@article {2612,
	title = {Comparison of Dopants for Charge Exchange Ionization of Nonpolar Polycyclic Aromatic Hydrocarbons with Reversed-Phase LC-APPI-MS},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {20},
	number = {1},
	year = {2009},
	note = {ISI Document Delivery No.: 393RRTimes Cited: 4Cited Reference Count: 16Smith, Derek R. Robb, Damon B. Blades, Michael W.},
	month = {Jan},
	pages = {73-79},
	type = {Article},
	abstract = {Atmospheric pressure photoionization (APPI) is capable of ionizing nonpolar Compounds in LC/MS, through charge exchange reactions following photoionization of a dopant. Recently, several novel dopants-chlorobenzene, bromobenzene, 2,4-difluoroanisole, and 3-(trifluoromethyl)anisole-have been identified as having properties making them well-suited to serve as dopants for charge exchange ionization under reversed-phase LC conditions. Here, we report the results of experiments comparing their effectiveness to that of established dopants-toluene, anisole, and a toluene/anisole Mixture, for the charge exchange ionization of model nonpolar compounds-the 16 polycyclic aromatic hydrocarbons (PAHs) identified by the US EPA as priority pollutants-when using a conventional reversed-phase LC method. Chloro- and bromobenzene were found to be much more effective than toluene for all the PAHs, due to the relatively low reactivity of their photoions with the solvent. Their overall performance was also better than that of anisole, due to anisole{\textquoteright}s ineffectiveness toward higher-IE compounds. Further, the experiments revealed that anisole{\textquoteright}s performance for higher-IE compounds can be dramatically improved by introducing it as a dilute Solution in toluene, rather than neat. The two fluoroanisoles provided the highest overall sensitivity, by a slim margin, when introduced as dilute solutions in either chloro- or bromobenzene. (J Am Soc Mass Spectrom 2009, 20, 73-79) (C) 2009 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry},
	keywords = {ATMOSPHERIC-PRESSURE PHOTOIONIZATION, ENERGIES, LC/MS, MASS-SPECTROMETRY, PROTON, SOLVENT},
	isbn = {1044-0305},
	url = {<Go to ISI>://000262390900011},
	author = {Smith, D. R. and Robb, D. B. and Blades, M. W.}
}
@article {2649,
	title = {Free Energy Barrier Estimation for the Dissociation of Charged Protein Complexes in the Gas Phase},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {16},
	year = {2009},
	note = {ISI Document Delivery No.: 435ZUTimes Cited: 4Cited Reference Count: 29Wanasundara, Surajith N. Thachuk, Mark},
	month = {Apr},
	pages = {3814-3821},
	type = {Article},
	abstract = {Free energies are calculated for the protonated cytochrome c{\textquoteright} dimer ion in the gas phase as a function of the center of mass distance between the monomers. A number of different charge partitionings are examined as well as the behavior of the neutral complex. It is found that monomer unfolding competes with complex dissociation and that the relative importance of these two factors depends upon the charge partitioning in the complex. Symmetric charge partitionings preferentially suppress the dissociation barrier relative to unfolding, and complexes tend to dissociate promptly with little structural changes occurring in the monomers. Alternatively, asymmetric charge partitionings preferentially lower the barrier for monomer unfolding relative to the dissociation barrier. In this case, the monomer with the higher charge unfolds before the complex dissociates. For the homodimer considered here, this pathway has a large free energy barrier. The results can be rationalized using schematic two-dimensional free energy surfaces. Additionally, for large multimeric complexes, it is argued that the unfolding and subsequent charging of a single monomer is a favorable process, cooperatively lowering both the unfolding and dissociation barriers at the same time.},
	keywords = {ASSEMBLIES, ELECTROSPRAY-IONIZATION, MASS-SPECTROMETRY, MODEL, MOLECULAR-DYNAMICS, ORIGIN, PATHWAYS, SIMULATIONS, SYSTEMS, THERMAL-DISSOCIATION},
	isbn = {1089-5639},
	url = {<Go to ISI>://000265383200014},
	author = {Wanasundara, S. N. and Thachuk, M.}
}
@article {2426,
	title = {Products and kinetics of the reactions of an alkane monolayer and a terminal alkene monolayer with NO3 radicals},
	journal = {Journal of Geophysical Research-Atmospheres},
	volume = {114},
	year = {2009},
	note = {ISI Document Delivery No.: 401ZETimes Cited: 10Cited Reference Count: 95Gross, Simone Bertram, Allan K.},
	month = {Jan},
	pages = {14},
	type = {Article},
	abstract = {The reactions of an alkanethiol and a terminal alkenethiol self-assembled monolayer with NO3 radicals (in the presence of NO2 and O-2) were studied. For the alkane monolayer, infrared (IR) spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the formation of organonitrates (RONO2). The observation of organonitrates is in contrast to the recent X-ray photoelectron spectroscopy (XPS) data, which showed very little nitrogen-containing surface species. The identification of organonitrates may help explain why significant volatilization of the organic chain was not observed in recent studies of alkane monolayer oxidation by NO3 radicals. The reactive uptake coefficient (gamma) of NO3 on alkene monolayers determined in our study is higher than the values obtained in a recent study using liquid and solid alkene bulk films. A possible reason for this difference may be the location of the double bond at the interface. Using the g value determined in our studies, we show that under conditions where NO3 is high the lifetime of an alkene monolayer in the atmosphere may be short ( approximately 20 min). XPS, IR, and ToF-SIMS were used to identify surface functional groups after the oxidation of the alkene monolayers by NO3. The results are consistent with the formation of C-O, aldehyde/ketone, carboxylic groups, and nitrogen containing species.},
