High accuracy mass measurement of peptides with internal calibration using a dual electrospray ionization sprayer system for protein identification

A dual-ESI-sprayer system was constructed and applied to achieve high accuracy of peptide mass measurement for protein identification by means of peptide mapping. Sample was introduced in one sprayer, and reference in the other, thus making internal calibration possible greatly enhancing the mass accuracy. Several samples were utilized to evaluate the reliability of this dual-ESI-sprayer system. The range of mass errors was 0.16-5.37 ppm. The peptide masses of tryptic digests of myoglobin (horse) were measured by the HPLC/dual-ESI-MS system, with mass deviations ranging from 0.01-7.67 ppm, and about 75% mass deviations below 5 ppm with 40% below 1[?]ppm. These peptide masses were utilized to perform database searching for protein identification, and compared to results obtained by external calibration. This comparison showed that the internal calibration provides a more reliable method of protein identification, with a much smaller number of required peptides for matching, and with less CPU time consumed for database searching.     

Eco-friendly synthesis of high silica zeolite Y with choline as green and innocent structure-directing agent

Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure-directing agents (OSDAs), which are chronically hazardous to humans and the environment. It is a growing trend to develop an eco-friendly and nuisanceless OSDA for zeolite synthesis. Herein, choline is employed as a non-toxic and green OSDA to synthesize high silica Y zeolite with SiO₂/Al₂O₃ ratios of 6.5–6.8. The prepared Y zeolite samples exhibited outstanding (hydro)thermal stability at ultrahigh temperature owing to the higher SiO₂/Al₂O₃ ratio. The XRF, SEM, ²⁹Si-NMR and ¹³Na+ results suggested that choline plays a structure-directing role in the synthesis of Y zeolite, while the feed molar fraction of Na⁺ is a crucial determinant for the framework SiO₂/Al₂O₃ ratio and the crystal morphology.     

Development, validation and transfer of a hydrophilic interaction liquid chromatography/tandem mass spectrometric method for the analysis of the tobacco-specific nitrosamine metabolite NNAL in human plasma at low picogram per milliliter concentrations

A highly sensitive bioanalytical method based on a simple liquid/liquid extraction and hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC/MS/MS) analysis has been developed, validated and transferred for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a tobacco-specific nitrosamine metabolite. Deuterated NNAL (NNAL-d(4)) was synthesized and used as the internal standard. This method can be used for the analysis of free and total NNAL (free NNAL plus NNAL-gluc) in K(3)-EDTA human plasma. Free NNAL and NNAL-d(4) are extracted from human plasma by liquid/liquid extraction. To analyze for total NNAL and the internal standard, a separate aliquot of the K(3)-EDTA human plasma is treated with beta-glucuronidase to deconjugate the NNAL-gluc; the total NNAL and internal standard are then extracted using liquid/liquid extraction. After drying down under nitrogen, the residue is reconstituted with acetonitrile and analyzed using positive ion electrospray and HILIC/MS/MS at a flow rate of 1.0 mL/min. The chromatographic run time is 1.0 min per injection, with retention time for both NNAL and NNAL-d(4) of 0.75 min with a capacity factor (k') of 2. The standard curve range for this assay is from 5.00-1000 pg/mL for both free and total NNAL, using a total plasma sample volume of 1.0 mL. The interday precision and accuracy of the quality control (QC) samples demonstrated <7.6% relative standard deviation (RSD) and <3.3% relative error (RE) for free NNAL. For total NNAL, the interday precision and accuracy of the QC samples demonstrated <11.7% RSD and <2.8% RE. Optimization of enzyme hydrolysis of NNAL-gluc is discussed in detail. The overall recoveries for free and total NNAL and IS were 68.2 and 71.5% (free) and 70.7 and 65.5% (total). No adverse matrix effects were noticed for this assay.     

