Reference Electrode for Ionic Liquids

Reference electrodes for room temperature ionic liquid (RTIL) applications were constructed that have a known and reproducible potential versus the ferrocene/ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag⁺ couple type, or of the second kind, based on Ag/AgCl in M⁺Cl^?. The former uses AgNO₃ salt and the latter tetrabutylammonium chloride, Bu₄NCl, dissolved in acetonitrile which are then introduced to the ionic liquid of choice for a final concentration of 0.1 M. The reference electrodes can be easily and reproducibly constructed. An ionic contact of these reference systems with the test electrolyte was made using an asbestos fiber liquid junction. The internal compartment of the reference system was filled with the same ionic liquid as used for the electrochemical experiment. The performance of these reference electrodes was tested in selected ionic liquids using the ferrocene/ferrocenium redox couple. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized in the following ionic liquids: 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF₄), 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI(CF₃SO₂)₂N), and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIPF₆). It has been found that the formal potentials of the examined reference systems are stable over several days. There is a linear relationship for the temperature studied in the range from 25 to 60 °C.     

An optimized protocol for nano-LC-MALDI-TOF-MS coupling for the analysis of proteolytic digests of glycoproteins

Matrix-assissted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analyses of complete proteolytic digests are often hampered by contaminations and the complexity of the sample. This results in suppression effects and the formation of adducts which are difficult to assign, thus leading to low scores in database searches. In particular, signals of post-translationally modified peptides such as glycopeptides are often of low intensity or completely suppressed. Online liquid chromatography electrospray ionization mass spectrometry (ESI-MS) can, in part, overcome this problem, but the analytes are completely consumed during the run. Coupling of nano-flow HPLC (nano-LC), microfractionation and MALDI-TOF-MS combines separation and high-sensitivity UV detection with the possibility of collecting fractionated peptides and preserving the sample for detailed mass spectrometric analyses. Here we report on an optimized protocol for nano-LC-MALDI-TOF-MS analyses of glycoproteins. This protocol improves spectral quality, resulting in better protein identification scores in database searches. Furthermore, post-translationally modified peptides could be detected with higher sensitivity by changing the experimental conditions, allowing assignment, localization and characterization of the respective carbohydrate substituents.     

Identification and screening of chemical constituents with hepatoprotective effects from three traditional Chinese medicines for treating jaundice

The constituents with hepatoprotective activity were investigated in three traditional Chinese medicine formulae for treating jaundice, namely, Zhi‐Zi‐Da‐Huang‐Tang, Yin‐Chen‐Hao‐Tang, and Da‐Huang‐Xiao‐Shi‐Tang. By using liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry and liquid chromatography coupled with ion trap mass spectrometry, 79 chemical constituents were identified unambiguously or tentatively in three formulae based on the accurate molecular weight, mass spectrometric fragmentation behavior, and comparison with reference standards. Then the hepatoprotective activities of 27 constituents were evaluated on tert‐butylhydroperoxide‐injured BRL‐3A cells. The results indicated that 11 constituents, including protocatechic acid ( 19 ), epijasminoside A ( 56 ), rutin ( 71 ), tetrahydropalmatine ( 76 ), rhaponticin ( 80 ), 3,4‐dicaffeoylquinic acid ( 82 ), 3,5‐dicaffeoylquinic acid ( 85 ), diosmetin‐7‐O‐glucoside ( 90 ), jatrorrhizine ( 93 ), berberine ( 100 ), and daidzein ( 101 ) exerted hepatoprotective activities. Interestingly, most of the crude drugs in three formulae contained hepatoprotective active constituents, and the combinations of constituents from different crude drugs exhibited greater effects. This result provided evidence to the traditional Chinese medicine theory of combining several drugs together to exert synergistic efficacy.     