	keywords = {GAS-PHASE, HETEROGENEOUS OXIDATION, ION, MASS-SPECTROMETRY, NITROGEN-DIOXIDE, OH RADICALS, OLEIC-ACID, POLYCYCLIC AROMATIC-HYDROCARBONS, REACTIONS, RELATIVE RATE CONSTANTS, SELF-ASSEMBLED MONOLAYERS, VOLATILE ORGANIC-COMPOUNDS},
	isbn = {0148-0227},
	url = {<Go to ISI>://000262982300003},
	author = {Gross, S. and Bertram, A. K.}
}
@article {2184,
	title = {A dopant introduction device for atmospheric pressure photoionization with liquid chromatography/mass spectrometry},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {22},
	number = {22},
	year = {2008},
	note = {ISI Document Delivery No.: 376QHTimes Cited: 2Cited Reference Count: 16McCulloch, Ross D. Robb, Damon B. Blades, Michael W.},
	month = {Nov},
	pages = {3549-3554},
	type = {Article},
	abstract = {This technical note describes in detail the fabrication, operation and characterization of a pneumatically driven dopant introduction device, with a solvent reservoir capacity of 300 m L. Dopant flow rates and stability for this device are governed by the simple regulation of gas pressure rather than the progression of a stepper motor and syringe diameter, as is the case for typical infusion pumps. The device has the potential to provide days or even weeks of continuous, uninterrupted dopant flow at rates commonly adopted for atmospheric pressure photoionization (APPI) experiments without the need to replenish the dopant supply. Although not a refined instrumental design, this device was developed as an alternative cost-effective means of introducing stable dopant flow to an APPI source. The device was designed such that all components would be commercially available and easily procurable from common scientific part vendors. Figures and suggested part numbers are provided to allow those interested to fabricate similar devices to suit their individual experimental needs. Device characterization was performed while monitoring such factors as flow rate calibration, overall flow stability and reproducibility. In addition, a standard mixture of three polycyclic aromatic hydrocarbons was employed as a model sample for a typical reversed-phase liquid chromatography/ atmospheric pressure photoionization mass spectrometry (LC/APPI-MS) application in order to demonstrate device performance. Copyright (c) 2008 John Wiley \& Sons, Ltd.},
	keywords = {DA-APPI, IONIZATION, LC/MS, MASS-SPECTROMETRY, NONPOLAR COMPOUNDS},
	isbn = {0951-4198},
	url = {<Go to ISI>://000261197600011},
	author = {McCulloch, R. D. and Robb, D. B. and Blades, M. W.}
}
@article {2175,
	title = {Gas-phase proton-transfer pathways in protonated histidylglycine},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {22},
	number = {18},
	year = {2008},
	note = {ISI Document Delivery No.: 355WATimes Cited: 2Cited Reference Count: 23MacDonald, Brandon I. Thachuk, Mark},
	month = {Sep},
	pages = {2946-2954},
	type = {Article},
	abstract = {Pathways for proton transfer in the histidylglycine cation are examined in the gas-phase environment with the goal of understanding the mechanism by which protons may become mobile in proteins with basic amino acid residues. An extensive search of the potential energy surface is performed using density functional theory (DFT) methods. After corrections for zero-point energy are included, it is found that all the lowest energy barriers for proton transfer between the N-terminus and the imidazole ring have heights of only a few kcal/mol, while those between the imidazole ring and the backbone amide oxygen have heights of approximately 15 kcal/mol when the proton is moving from the ring to the backbone and only a few kcal/mol when moving from the backbone to the imidazole ring. In mass spectrometric techniques employing collision-induced dissociation to dissociate protein complex ions or to fragment peptides, these barriers can be overcome, and the protons mobilized. Copyright (C) 2008 John Wiley \& Sons, Ltd.},
	keywords = {COLLISION-INDUCED DISSOCIATION, fragmentation, IONIZATION, MASS-SPECTROMETRY, mobility, MODEL, ORIGIN, PEPTIDE IONS},
	isbn = {0951-4198},
	url = {<Go to ISI>://000259738700023},
	author = {MacDonald, B. I. and Thachuk, M.}
}
@article {2188,
	title = {Gene expression and metabolism in tomato fruit surface tissues},
	journal = {Plant Physiology},
	volume = {147},
	number = {2},
	year = {2008},
	note = {ISI Document Delivery No.: 308XITimes Cited: 36Cited Reference Count: 115Mintz-Oron, Shira Mandel, Tali Rogachev, Ilana Feldberg, Liron Lotan, Ofra Yativ, Merav Wang, Zhonghua Jetter, Reinhard Venger, Ilya Adato, Avital Aharoni, Asaph},
	month = {Jun},
	pages = {823-851},
	type = {Review},