Surface-enhanced Raman scattering in the ultraviolet spectral region: UV-SERS on rhodium and ruthenium electrodes

We report the first observation of surface-enhanced Raman scattering (SERS) excited with ultraviolet (UV) light from transition metal electrodes. Adsorbed pyridine and SCN- on rough rhodium (Rh) and ruthenium (Ru) electrodes, respectively, have been studied using 325 nm laser excitation. In contrast, the best enhancers in the visible and near infrared, silver and gold, do not produce UV-SERS. The experimental data of UV-SERS are in agreement with our preliminary theoretical calculation based on the electromagnetic enhancement mechanism. The enhancement factor is about 2 orders of magnitude for the Rh and Ru electrodes when they are excited at 325 nm.     

Catalysis by methyltrioxorhenium(VII): reduction of hydronium ions by europium(II) and reduction of perchlorate ions by europium(II) and chromium(II)

The title reactions occur stepwise, the first and fastest being MeReO3 + Eu2+ --> Re(VI) + Eu3+ (k298 = 2.7 x 10(4) L mol(-1) s(-1)), followed by rapid reduction of Re(VI) by Eu2+ to MeReO2. The latter species is reduced by a third Eu2+ to Re(IV), a metastable species characterized by an intense charge transfer band, epsilon410 = 910 L mol(-1) cm(-1) at pH 1; the rate constant for its formation is 61.3 L mol(-1) s(-1), independent of [H+]. Yet another reduction step occurs, during which hydrogen is evolved at a rate v = k[Re(IV)][Eu2+][H+](-1), with k = 2.56 s(-1) at mu = 0.33 mol L(-1). The 410 nm Re(IV) species bears no ionic charge on the basis of the kinetic salt effect. We attribute hydrogen evolution to a reaction between H-ReVO and H3O+, where the hydrido complex arises from the unimolecular rearrangement of Re(III)-OH in a reaction that cannot be detected directly. Chromium(II) ions do not evolve H2, despite E(Cr) degrees approximately E(EU) degrees. We attribute this lack of reactivity to the Re(IV) intermediate being captured as [Re(IV)-O-Cr(III)]2+, with both metals having substitutionally inert d3 electronic configurations. Hydrogen evolution occurs in chloride or triflate media; with perchlorate present, MeReO2 reduces perchlorate to chloride, as reported previously [Abu-Omar, M. M.; Espenson, J. H. Inorg. Chem. 1995, 34, 6239-6240].     

Infrared (1.2-1.6 microm) luminescence in Cr4+:Yb3Al5O12 single crystal with 940 nm diode pumping

Infrared (1.2-1.6 microm) luminescence in a ytterbium aluminium garnet (YbAG) crystal, doped with Cr (0.05at.%) ions, was investigated under CW laser diode pumping (lambda=940 nm). The Cr4+ emission band was observed with its peak at 1.34 microm and measured to be about 1.3 times with respect to Yb3+ IR luminescence (lambda=1.03 microm). We demonstrate that for the excitation wavelength of 940 nm Yb3+ ions act as sensitizers of the 3B2(3T2)-3B1(3A2) emission of Cr4+ ions. This crystal is promising as a high-efficient system for tunable laser (1.2-1.6 microm) output.     

Photochemical reaction mechanism of cyclobutanone: CASSCF study

The photochemical reaction channels of cyclobutanone have been studied at the CASSCF level with a 6‐31G* basis set. Starting from the n‐π* excited‐state (S₁) cyclobutanone, the three reactions can take place: decarbonylation (produce CO and cyclopropane or propylene), cycloelimination (produce ketene and ethylene), and ring expansion (produce oxacarbene). Our computation indicates that decarbonylation products CO and triplet trimethylene are formed on the triplet n‐π* excited state (T₁) in a stepwise way via a biradical intermediate after intersystem crossing (ISC) to T₁ from S₁. And, then, the triplet trimethylene undergoes a second ISC to the ground state (S₀) to produce the singlet trimethylene from which cyclopropane can be produced rapidly only overcoming a 1 to 2‐kcal/mol barrier while propylene can be formed as a secondary product. The cycloelimination products ketene and ethylene are formed on the S₀ in a concerted mechanism after internal conversion (IC) to S₀ from S₁ via a biradical conical intersection. The reaction channels corresponding to ring expansion on the S₀, T₁, and S₁ states have also been discussed, and the likeliest reaction path is that oxacarbene is formed on the ground state following S₁/S₀ internal conversion. The surface topology of cyclobutanone on the S₁ surface is characterized by a transition state separating the minimum from the S₁/S₀ conical intersection, which is consistent with the previous computations and can explain the wavelength dependence of the fluorescence emission yield. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Synthesis and properties of organosoluble poly(amide imide imide)s based on tetraimide dicarboxylic acid condensed from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 4,4′‐oxydianiline,and trimellitic anhydride and various aromatic diamines

