CE‐ESI‐MS coupled with dynamic pH junction online concentration for analysis of peptides in human urine samples

In this article, an approach has been developed for the analysis of some small peptides with similar pI values by CE‐ESI‐MS based on the online concentration strategy of dynamic pH junction. The factors affected on the separation, detection and online enrichment, such as BGE, injection pressure, sheath flow liquid and separation voltage have been investigated in detail. Under the optimum conditions, i.e. using 0.5 mol/L formic acid (pH 2.15) as the BGE, preparing the sample in 50 mM ammonium acetate solution (pH 7.5), 50 mbar of injection pressure for 300 s, using 7.5 mM of acetic acid in methanol–water (80% v/v) solution as the sheath flow liquid and 20 kV as the separation voltage, four peptides with similar pI values, such as L ‐Ala‐L ‐Ala (pI=5.57), L ‐Leu‐D ‐Leu (pI=5.52), Gly‐D ‐Phe (pI=5.52) and Gly‐Gly‐L ‐Leu (pI=5.52) achieved baseline separation within 18.3 min with detection limits in the range of 0.2–2.0 nmol/L. RSDs of peak migration time and peak area were in the range of 1.45–3.57 and 4.93–6.32%, respectively. This method has been applied to the analysis of the four peptides in the spiked urine sample with satisfactory results.     

Improved analyte detectability of proteins and peptide lysates by means of multiple large‐volume injection in LC‐MS

A ‘multiple (trapping) large‐volume injection’ approach was developed for the analysis of peptides and proteins. In this way, a maximally 10‐fold gain in sensitivity could be achieved. The system involves the use of an automated 10‐port switching valve in combination with a 1 mm i.d. trapping/guard column and a 1 mm i.d.×150 mm analytical column. The optimized multiple injection/loading procedure allows quantitative measurements of peptides and protein lysates. Linear calibration curves (R² ? 0.988) over a minimum of two orders of magnitude were generated for a range of peptide and protein standards with sensitivities equal to or even exceeding, those generally achieved only through increasing miniaturization (quantification limit ?0.5 pmol/mL).     

The development and validation of a high‐throughput LC–MS/MS method for the analysis of endogenous β‐hydroxy‐β‐methylbutyrate in human plasma

A high‐throughput, sensitive, and rugged liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the rapid quantitation of β ‐hydroxy‐β ‐methylbutyrate (HMB) in human plasma has been developed and validated for routine use. The method uses 100 μL of plasma sample and employs protein precipitation with 0.1% formic acid in methanol for the extraction of HMB from plasma. Sample extracts were analyzed using LC–MS/MS technique under negative mode electrospray ionization conditions. A ¹³C–labeled stable isotope internal standard was used to achieve accurate quantitation. Multiday validation was conducted for precision, accuracy, linearity, selectivity, matrix effect, dilution integrity (2×), extraction recovery, freeze–thaw sample stability (three cycles), benchtop sample stability (6 h and 50 min), autosampler stability (27 h) and frozen storage sample stability (146 days). Linearity was demonstrated between 10 and 500 ng/mL. Inter‐day accuracies and coefficients of variation (CV) were 91.2–98.1 and 3.7–7.8%, respectively. The validated method was proven to be rugged for routine use to quantify endogenous levels of HMB in human plasma obtained from healthy volunteers.     

Detection and Sequence Identification of Dinucleotides Produced from N‐Phosphoryl Alanine and Four Nucleosides by HPLC‐ESI‐MS/MS

本文利用液相色谱质谱联用技术研究了N－磷酰化丙氨酸和四种核苷（腺苷,尿苷,胞苷和鸟苷）的模板反应产物。结果表明生成了不同类型的单核苷酸和二核苷酸,并且生成的二核苷酸序列也得到了确证。研究结果揭示,二核苷酸骨架裂解形成的c离子可以作为确证二核苷酸序列的诊断离子。本文首次证明不论是在正离子模式还是在负离子模式下,c离子都可以用来确定此反应体系中生成的二核苷酸产物的序列。     

Novel family of triphenylamine‐containing,hole‐transporting,amorphous, aromatic polyamides with stable electrochromic properties