	abstract = {The cuticle, covering the surface of all primary plant organs, plays important roles in plant development and protection against the biotic and abiotic environment. In contrast to vegetative organs, very little molecular information has been obtained regarding the surfaces of reproductive organs such as fleshy fruit. To broaden our knowledge related to fruit surface, comparative transcriptome and metabolome analyses were carried out on peel and flesh tissues during tomato ( Solanum lycopersicum) fruit development. Out of 574 peel-associated transcripts, 17\% were classified as putatively belonging to metabolic pathways generating cuticular components, such as wax, cutin, and phenylpropanoids. Orthologs of the Arabidopsis ( Arabidopsis thaliana) SHINE2 and MIXTA-LIKE regulatory factors, activating cutin and wax biosynthesis and fruit epidermal cell differentiation, respectively, were also predominantly expressed in the peel. Ultra-performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer and gas chromatography-mass spectrometry using a flame ionization detector identified 100 metabolites that are enriched in the peel tissue during development. These included flavonoids, glycoalkaloids, and amyrin-type pentacyclic triterpenoids as well as polar metabolites associated with cuticle and cell wall metabolism and protection against photooxidative stress. Combined results at both transcript and metabolite levels revealed that the formation of cuticular lipids precedes phenylpropanoid and flavonoid biosynthesis. Expression patterns of reporter genes driven by the upstream region of the wax-associated SlCER6 gene indicated progressive activity of this wax biosynthetic gene in both fruit exocarp and endocarp. Peel-associated genes identified in our study, together with comparative analysis of genes enriched in surface tissues of various other plant species, establish a springboard for future investigations of plant surface biology.},
	keywords = {ABC, ARABIDOPSIS-THALIANA, CELL ELONGATION, COTTON FIBER, CUTICULAR STRUCTURE, CUTIN BIOSYNTHESIS, FUNCTIONAL-CHARACTERIZATION, MASS-SPECTROMETRY, MYB TRANSCRIPTION FACTOR, TRANSPIRATION BARRIER PROPERTIES, TRANSPORTER GENE},
	isbn = {0032-0889},
	url = {<Go to ISI>://000256423600034},
	author = {Mintz-Oron, S. and Mandel, T. and Rogachev, I. and Feldberg, L. and Lotan, O. and Yativ, M. and Wang, Z. and Jetter, R. and Venger, I. and Adato, A. and Aharoni, A.}
}
@article {2232,
	title = {Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {19},
	number = {7},
	year = {2008},
	note = {ISI Document Delivery No.: 329LWTimes Cited: 7Cited Reference Count: 24Robb, Damon B. Smith, Derek R. Blades, Michael W.},
	month = {Jul},
	pages = {955-963},
	type = {Article},
	abstract = {Atmospheric pressure photoionization (APPI) using a dopant enables both polar and nonpolar compounds to be analyzed by LC/MS. To date, the charge exchange ionization pathway utilized for nonpolar compounds has only been efficient under restrictive conditions, mainly because the usual charge exchange reagent ions-the dopant photoions themselves-tend to be consumed in proton transfer reactions with solvent and/or dopant neutrals. This research aims to elucidate the factors affecting the reactivities of substituted-benzene dopant ions; another, overriding, objective is to discover new dopants for better implementing charge exchange ionization in reversed-phase LC/MS applications. The desirable properties for a charge exchange dopant include low reactivity of its photoions with solvent and dopant neutrals and high ionization energy (IE). Reactivity tests were performed for diverse substituted-benzene compounds, with substituents ranging from strongly electron withdrawing (EW) to strongly electron donating (ED). The results indicate that both the tendency of a dopant{\textquoteright}s photoions to be lost through proton transfer reactions and its IE depend on the electron donating /withdrawing properties of its substituent(s): ED groups decrease reactivity and IE, while EW groups increase reactivity and IE. Exceptions to the reactivity trend for dopants with ED groups occur when the substituent is itself acidic. All told, the desirable properties for a charge exchange dopant tend towards mutual exclusivity. Of the singlysubstituted benzenes tested, chloro- and brornobenzene provide the best compromise between low reactivity and high IE. Several fluoroanisoles, with counteracting EW and ED groups, may also provide improved performance relative to the established dopants.},
	keywords = {APPI, MASS-SPECTROMETRY, MECHANISM, MS, POTENTIALS, PROTON AFFINITY, SOLVENT},
	isbn = {1044-0305},
	url = {<Go to ISI>://000257870100007},
	author = {Robb, D. B. and Smith, D. R. and Blades, M. W.}
}
@article {2121,
	title = {Making connections for life: an in vivo map of the yeast interactome},
	journal = {Hfsp Journal},
	volume = {2},
	number = {5},
	year = {2008},
	note = {ISI Document Delivery No.: 355VHTimes Cited: 1Cited Reference Count: 28Kast, Juergen},
	month = {Oct},
	pages = {244-250},
	type = {Article},
	abstract = {Proteins are the true workhorses of any cell. To carry out specific tasks, they frequently bind other molecules in their surroundings. Due to their structural complexity and flexibility, the most diverse array of interactions is seen with other proteins. The different geometries and affinities available for such interactions typically bestow specific functions on proteins. Having available a map of protein - protein interactions is therefore of enormous importance for any researcher interested in gaining insight into biological systems at the level of cells and organisms. In a recent report, a novel approach has been employed that relies on the spontaneous folding of complementary enzyme fragments fused to two different proteins to test whether these interact in their actual cellular context [Tarassov et al., Science 320, 1465-1470 (2008)]. Genome- wide application of this protein- fragment complementation assay has resulted in the first map of the in vivo interactome of Saccharomyces cerevisiae. The current data show striking similarities but also significant differences to those obtained using other large- scale approaches for the same task. This warrants a general discussion of the current state of affairs of protein - protein interaction studies and foreseeable future trends, highlighting their significance for a variety of applications and their potential to revolutionize our understanding of the architecture and dynamics of biological systems.},