A novel tetraimide dicarboxylic acid was synthesized with the ring‐opening addition of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 4,4′‐oxydianiline, and trimellitic anhydride in a 1/2/2 molar ratio in N‐methyl‐2‐pyrrolidone followed by azeotropic condensation to tetraimide dicarboxylic acid. A series of poly(amide imide imide)s (PAIIs) with inherent viscosities of 0.8–1.1 dL/g were prepared from tetraimide dicarboxylic acid with various aromatic diamines by direct polycondensation. Most of the PAIIs were readily soluble in a variety of amide polar solvents and even in less polar m‐cresol and pyridine. Solvent‐cast films had tensile strengths ranging from 99 to 106 MPa, elongations at break ranging from 8 to 13%, and initial moduli ranging from 2.0 to 2.3 GPa. The glass‐transition temperatures of these PAIIs were recorded at 244–276 °C. They had 10% weight losses at temperatures above 520 °C in air or nitrogen atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1092–1102, 2002     

PHOTOSENSORY TRANSDUCTION IN CILIATES. IV. MODULATION OF THE PHOTOMOVEMENT RESPONSE OF Blepharisma japonicum BY cGMP

Abstract— The effect of various modulators of cytoplasmic guanosine 3',5'-cyclic monophosphate (cGMP) level on the step-up photophobic responses in Blepharisma japonicum has been investigated to clarify the possible role of cGMP in the mechanism of photosensory signal transduction. Membrane-permeable analogs of cGMP, 8-bromo-guanosine 3',5'-cyclic monophosphate or dibutyryl cGMP, caused a marked dose-dependent prolongation of the latency for the photophobic response, resulting in inhibition of the photophobic response in Blepharisma japonicum. A similar effect was observed when cells were treated with 3'-isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, and pertussis toxin, a G-protein activity modulator. The G-protein activator, fluoroaluminate, and 6-anilino-5,8-quinolinedione (LY 83583), an agent which effectively lowers the cytoplasmic cGMP level, significantly enhanced the photoresponsiveness of these ciliates to visible light stimuli. These results suggest that cellular cGMP serves as a signal modulator in the photophobic response of Blepharisma japonicum.     

On-line concentration of s-triazine herbicides in micellar electrokinetic chromatography using a cationic surfactant

A new method for the simultaneous determination of anions (sulfate, nitrate, and chloride) and cations (sodium, ammonium, potassium, magnesium, and calcium) in acid rain waters was investigated using high-performance ion-exclusion/cation-exchange chromatography with conductimetric detection on a separation column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the hydrogen-form and an eluent comprising 1.5 mM sulfosalicylic acid–6 mM 18-crown-6 at pH 2.6, operated at 1.5 ml/min. Effective separation and highly sensitive conductimetric detection for the anions and the cations was achieved in about 14 min. Since the ionic balance (equivalents of anions/equivalents of cations) of acid rain waters of different pH (4.40–4.67) ranged from 0.97 to 0.94, evaluation of the water quality of acid rain was possible. This method was successfully applied to the simultaneous determination of the anions and the cations in acid rain transported from mainland China and North Korea to central Japan monitored by a meteorological satellite data analyzer.