We report the preparation and characterization of a series of novel electrochromic, aromatic poly(amine amide)s with pendent triphenylamine units. The synthesis proceeded via direct phosphorylation polycondensation between a novel diamine, N,N‐bis(4‐aminophenyl)‐N′,N′‐diphenyl‐1,4‐phenylenediamine, and various aromatic dicarboxylic acids. All the poly(amine amide)s were amorphous and readily soluble in many common organic solvents and could be solution‐cast into transparent, tough, and flexible films with good mechanical properties. They exhibited good thermal stability and 10% weight‐loss temperatures above 540 °C. Their glass‐transition temperatures were 263–290 °C. These polymers in N‐methyl‐2‐pyrrolidinone solutions exhibited strong ultraviolet–visible absorption peaks at 307–358 nm and photoluminescence peaks around 532–590 nm in the green region. The hole‐transporting and electrochromic properties were studied with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of poly(amine amide) films prepared by the casting of polymer solutions onto an indium tin oxide coated glass substrate exhibited two reversible oxidation redox couples at 0.65 and 1.03 V versus Ag/AgCl in an acetonitrile solution. All the poly(amine amide)s showed excellent stability with respect to their electrochromic characteristics; the color of the films changed from pale yellow to green and then blue at 0.85 and 1.25 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2085–2098, 2005     

Synthesis and biological activity of novel N‐tert‐butyl‐N,N′‐substitutedbenzoylhydrazines containing 2‐methyl‐3‐(triphenylgermanyl)propoxycarbonyl

In a search for new insect growth regulators with unusual biological properties and different activity spectrum, we thought that the preservation of the bioactive unit and the introduction of 2‐methyl‐3‐(triphenylgermanyl)propoxycarbonyl in N‐tert‐butyl‐N,N′‐dibenzoylhydrazine would enhance their larvicidal activities to a significant degree. Therefore, we designed and synthesized N′‐tert‐butyl‐N′‐[2‐methyl‐3‐(triphenylgermanyl)propoxycarbonyl]‐N‐benzoylhydrazine and analogs by two procedures. These novel compounds were characterized by elemental analyses, IR, and ¹H NMR. At the same time, N‐tert‐butyl‐N‐substitutedbenzoylhydrazines were prepared by a new method, and some reactions involved were studied. The preliminary results indicate that some compounds have inhibitory effects against plant pathogenetic bacteria such as early blight of tomato. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of N,N′,X‐tridentate 2‐iminomethylpyrrole‐coordinated palladium(II) complexes via N─H bond activation of pyrrole moiety

The reaction of [Pd(CH₃CN)₂Cl₂] with N ‐functional group‐substituted 2‐iminomethylpyrrole‐based ligands, namely N ¹‐((1H‐pyrrol‐2‐yl)methylene)‐N ³,N ³‐dimethylpropane‐1,3‐diamine (L_A), N ¹‐((1H‐pyrrol‐2‐yl)methylene)‐N ³‐methyl‐N ³‐phenylpropane‐1,3‐diamine (L_B), N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐(methylthio)propan‐1‐amine (L_C) and N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐methoxypropan‐1‐amine (L_D), resulted in [L_n PdCl] (L_n  = L_A–L_D) complexes in high yield via N─H bond activation of pyrrole moiety without use of base. [L_n PdCl] existed as monomeric four‐coordinated complexes with slightly distorted square planar geometries around the palladium metal center. The ligands show N ,N ′,X ‐tridentate binding mode to the palladium metal center to give two fused ring metallacycles. [L_BPdCl] gave the highest activity (3.29 × 10⁵ g PMMA (mol Pd)⁻¹ h⁻¹) for a methyl methacrylate (MMA) polymerization in the presence of modified methylaluminoxane at 60 °C compared to the other Pd(II) analogues, and resulted in PMMA with higher molecular weight (M _w = 7.16 × 10⁵ g mol⁻¹) and narrower polydispersity index. Syndiotactic‐enriched PMMA resulted in all cases.     

The chiral bioconversion and preclinical pharmacokinetic analysis of (R)‐(+)‐rabeprazole in beagle dogs by HPLC and HPLC‐MS/MS

In order to accurately investigate the preclinical pharmacokinetics of (R)‐(+)‐rabeprazole sodium injection, a reliable high‐performance liquid chromatography (HPLC) method was developed using a Chiral‐AGP column to prove that there is no chiral bioconversion of (R)‐(+)‐rabeprazole to (S)‐(?)‐rabeprazole in beagle dogs after single intravenous administration of (R)‐(+)‐rabeprazole sodium injection. An HPLC–tandem mass spectrometry (HPLC‐MS/MS) method for analysis of (R)‐(+)‐rabeprazole was developed and validated, and used to acquire the pharmacokinetic parameters in beagle dogs. (R)‐(+)‐Rabeprazole and internal standard omeprazole were extracted from plasma samples by protein precipitation and separated on a C₁₈ column using methanol–5 mm ammonium acetate as mobile phase. Detection was performed using a turbo‐spray ionization source and mass spectrometric positive multi‐reaction monitoring mode. The linear relationship was achieved in the range from 2.5 to 5000 ng/mL. The method also afforded satisfactory results in terms of sensitivity, specificity, precision, accuracy and recovery as well as the stability of the analyte under various conditions, and was successfully applied to a preclinical pharmacokinetic study in beagle dogs after single intravenous administrations of (R)‐(+)‐rabeprazole sodium injection at 0.33, 2 and 6 mg/kg. Copyright © 2013 John Wiley & Sons, Ltd.     