	keywords = {AMINO-ACIDS, CELL-CULTURE, COMPLEXES, CROSS-LINKING, IDENTIFICATION, MASS-SPECTROMETRY, PROTEIN-PROTEIN INTERACTIONS, QUANTIFICATION, QUANTITATION, SACCHAROMYCES-CEREVISIAE},
	isbn = {1955-2068},
	url = {<Go to ISI>://000259736700002},
	author = {Kast, J.}
}
@article {2334,
	title = {Quadrupole excitation of ions in linear quadrupole ion traps with added octopole fields},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {19},
	number = {4},
	year = {2008},
	note = {ISI Document Delivery No.: 289ZDTimes Cited: 2Cited Reference Count: 24Zhao, XianZhen Granot, Ori Douglas, D. J.},
	month = {Apr},
	pages = {510-519},
	type = {Article},
	abstract = {Modeling and experimental studies of quadrupole excitation of ions in linear quadrupole traps with added octopole fields are described. An approximate solution to the equations of motion of ions trapped in a quadrupole with added octopole and dodecapole fields, with quadrupole excitation and damping is given. The solutions give the steady-state or stationary amplitudes of oscillation with different excitation frequencies. Trajectory calculations of the oscillation amplitudes are also presented. The calculations show that there can be large changes in the amplitude of ion oscillation with small changes in excitation frequency, on both the low and high-frequency sides of a resonance. Results of experiments with quadrupole excitation of reserpine ions in linear quadrupole traps with 2.0\%, 2.6\%, and 4.0\% added octopole fields are given. It is found that as the excitation frequency is changed, two resonances are generally observed, which are attributed to the motion in the x and y directions. The two resonances can have quite different intensities. Sudden jumps or sharp sided resonances are not observed, although in some cases asymmetric resonances are seen. The calculated frequency differences between the two resonances are in approximate agreement with the experiments.},
	keywords = {CLOUD, fragmentation, FREQUENCIES, MASS-SPECTROMETRY, OF-FLIGHT SYSTEM, PAUL TRAP, PENNING TRAP, RESONANCES},
	isbn = {1044-0305},
	url = {<Go to ISI>://000255091500006},
	author = {Zhao, X. Z. and Granot, O. and Douglas, D. J.}
}
@article {1528,
	title = {Atmospheric pressure photoionization for ionization of both polar and nonpolar compounds in reversed-phase LC/MS},
	journal = {Analytical Chemistry},
	volume = {78},
	number = {23},
	year = {2006},
	note = {ISI Document Delivery No.: 110TZTimes Cited: 12Cited Reference Count: 9Robb, Damon B. Blades, Michael W.},
	month = {Dec},
	pages = {8162-8164},
	type = {Article},
	abstract = {Atmospheric pressure photoionization can provide high ionization efficiency simultaneously to both polar and nonpolar compounds delivered in reversed-phase solvent. The method to achieve this utilizes toluene as a dopant and simply requires that the solvent flow be limited so that reactions between toluene photoions and the organic component of the solvent are not driven to completion. Under these conditions, toluene photoions remain in the source for ionizing nonpolar compounds via charge exchange ( electron transfer), while protonated solvent ions are available for proton-transfer reactions with polar molecules. The reagent ion mixture is then suitable for ionizing a wide range of both polar and nonpolar compounds. The critical effect of solvent flow rate is demonstrated here with results for a test analyte, 9-methylanthracene, which may be ionized by either charge exchange or proton transfer. For a solvent of 50: 50 methanol/ water (v/v), lowering the flow from 200 to 50 mu L min(-1) results in a 10 x increase in charge exchange ionization efficiency-further flow reductions provide even greater enhancements. This method is compatible with sample delivery by direct infusion and micro- and narrow-bore LC, as well as conventional LC using a flow splitter.},
	keywords = {DOPANT, MASS-SPECTROMETRY, SOLVENT FLOW},
	isbn = {0003-2700},
	url = {<Go to ISI>://000242405300042},
	author = {Robb, D. B. and Blades, M. W.}
}
@article {1529,
	title = {Factors affecting primary ionization in dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC/MS},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {17},
	number = {2},
	year = {2006},
	note = {ISI Document Delivery No.: 012ZFTimes Cited: 25Cited Reference Count: 20},
	month = {Feb},
	pages = {130-138},
	type = {Article},