Covalent versus Electrostatic Strategies for Nanoparticle Immobilisation

We demonstrate that in neutral electrolytes, a polyelectrolyte‐based (ω‐mercaptoacid/poly‐L ‐lysine) immobilisation strategy for as‐prepared electrostatically stabilised metal nanoparticles is a powerful alternative to often difficult to control dithiol approaches. Our data confirm straightforward preparation of high‐coverage nanoparticle electrodes with fast kinetics and an electrochemical window of up to 1.5 V even in unbuffered solutions, under both stationary and hydrodynamic conditions. The stability region is limited by reductive desorption of the mercaptocarboxylic acid at negative potentials, and by nanoparticle oxidation at positive potentials. The electrostatic immobilisation is valuable for the study of electroanalytical and electrocatalytic processes using nanoparticulate electrode materials.     

Efficient DMTMM Promoted Nucleoside Loading of CPG Solid Support for Oligonucleotide Synthesis

Abstract

A simple and efficient process for the attachment of protected 2′‐deoxynucleosides to the solid support controlled pore glass (CPG) via succinyl linkage using the mild, non‐carbodiimide dehydrating agent 4‐(4,6‐dimethoxy‐1,3,5‐triazin‐2‐yl)‐4‐methylmorpholinium chloride (DMTMM) has been developed. The protocol is cost effective, does not require anhydrous conditions and is easy to implement.     

Isophorone－based Fluorescent Dopant for Red Organic Electrolumi－nescence Device

lsophorone-based red fluorescent compound 3-(dicyanomethy-lene ) -5, 5-dimethyi- 1- [ 2- ( N-ethyl-3-carbazyi ) ethylene ] cyciohe-xene (DCDCC) was synthesized for use in organic Hght-emit-ring diodes (OLEDs). DCDCC was characterized by narrow emission in photoluminescence with full.width at half-maximum of only 50 nm in solution and in thin solid film of 70 nm width. devices with configuration of ITO/NPB/Alq3:DCDCC/Alq3/Mg: Ag were fabricated utilizing DCDCC as dopant emitter. An efficient red emission peaked at 612 nm was obtained for the device with 1% (wt.%) DCDCC in Alq3. The maximum luminance and current efficiency were as high as 3700 cd/m^2 at 14 V and 1.25 cd/A at 150 mA/cm^2, respective-ly.     

Preparation and application of novel zwitterionic monolithic column for hydrophilic interaction chromatography

A novel zwitterionic hydrophilic porous monolithic stationary phase was prepared based on the thermal‐initiated copolymerization of N,N‐dimethyl‐N‐(3‐methacryl‐amidopropyl)‐N‐(3‐(sulfopropyl)ammonium betaine and ethylene glycol dimethacrylate. A typical hydrophilic separation mechanism was observed at a highly organic mobile phase (ACN >60%) on this optimized zwitterionic hydrophilic interaction chromatography (HILIC) monolithic stationary phase. Good permeability, stability, and column efficiency were observed on the final monolithic column. Additionally, a weak electrostatic interaction for charged analytes was confirmed in analysis of six benzoic acids by studying the influence of mobile phase pH and salt concentration on their retention behaviors on the obtained zwitterionic HILIC monolithic column. The optimized zwitterionic HILIC monolith exhibited good selectivity for a range of polar test analytes.     

Novel Reaction for Rapid,Simple, and Sensitive Determination of Molybdenum in Various Samples

Abstract

A new sensitive, selective, rapid, and reproducible method is presented for the analysis of trace amounts of molybdenum (VI) (Mo(VI)). The method is based on the reaction of molybdenum (VI) with a new analytical reagent, 6‐(5‐Chloro‐2‐hydroxy‐4‐sulfophenylazo)‐5‐hydroxy‐1‐naphthalenesulfonic acid, disodium salt. Under optimum reaction conditions, molybdenum (VI) forms a red complex with a maximum absorption peak at 589 nm. The color reaction is rapidly completed at room temperature. The apparent molar absorption coefficient and Sandell sensitivity were 1.13×10⁴ L · mol^?1 · cm^?1 and 0.0084 µg · cm^?2, respectively. Beer's law was obeyed up to 8.5 µg · mL^?1. Methods for the determination of Mo(VI) by first‐derivative spectrophtometry have also been proposed at 547 and 625 nm. The proposed methods offer the advantages of sensitivity, rapidity, selectivity, and simplicity without any prior separation or extraction. The methods have been applied to the determination of Mo(VI) in various environmental samples and some alloys; satisfactory results have been obtained.     