N,N,N′,N′,N″‐penta(methyl acrylate)diethylenetriamine: A novel ligand for atom transfer radical polymerization of methyl methacrylate

A novel ligand, N,N,N′,N′,N″‐penta (methyl acrylate) diethylenetriamine (MA₅‐DETA), was synthesized by the reaction of diethylenetriamine with methyl acrylate in almost quantitive yield. The polymerizations of methyl methacrylate with MA₅‐DETA as the ligand and α,α‐dichlorotoluene (DCT) and ethyl 2‐bromoisobutyrate (2‐EBiB) as the initiators, respectively, under different conditions were examined. The polymerization with CuCl/MA₅‐DETA/DCT was closely controlled in bulk and gave polymers with quite narrow molecular weight distributions (M_w/M_n's) of 1.16–1.29. The polymerization with the system CuBr/MA₅‐DETA/EBiB in bulk gave high activity. However, the system was not well controlled and gave the polymers with M_w/M_n = 1.35–1.53. The solution polymerization in anisole with CuBr/MA₅‐DETA/EBiB showed a better‐controlled nature. Moreover, the addition of CuBr₂ into the aforementioned system can further improve its controllability. The M_w/M_n's of the resulting polymers ranged from 1.11 to 1.21. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1963–1969, 2004     

Synthesis and biological activity of novel N‐benzoyl‐N‐tert‐butyl‐N′‐(β‐triphenylgermyl)propionylhydrazines

A series of new N‐benzoyl‐N‐tert‐butyl‐N′‐(β‐triphenylgermyl)propionylhydrazines were synthesized by the condensation reaction of β‐triphenylgermyl propanoic acid with N‐benzoyl‐N‐tert‐butylhydrazines in good yields by using N,N′‐dicyclohexylcorbodiimide as dehydrating agent. These title compounds were evaluated for molting hormone mimicking activity. The results of bioassay showed that the compounds exhibit moderate larvicidal activity, and toxicity assays indicated that the title compounds can induce a premature, abnormal and lethal larval molt. We found that the title compounds possess potential anticancer activities in vitro. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and characterization of a novel organic–inorganic hybrid salt and its application as a highly effectual Brønsted–Lewis acidic catalyst for the production of N,N′‐alkylidene bisamides

In this research, a novel organic–inorganic hybrid salt, namely, N¹,N¹,N²,N²‐tetramethyl‐N¹,N²‐bis(sulfo)ethane‐1,2‐diaminium tetrachloroferrate ([TMBSED][FeCl₄]₂) was prepared and characterized by Fourier‐transform infrared spectroscopy (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), elemental mapping, field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), thermal gravimetric (TG), differential thermal gravimetric (DTG), and vibrating‐sample magnetometry (VSM) analyses. Catalytic activity of the hybrid salt was tested for the synthesis of N,N′‐alkylidene bisamides through the reaction of benzamide (2 eq.) and aromatic aldehydes (1 eq.) under solvent‐free conditions in which the products were obtained in high yields and short reaction times. The catalyst was superior to many of the reported catalysts in terms of two or more of these factors: the reaction medium and temperature, yield, time, and turnover frequency (TOF). [TMBSED][FeCl₄]₂ is a Brønsted–Lewis acidic catalyst; there are two SO₃H groups (as Brønsted acidic sites) and two tetrachloroferrate anions (as Lewis acidic sites) in its structure. Highly effectiveness of the catalyst for the synthesis of N,N′‐alkylidene bisamides can be attributed to synergy of the Brønsted and Lewis acids and also possessing two sites of each acid.     