	abstract = {The sensitivity of dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC/MS is generally reduced at higher solvent flow rates. Theory suggests that quenching of excited-state precursors to the dopant ions, via collisions with vaporized solvent molecules, may be one mechanism responsible for this trend. To ascertain if the primary rate of ionization is affected by quenching, experiments were performed utilizing an ionization detector to determine the primary ion current generated by irradiating vaporized mixtures of toluene dopant and methanol solvent. The results indicate that no loss of primary ion current occurs as the solvent flow is increased, provided the dopant-to-solvent ratio is held constant. Additional primary ion current can always be generated by increasing the dopant flow rate and/or the lamp power. Thus, quenching of excited-state precursors to the dopant ions, leading to a reduction in the primary rate of ionization, is not the mechanism responsible for the observed loss of sensitivity at higher liquid solvent flow rates.},
	keywords = {DETECTOR, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, PERFORMANCE, PLASMA, SOLVENT FLOW},
	isbn = {1044-0305},
	url = {<Go to ISI>://000235378700003},
	author = {Robb, D. B. and Blades, M. W.}
}
@article {1436,
	title = {Glycosynthase-based synthesis of xylo-oligosaccharides using an engineered retaining xylanase from Cellulomonas fimi},
	journal = {Organic \& Biomolecular Chemistry},
	volume = {4},
	number = {10},
	year = {2006},
	note = {ISI Document Delivery No.: 041NHTimes Cited: 20Cited Reference Count: 39},
	pages = {2025-2032},
	type = {Article},
	abstract = {Glycosynthases are synthetic enzymes derived from retaining glycosidases in which the catalytic nucleophile has been replaced. The mutation allows irreversible glycosylation of sugar acceptors using glycosyl fluoride donors to afford oligosaccharides without any enzymatic hydrolysis. Glycosynthase technology has proven fruitful for the facile synthesis of useful oligosaccharides, therefore the expansion of the glycosynthase repertoire is of the utmost importance. Herein, we describe for the first time a glycosynthase, derived from a retaining xylanase, that synthesizes a range of xylo-oligosaccharides. The catalytic domain of the retaining endo-1,4-beta-xylanase from Cellulomonas fimi (CFXcd) was successfully converted to the corresponding glycosynthase by mutation of the catalytic nucleophile to a glycine residue. The mutant enzyme (CFXcd-E235G) was found to catalyze the transfer of a xylobiosyl moiety from alpha-xylobiosyl fluoride to either p-nitrophenyl beta-xylobioside or benzylthio beta-xylobioside to afford oligosaccharides ranging in length from tetra- to dodecasaccharides. These products were purified by high performance liquid chromatography in greater than 60\% combined yield. H-1 and C-13 NMR spectroscopic analyses of the isolated p-nitrophenyl xylotetraoside and p-nitrophenyl xylohexaoside revealed that CFXcd-E235G catalyzes both the regio- and stereo-selective synthesis of xylo-oligosaccharides containing, exclusively, beta-(1 {\textendash}> 4) linkages.},
	keywords = {4-GLYCANASE, BETA-1, DIRECTED EVOLUTION, EFFICIENT SYNTHESIS, ENZYMATIC-SYNTHESIS, GLYCOSIDASES, MASS-SPECTROMETRY, SPECIFICITY, SUBSTRATE, TRANSGLYCOSYLATION, XYLOOLIGOSACCHARIDES},
	isbn = {1477-0520},
	url = {<Go to ISI>://000237462400022},
	author = {Kim, Y. W. and Fox, D. T. and Hekmat, O. and Kantner, T. and McIntosh, L. P. and Warren, R. A. J. and Withers, S. G.}
}
@article {1441,
	title = {Linear quadrupoles with added hexapole fields},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {17},
	number = {8},
	year = {2006},
	note = {ISI Document Delivery No.: 071YITimes Cited: 14Cited Reference Count: 26Konenkov, Nikolai Londry, Frank Ding, Chuanfan Douglas, D. J.},
	month = {Aug},
	pages = {1063-1073},
	type = {Article},
	abstract = {Linear quadrupoles with added hexapole fields are described. The shifts in ion oscillation frequency caused by the addition of a hexapole field are calculated within the effective potential model. Methods to construct linear quadrupoles with added hexapole fields with exact electrode geometries and with round rods are discussed. A quadrupole with added hexapole field can be constructed with round rods by rotating two rods (say the y rods) towards an x rod. Computer simulations are used to investigate the possibility of mass analysis with quadrupoles with added hexapole fields. We find that a quadrupole with an added hexapole field in the range 2-12\% can provide mass analysis provided the dc is applied with the correct polarity and value. When a rod set is constructed with round rods, other multipoles in the potential degrade the peak shape, resolution and transmission. The largest of these after the quadrupole and hexapole are a dipole and octopole term. With round rod sets, the peak shape can be improved by using different diameters for the x and y rod pairs to minimize the octopole term in the potential and by injecting ions at the field center where the dipole term is zero. Calculations of the boundaries of the stability diagram for this case show the boundaries move out, relative to those of a pure quadrupole field, but remain sharp.},
	keywords = {EXCITATION, ION-TRAP, MASS-SPECTROMETRY, OCTOPOLE FIELDS},
	isbn = {1044-0305},
	url = {<Go to ISI>://000239639400003},
	author = {Konenkov, N. and Londry, F. and Ding, C. F. and Douglas, D. J.}
}
@article {1237,
	title = {Effects of solvent flow, dopant flow, and lamp current on dopant-assisted atmospheric pressure photoionization (DA-APPI) for LC-MS. Ionization via proton transfer},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {16},
	number = {8},
	year = {2005},
	note = {ISI Document Delivery No.: 952BFTimes Cited: 42Cited Reference Count: 37},
	month = {Aug},
	pages = {1275-1290},
	type = {Article},