A CE‐LIF method based on long wavelength fluorescence labeling for the analysis of thiols in human urine

A rapid and robust CE method using a long wavelength fluorescent reagent 1,7‐dimethyl‐3,5‐distyryl‐8‐phenyl‐(2‐maleimide)difluoroboradiaza‐s‐indacene as the labeling reagent has been developed for the simultaneous determination of thiols, including glutathione, cysteine, homocysteine, N‐acetylcysteine, cysteinylglycine, and penicillamine. The derivatization reaction was carried out in 14 mmol/L pH 8.5 borate buffer at 30°C for 6 min and the labeled thiols derivatives were separated with the running buffer containing 30 mmol/L pH 7.4 phosphate, 30% v/v acetonitrile and 8 mmol/L SDS within 12 min. Detection limits ranged from 0.4 to 2.4 nmol/L. To demonstrate the capability of this method, it was applied to the analysis of thiols in human urine with recoveries of 92.4–105.6%. The derivatization reaction was much faster at milder conditions, and the analysis was rapider. Moreover, with excitation wavelength at long wavelength region, background interference from samples was reduced effectively. The present method seems to be a potential choice for quantifying thiols in human urine.     

Molecular mechanics parameters for the FapydG DNA lesion

FapydG is a common oxidative DNA lesion involving opening of the imidazole ring. It shares the same precursor as 8-oxodG and can be excised by the same enzymes as 8-oxodG. However, the loss of the aromatic imidazole in FapydG results in a reduction of the double bond character between C5 and N7, with an accompanying increase in conformational flexibility. Experimental characterization of FapydG is hampered by high reactivity, and thus it is desirable to investigate structural details through computer simulation. We show that the existing Amber force field parameters for FapydG do not reproduce X-ray structural data. We employed quantum mechanics energy profile calculations to derive new molecular mechanics parameters for the rotation of the dihedral angles in the eximidazole moiety. Using these parameters, all-atom simulations in explicit water reproduce the nonplanar conformation of cFapydG in the crystal structure of the complex with L. lactis glycosylase Fpg. We note that the nonplanar structure is stabilized by an acidic residue that is not present in most Fpg sequences. Simulations of the E-->S mutant, as present in E. coli, resulted in a more planar conformation, suggesting that the highly nonplanar form observed in the crystal structure may not have direct biological relevance for FapydG.     

Auxiliary basis sets for density‐fitting second‐order Møller–Plesset perturbation theory: Weighted core‐valence correlation consistent basis sets for the 4d elements Y–Pd

Auxiliary basis sets (ABS) specifically matched to the cc‐pwCVnZ‐PP and aug‐cc‐pwCVnZ‐PP orbital basis sets (OBS) have been developed and optimized for the 4d elements Y‐Pd at the second‐order Møller‐Plesset perturbation theory level. Calculation of the core‐valence electron correlation energies for small to medium sized transition metal complexes demonstrates that the error due to the use of these new sets in density fitting is three to four orders of magnitude smaller than that due to the OBS incompleteness, and hence is considered negligible. Utilizing the ABSs in the resolution‐of‐the‐identity component of explicitly correlated calculations is also investigated, where it is shown that i‐type functions are important to produce well‐controlled errors in both integrals and correlation energy. Benchmarking at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations level indicates impressive convergence with respect to basis set size for the spectroscopic constants of 4d monofluorides; explicitly correlated double‐ζ calculations produce results close to conventional quadruple‐ζ, and triple‐ζ is within chemical accuracy of the complete basis set limit. © 2013 Wiley Periodicals, Inc.     

A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteins

A new, versatile, multiphasic buffer system for high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins in the relative molecular weight range of 300 000-3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above M(r) range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pK(a), as the buffering counterion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6-200 kDa M(r) range, with minimal difficulties in the post electrophoretic identification processes.     