Novel Ytterbium(III) Selective Membrane Sensor Based on N‐(2‐Pyridyl)‐N′‐(2‐Methoxyphenyl)‐Thiourea as an Excellent Carrier and Its Application to Determination of Fluoride in Mouth Wash Preparation Samples

The construction, performance, and applications of a novel ytterbium(III) sensor based on N‐(2‐pyridyl)‐N′‐(2‐methoxyphenyl)‐thiourea (PMT), as an excellent carrier, in plasticized poly(vinyl chloride) PVC matrix, is described. The influences of membrane composition and pH on the potentiometric response of the sensor were investigated. The sensor exhibits a nice Nernstian response for Yb(III) ion over a wide concentration range of 4 decades of concentration (1.0×10^?6–1.0×10^?2 M), and a detection limit of 5.0×10^?7 M. The response time of the electrodes is between 8 and 10 s, depending on the concentration of ytterbium(III) ions. The proposed sensor can be used for about 8 weeks without any considerable divergence in potential. The sensor revealed very good selectivity for Yb(III) in the presence of several metal ions. The best performance was observed for the membrane containing; 30% PVC, 59% o‐nitrophenyloctyl ether (NPOE) as solvent mediator, 7% PMT, and 4% sodium tetraphenyl borate (NaTPB). It was successfully applied as indicator electrodes in the potentiometric titration of Yb(III) with EDTA and for the determination of fluoride ion in two mouth wash formulations. The proposed La(III) sensor was found to work well under laboratory conditions. It was also used as an indicator electrode in titration of a 1.0×10^?4 M of Yb(III) with a standard EDTA solution (1.0×10^?2 M). It was also used for determination of Yb(III) ion in Xenotime .     

Synthesis of 2‐Aryl‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylates by the Reaction between Hydrazones,Acetylenedicarboxylates, and 1‐Aryl‐N,N′‐bis(arylmethylidene)methanediamines

An efficient approach for the preparation of functionalized 2‐aryl‐2,5‐dihydro‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐1H‐pyrroles is described. The four‐component reaction between aldehydes, NH₂NH₂?H₂O, dialkyl acetylenedicarboxylates, and 1‐aryl‐N,N′‐bis(arylmethylidene)methanediamines proceeds in EtOH under reflux in good‐to‐excellent yields (Scheme 1). The structures of 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS, and, in the case of 4f , by X‐ray crystallography). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Manganese‐based transition metal complexes as new catalysts for olefin polymerizations

Three manganese complexes, Mn(acac)₃ (acac = acetylacetonate), Cp₂Mn (Cp = cyclopentadienyl), and Mn(salen)Cl [salen = 1,2‐cyclohexanediamino‐N,N′‐bis(3,5‐dit‐butyl‐salicylidene)], were used for ethylene and propylene polymerizations. These complexes, in combination with an alkylaluminum cocatalyst such as methylaluminoxane (MAO) or diethyl aluminum chloride (AlEt₂Cl), could promote ethylene polymerizations that yielded extremely high molecular weight linear polymers, but were inactive for propylene polymerizations. The counterparts supported on MgCl₂ showed activities even for propylene polymerizations and had remarkably enhanced activities for ethylene polymerizations. In the presence of an electron donor such as ethylbenzoate, the MgCl₂‐supported manganese‐based catalysts yielded a highly isotactic polypropylene with a high molecular weight. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3733–3738, 2001     

Synthesis of a new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxycarbonyl)aminobenzenesulfonamide and its copolymerization with N‐phenyl maleimide

The new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxy‐ carbonyl)aminobenzenesulfonamide (MPBAS) (M₁) is synthesized using sulfadiazine as parent compound. It could be homopolymerized and copolymerized with N‐phenyl maleimide (NPMI) (M₂) by radical mechanism using AIBN as initiator at 60 °C in dimethylformamide. The new monomer MPBAS and polymers were identified by IR, element analysis and ¹H NMR in detail. The monomer reactivity ratios in copolymerization were determined by YBR method, and r₁ (MPBAS) = 2.39 ± 0.05, r₂ (NPMI) = 0.33 ± 0.02. In the presence of ammonium formate, benzyloxycarbonyl groups could be broken fluently from MPBAS segments of copolymer by catalytic transfer hydrogenation, and the copolymer with sulfadiazine side groups are recovered. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2548–2554, 2000     

Synthesis and evaluation of photoluminescent and electrochemical properties of new aromatic polyamides and polyimides with a kink 1,2‐phenylenediamine moiety

A series of novel triphenylamine‐containing aromatic polyamides and polyimides having a crank and twisted noncoplanar structures were synthesized in inherent viscosities of 0.14–0.64 dL/g and 0.11–0.67 dL/g, respectively. These polymers had useful levels of thermal stability associated with relatively high glass‐transition temperatures (174–311 °C). They exhibited strong UV–Vis absorption bands at around 300 nm in NMP solutions. The PL spectra of these polymers in NMP solutions (1 × 10^?5 M) showed maximum peaks around 396–479 nm. The hole‐transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammetry (CV) of the polymer films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited two reversible oxidation redox couples at potentials of 0.70–1.01 V and 1.10–1.46 V, respectively, vs. Ag/AgCl in acetonitrile solution. The polymer films revealed electrochromic characteristics, with a color change from neutral pale yellowish to green and then to a blue oxidized form at applied potentials ranging from 0.00 to 1.75 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2587–2603, 2006     