	abstract = {In this paper, the effects of solvent flow, dopant flow, and lamp power on proton transfer ionization in dopant-assisted (DA) atmospheric pressure photoionization (APPI) are investigated. A broad theoretical framework is presented, describing the primary photoionization process, the formation of protonated-solvent cluster ions, and the balance between analyte ion creation via proton transfer and loss via recombination. The principal experimental test system utilized methanol as the solvent, toluene as the dopant, and acridine as the analyte. Comparisons are made between acridine and a less basic compound, 9-methylanthracene (9-MA). Experimental determinations of the trends in the analyte MH+ signal and the total ion current (TIC) with variations in the subject parameters are provided. Experimental results and theory demonstrate that both the analyte signal and the TIC approach asymptotic limits with increases in dopant flow and/or lamp current (two factors which dictate the rate of photoion generation). The data show that these limits are lowered at higher solvent flow rates. These results are attributed to the recombination loss process, the rate of which increases with the second power of ion concentration. We deduce that the recombination rate constant increases with solvent flow rate, a consequence of the growth of ion-solvent clusters. Cluster growth is also believed to be a factor in the dramatic loss of sensitivity for 9-MA that occurs as the solvent flow is raised, because larger protonated-solvent cluster ions have greater solvation energies and may be unreactive with compounds having low gas-phase basicity and/or low solvation energy.},
	keywords = {DETECTOR, GAS-PHASE, ION-SOURCE, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, METHANOL, PLASMA, SENSITIVITY, SOLVATION, SYSTEM},
	isbn = {1044-0305},
	url = {<Go to ISI>://000230975700009},
	author = {Robb, D. B. and Blades, M. W.}
}
@article {1149,
	title = {Quantitative proteomic analysis of sokotrasterol sulfate-stimulated primary human endothelial cells},
	journal = {Molecular \& Cellular Proteomics},
	volume = {4},
	number = {2},
	year = {2005},
	note = {ISI Document Delivery No.: 902UFTimes Cited: 9Cited Reference Count: 40},
	month = {Feb},
	pages = {191-204},
	type = {Article},
	abstract = {The endothelium forms a continuous monolayer at the interface between blood and tissue and contributes significantly to the sensing and transducing of signals between blood and tissue. New blood vessel formation, or angiogenesis, is initiated by the activation of endothelial cells and is an important process required for various pathological and physiological situations. This study used cleavable isotope-coded affinity tag reagents combined with mass spectrometry to investigate the molecular basis of a recently discovered angiogenesis-promoting steroid, sokotrasterol sulfate. Changes in the relative abundances of over 1000 proteins within human endothelial cells treated with sokotrasterol sulfate and vehicle-treated cells were identified and quantitated using this technique. A method that examines the entire ensemble of quantitative measurements was developed to identify proteins that showed a statistically significant change in relative abundance resulting from treatment with sokotrasterol sulfate. A total of 93 proteins was significantly up-regulated, and 37 were down-regulated in response to sokotrasterol sulfate stimulation of endothelial cells. Among the up-regulated proteins, several were identified that are novel to endothelial cells and are likely involved in cell communication and morphogenesis. These findings are consistent with a role for sokotrasterol sulfate in endothelial sprouting.},
	keywords = {CANCER, DIFFERENTIATION, EXPRESSION, GENE, GROWTH-FACTOR, ISCHEMIC-HEART-DISEASE, MASS-SPECTROMETRY, MOLECULE, THERAPEUTIC ANGIOGENESIS, VEGF},
	isbn = {1535-9476},
	url = {<Go to ISI>://000227381300008},
	author = {Karsan, A. and Pollet, I. and Yu, L. R. and Chan, K. C. and Conrads, T. P. and Lucas, D. A. and Andersen, R. J. and Veenstra, T.}
}
@article {918,
	title = {Arsenic speciation in human urine: are we all the same?},
	journal = {Toxicology and Applied Pharmacology},
	volume = {198},
	number = {3},
	year = {2004},
	note = {ISI Document Delivery No.: 844GRTimes Cited: 26Cited Reference Count: 34},
	month = {Aug},
	pages = {297-306},
	type = {Review},
	abstract = {we studied the arsenic speciation in human urine samples by using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). We investigated the arsenic speciation in the urine collected from nine volunteers during a 3-day period after a meal of blue mussels, Mytilus edulis. We also studied the effect of cooking on the arsenic speciation. Arsenobetaine and dimethylarsinic acid (DMAA) were the major arsenic metabolites found in the urine samples. Significant amounts of unknown metabolites were also detected. The excretion patterns of arsenic from individuals were generally similar except for two subjects. One of whom excreted high amounts of arsenobetaine even though no arsenic-rich food was eaten for 3 days before the experiment. The results reveal that we need a better understanding of the metabolism of arsenic compounds by human. (C) 2004 Elsevier Inc. All rights reserved.},
	keywords = {arsenic, arsenobetaine, arsenosugar, ENVIRONMENT, HPLC, ICP-MS, IDENTIFICATION, INGESTION, LIQUID-CHROMATOGRAPHY, MASS-SPECTROMETRY, METABOLITES, METHYLATED ARSENICALS, mussel, PRODUCTS, TRIVALENT, urine},
