlier reports, the possible reaction mechanism of HRP and the substrate was also proposed, i.e., two steps for ring closures, one step of isomerization, and a final step of oxidative dehydrogenation.