Axially Dissymmetric Chiral (R)‐N,W‐Bis(2‐hydroxy‐3,5‐ditert‐butyl‐arylmethyl)‐1, 1′‐binaphthalene‐2,2′‐diamine as Chiral Ligands in the Reaction of Diethylzinc to Aldehydes†

Chiral ligand (A)‐N,N′‐Bis(2‐hydroxy‐3,5‐di‐tert‐butyl‐arylmethyl)‐1,1′‐binaphthalene‐2,2′‐diamine derived from the reduction of Schiff base (R)‐2,2′‐bis (3,5‐di‐tert‐butyl‐2‐hydroxybenzylideneamino)‐1, 1′‐binaphthyl with LiAlH₄, is fairly effective in the asymmetric addition reaction of diethylzinc to aldehydes by which good yields (46%‐94%) of the corresponding sec‐alcohols can be obtained in moderate ee (51%‐79%) with R configuration for a variety of aldehydes.     

Determination and tissue distribution studies of dantrolene sodium with hydroxypropyl‐β‐cyclodextrin in rat tissue by HPLC/MS/MS

The established analytical method for determining the concentration of dantrolene sodium (Da) in rat tissues by HPLC/MS/MS technique was successfully applied to tissue distribution studies of Da in rats. Tissue homogenate samples were pretreated by protein precipitation with pre‐cooled methanol. Chromatographic separation was achieved on an Acquity HPLC column (Kromat Universil XB‐C₁₈, 2.1 × 150 mm, 3 μm). Mass spectrometry was conducted with an electrospray ionization interface in negative ionization mode and multiple reaction monitoring was used for quantitative analysis. The results showed that Da was rapidly and widely distributed in tissues and reached the maximum concentration within 0.5 h in all tissues after oral administration of Da–hydroxypropyl‐β‐cyclodextrin (DHC). It was then metabolized by liver and finally excreted from kidney,which indicated that DHC inclusion complex has better absorption and higher oral bioavailability than Da. The results also provided evidence for the safety and effectiveness of drug clinical application.     

Synthesis and Structure of MnCl2(HDpyF) (HDpyF = N,N′‐di(2‐pyridyl)formamidine): New Crystallographic Disorder and Bonding Mode of the HDpyF Ligand

The reaction of N,N′‐di(2‐pyridyl)formamidine (HDpyF) with MnCl₂‐4H₂O afforded the complex MnCl₂(HDpyF), which was characterized by X‐ray crystallography. The HDpyF ligand chelates to the Mn(II) center through the first and the third nitrogen atoms to form a six‐membered ring, leaving the second and the fourth nitrogen atoms uncoordinated. The HDpyF ligand is crystallographically disordered such that two different molecules can be solved. The neutral HDpyF ligand adopts the new s‐cis‐syn‐s‐trans conformation.     

Construction of a Highly Selective and Sensitive La(III) Sensor Based on N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea for Nano Level Monitoring of La(III) Ions

N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea (PMPT) was found to be a suitable neutral ion carrier for the construction of a highly selective and sensitive La(III) membrane sensor. Poly(vinyl chloride) (PVC) based membranes of PMPT with potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) as an anionic excluder and oleic acid (OA), dibutyl phthalate (DBP), benzyl acetate (BA) and o‐nitrophenyloctyl ether (NPOE) as plasticizing solvent mediators were constructed and investigated as La(III) membrane sensors. A membrane composed of PMPT‐PVC‐KTpClPB‐BA with the ratio 8.0 : 35.0 : 3.0 : 54.0 works well over a very wide concentration range (4.0×10^?8 to 1.0×10^?1 M) with a Nernstian slope of 19.6±0.2 mV per decade of activity between pH values of 4.0 and 9.0. The detection limit of the sensor was calculated to be 2.0×10^?8 M (ca. 3.0 ppb). The sensor displays very good discrimination toward La(III) ions with regard to most common metal ions and lanthanide ions. The proposed sensor shows a short response time for whole concentration range (ca. 12 s). For evaluation of the analytical applicability of the La(III) sensor, it was successfully used as an indicator electrode for the titration of La(III) ions with EDTA. It was also applied to the determination of fluoride content of two mouth wash preparation samples and monitoring of La(III) ions in some binary and ternary mixtures.