	isbn = {0041-008X},
	url = {<Go to ISI>://000223146600007},
	author = {Lai, V. W. M. and Sun, Y. M. and Ting, E. and Cullen, W. R. and Reimer, K. J.}
}
@article {942,
	title = {Continuous electrophoretic purification of individual analytes from multicomponent mixtures},
	journal = {Analytical Chemistry},
	volume = {76},
	number = {8},
	year = {2004},
	note = {ISI Document Delivery No.: 816FWTimes Cited: 10Cited Reference Count: 36},
	month = {Apr},
	pages = {2298-2305},
	type = {Article},
	abstract = {Individual analytes can be isolated from multicomponent mixtures and collected in the outlet vial by carrying out electrophoretic purification through a capillary column. Desired analytes are allowed to migrate continuously through the column under the electric field while undesired analytes are confined to the inlet vial by application of a hydrodynamic counter pressure. Using pressure ramping and buffer replenishment techniques, 18\% of the total amount present in a bulk sample can be purified when the resolution to the adjacent peak is similar to3. With a higher resolution, the yield could be further improved. Additionally, by periodically introducing fresh buffer into the sample, changes in pH and conductivity can be mediated, allowing higher purity (99.5\%) to be preserved in the collected fractions. With an additional reversed cycle of flow counterbalanced capillary electrophoresis, any individual component in a sample mixture can be purified providing it can be separated in an electrophoresis system.},
	keywords = {CAPILLARY-ZONE-ELECTROPHORESIS, CHIRAL SEPARATIONS, CHROMATOGRAPHY, ENANTIOMERS, FRACTION COLLECTOR, FREE-FLOW ELECTROPHORESIS, ISOELECTRIC-FOCUSING SEPARATION, MASS-SPECTROMETRY, MEMBRANE, PREPARATIVE-SCALE},
	isbn = {0003-2700},
	url = {<Go to ISI>://000221096800019},
	author = {McLaren, D. G. and Chen, D. D. Y.}
}
@article {687,
	title = {A quantitative study of continuous flow-counterbalanced capillary electrophoresis for sample purification},
	journal = {Electrophoresis},
	volume = {24},
	number = {17},
	year = {2003},
	note = {ISI Document Delivery No.: 723ZZTimes Cited: 10Cited Reference Count: 25},
	month = {Sep},
	pages = {2887-2895},
	type = {Article},
	abstract = {A systematic evaluation of continuous flow-counterbalanced capillary electrophoresis for microscale preparative applications is presented. The success of the technique was found to depend on the specific nature of the analyte and background electrolyte and was most heavily influenced by factors such as solution conductivity and rate of buffer depletion. The performance of the technique for the system studied was ultimately limited by contamination arising from changes in analyte mobilities during extended run times. Marked improvements in both purification rate and yield were observed using the zwitterionic buffer 2-(N-cyclohexylamino)ethanesulfonic acid when compared to similar runs carried out using a borate background electrolyte. A quantitative evaluation of the technique was performed for the analytes studied and the performance of the technique has been compared to fraction collection methods. The highest recovery achieved was 5.2\% of the fastest migrating component present in the original sample with a resolution of 9 to the adjacent peak and required 100 min under optimized conditions. Recovery could be further increased to 9.0\% in 120 min for the same analyte using pressure-ramped flow-counterbalanced capillary electrophoresis.},
	keywords = {amino acid, BUFFER, DESIGN, flow-counterbalanced capillary electrophoresis, FRACTION COLLECTOR, LASER-INDUCED FLUORESCENCE, MASS-SPECTROMETRY, MEMBRANE, MICELLAR ELECTROKINETIC CHROMATOGRAPHY, PLASMA, PURIFICATION, SAMPLE, SEPARATION, tetramethylrhodamine isothiocyanate, ZONE-ELECTROPHORESIS, zwitterionic buffer},
	isbn = {0173-0835},
	url = {<Go to ISI>://000185462800002},
	author = {McLaren, D. G. and Chen, D. D. Y.}
}
@article {723,
	title = {Resonance enhanced multiphoton dissociation of polycyclic aromatic hydrocarbons cations in an RF ion trap},
	journal = {Chemical Physics Letters},
	volume = {373},
	number = {3-4},
	year = {2003},
	note = {ISI Document Delivery No.: 681BGTimes Cited: 7Cited Reference Count: 35},
	month = {May},
	pages = {292-298},
	type = {Article},
	abstract = {We present a novel method for recording the absorption spectra of cations of non-volatile molecules using resonance enhanced multiphoton dissociation of trapped ions. Ions are produced through a 2-1aser desorption/ionization process in an RF ion trap mass-spectrometer. A third tunable visible laser induces fragmentation of the trapped ions with a yield dependent on the absorption cross-sections of the ions. Using this method we have recorded the visible absorption spectrum of two PAH isomers, phenanthrene and anthracene. (C) 2003 Elsevier Science B.V. All rights reserved.},
	keywords = {ENERGETICS, fragmentation, GAS-PHASE, IONIZATION, IR EMISSION, MASS-SPECTROMETRY, PAHs, PHOTODISSOCIATION, RADICAL CATIONS, SPECTROSCOPY},
	isbn = {0009-2614},
	url = {<Go to ISI>://000183016300010},
	author = {Rolland, D. and Specht, A. A. and Blades, M. W. and Hepburn, J. W.}
}
@article {361,
	title = {Determination of arsenic species in a freshwater crustacean Procambarus clarkii},
	journal = {Applied Organometallic Chemistry},
	volume = {16},
	number = {3},
	year = {2002},
	note = {ISI Document Delivery No.: 521YCTimes Cited: 14Cited Reference Count: 37},
	month = {Mar},
	pages = {123-132},