Method development and validation for the analysis of a new anti-cancer infusion solution via HPLC

A fast and simple HPLC method has been developed and validated for the quantification of a completely new anti-cancer drug during the manufacturing process. The combination of four compounds including α-ketoglutaric acid, hydroxymethylfurfural, N-acetyl-L-methionine and N-acetyl-L-selenomethionine, administered intravenously, is still in test phase but has already shown promising results in cancer therapy. HPLC separation was achieved on an RP-18 column with a gradient system. However, the highly different concentrations of the compounds required a variation in the detection wavelength within one run. In order to produce a chromatogram where peaks were comparable on a similar range scale, detection at absorption maxima for the two most concentrated components was avoided. After optimization of the gradient program it was possible to detect all four substances within 14 min in spite of their strongly different chemical structure. The method developed was validated for accuracy, repeatability, reproducibility and robustness in relation to temperature and pH of buffer. Linearity as well as the limit of detection and quantification were determined. This HPLC method was found to be precise, accurate and reproducible and can be easily used for in-line process control during the manufacture of the anti-tumour infusion solution.     

Novel Synthetic Method for Muscone

Muscone is a precious fragrant compound scarce in nature. Many attempts to synthesize this unique natural product have been carried out. In this work, a novel synthetic method for the preparation of muscone from 3‐methyl‐15‐hydroxypentadecanoate is provided. Benzimidazolium salt was used as tetrahydrofolate coenzyme model at formic acid oxidation level and Grignard reagent as nucleophile to which a one‐carbon unit was transferred. The biomimetic synthesis of muscone was successfully accomplished using the addition‐hydrolysis reaction of benzimidazolium salt with the Grignard reagent.     

Active ruthenium‐(N‐heterocyclic carbene) complexes for hydrogenation of ketones

Four ruthenium‐N‐heterocyclic carbene complexes ( 3–6 ) have been prepared and the new compounds characterized by C, H, N analyses, ¹H‐NMR and ¹³C‐NMR. The reduction of ketones to alcohols via transfer hydrogenation was achieved with catalytic amounts of complexes 3–6 in the presence of t‐BuOK. Copyright © 2006 John Wiley & Sons, Ltd.     

Separation and quantitation of fructose-6-phosphate and fructose-1 ,6-diphosphate by LC-ESI-MS for the evaluation of fructose-1,6-biphosphatase activity

An LC-ESI-MS method was developed for the identification and quantification of fructose-1,6-biphosphate (F1,6BP) and fructose-6-phosphate (F6P), respectively the substrate and the product of the enzymatic reaction catalysed by fructose-1,6-bisphosphatase (F1,6BPase). F1,6BPase, expressed predominantly in liver and kidney, is one of the rate-limiting enzymes of hepatic gluconeogenesis and has become a target for the development of new drugs for type 2 diabetes. The two sugar phosphates were separated on a Phenomenex Luna NH2 column (150 mm x 2.0 mm id) using the following mobile phase: 5 mM triethylamine acetate buffer/ACN (80:20) v/v in a linear pH gradient (from pH = 9 to 10 in 15 min) at the flow rate of 0.3 mL/min. The detection was performed with an IT mass spectrometer in negative polarity (full scan 100-450 m/z) and in SIM mode on the generated anions at m/z = 339 (F1,6BP) and m/z = 259 (F6P). Under the optimised final conditions, the method was validated for accuracy, specificity, precision (inter- and intradays RSD comprised between 1.0 and 6.3% over the range of concentrations used), linearity (50-400 microM), LODs (0.44 microM) and LOQs (1.47 microM), and the method was applied to F6P determination in the F1,6BPase catalysed hydrolysis of F1,6BP.     

Propane Phosphonic Acid Anhydride: A Mild Reagent for β-Lactam Synthesis

The use of propane phosphonic acid anhydride (T3P) as an acid activating reagent was demonstrated in the syntheses of cis β-lactams from the reactions of a glycine Dane salt and various imines.     

Syntheses of L‐Glutamic Acid Analogues for Neuroexcitatory Activity Studies

Starting from D–serine, (2S,3S)‐, (2S,3R)‐substituted‐L‐glutamic acids were prepared via Claisen rearrangement methodology. A variety of the substituents can be introduced at the C‐3 of the L‐glutamic acid backbone.