	type = {Article},
	abstract = {The arsenic species present in samples of the crayfish Procambarus clarkii caught in the area affected by the toxic mine-tailing spill at Aznalcollar (Seville, Southern Spain) were analyzed. The total arsenic contents ranged between 1.2 and 8.5 mug g(-1) dry mass (DM). With regard to the different species of arsenic, the highest concentrations were for inorganic arsenic (0.34-5.4 mug g(-1) DM), whereas arsenobetaine, unlike the situation found in marine fish products, was not the major arsenic species (0.16 +/- 0.09 mug g(-1) DM). Smaller concentrations were found of arsenosugars la (0.18 +/- 0.11 mug g(-1) DM), 1b (0.077 +/- 0.049 mug g(-1) DM), 1c (0.080 +/- 0.089 mug g(-1) DM), and 1d (0.14 +/- 0.13 mug g(-1) DM). The presence of two unknown arsenic species was revealed (U1: 0.058 +/- 0.058 mug g(-1) DM; U2: 0.12 +/- 0.12 mug g(-1) DM). No significant differences were seen with respect to the total arsenic contents between the sexes. However, significant differences in the total arsenic contents were revealed between the area affected by the spill and the area not affected, the contents being greater in the affected area. Copyright (C) 2002 John Wiley Sons, Ltd.},
	keywords = {arsenic, arsenic species, arsenobetaine, arsenosugars, ATOMIC-ABSORPTION SPECTROMETRY, CADMIUM, crayfish, crustacean, ENVIRONMENT, FISH, freshwater, LEAD, MASS-SPECTROMETRY, PERFORMANCE LIQUID-CHROMATOGRAPHY, SEAFOOD PRODUCTS, WATER MARSH},
	isbn = {0268-2605},
	url = {<Go to ISI>://000173868100002},
	author = {Devesa, V. and Suner, M. A. and Lai, V. W. M. and Granchinho, S. C. R. and Martinez, J. M. and Velez, D. and Cullen, W. R. and Montoro, R.}
}
@article {362,
	title = {Distribution of arsenic species in the freshwater crustacean Procambarus clarkii},
	journal = {Applied Organometallic Chemistry},
	volume = {16},
	number = {12},
	year = {2002},
	note = {ISI Document Delivery No.: 622PGTimes Cited: 2Cited Reference Count: 25},
	month = {Dec},
	pages = {692-700},
	type = {Article},
	abstract = {The concentrations of total arsenic and arsenic species in the complete organism of the crayfish Procambarus clarkii and its various parts (hepatopancreas, tail, and remaining parts) were analyzed in order to discover the distribution of arsenic and its species. With this information it will be possible to establish where the chemical forms of this metalloid tend to accumulate and what risks may derive from the contents and species present in the edible parts of this crustacean. The total arsenic content in the complete organism and in the various parts analyzed ranged from 2.5 to 12 mug g(-1) dry mass (DM), with inorganic arsenic representing 18 to 34\% of total arsenic. The arsenical composition varied according to the part of the crayfish considered. The hepatopancreas had the highest levels of total arsenic (9.2-12 mug g(-1) DM) and inorganic arsenic (2.7-3.2 mug g(-1) DM). The tail (edible part) had the lowest levels of both total arsenic (2.5-2.6 mug g(-1) DM) and inorganic arsenic (0.46-0.64 mug g(-1) DM). The predominant organoarsenical species were the dimethylarsinoylribosides: glycerol riboside in the hepatopancreas, sulfate riboside in the tail, and sulfonate and phosphate ribosides in the remaining parts. Copyright (C) 2002 John Wiley Sons, Ltd.},
	keywords = {arsenic, arsenic species, arsenosugars, ATOMIC-ABSORPTION SPECTROMETRY, BIOACCUMULATION, crayfish, DIGESTION, ENVIRONMENT, FISH, freshwater, heptopancreas, MASS-SPECTROMETRY, PERFORMANCE LIQUID-CHROMATOGRAPHY, PRODUCTS, SEAFOOD, SPECIATION, tail muscle},
	isbn = {0268-2605},
	url = {<Go to ISI>://000179655000002},
	author = {Devesa, V. and Suner, M. A. and Lai, V. W. M. and Granchinho, S. C. R. and Velez, D. and Cullen, W. R. and Martinez, J. M. and Montoro, R.}
}
@article {331,
	title = {High intensity ion beams from an atmospheric pressure inductively coupled plasma},
	journal = {Review of Scientific Instruments},
	volume = {73},
	number = {2},
	year = {2002},
	note = {ISI Document Delivery No.: 522WYTimes Cited: 2Cited Reference Count: 119th International Conference on Ion Sources (ICIS)SEP 03-07, 2001OAKLAND, CALIFORNIALawrence Berkeley Natl Lab, Axcells Technologies Inc, AccSys Technol Inc, Bergoz Instrumentat, Chabot Space \& Sci Ctr, Dehnel Consulting Ltd, GMW Associates, INTMAG EGUN IGUNPart 2},
	month = {Feb},
	pages = {884-886},
	type = {Proceedings Paper},
	abstract = {This work is directed towards substantially improving the sensitivity of an inductively coupled plasma mass spectrometer (ICP-MS). Ions produced in the ICP at atmospheric pressure have been extracted with comparatively high current densities. The conventional approach to ion extraction, based on a skimmed molecular beam, has been abandoned, and a high extraction field arrangement has been adopted. Although the new approach is not optimized, current densities more than 180 times greater than that of a conventional interface have been extracted and analyte sensitivities similar to10-100X greater than those reported previously for quadrupole ICP-MS have been measured. (C) 2002 American Institute of Physics.},
	keywords = {MASS-SPECTROMETRY},
	isbn = {0034-6748},
	url = {<Go to ISI>://000173921000120},
	author = {Al Moussalami, S. and Chen, W. and Collings, B. A. and Douglas, D. J.}
}
@article {439,
	title = {Hydrogen/deuterium exchange of myoglobin ions in a linear quadrupole ion trap},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {16},
	number = {20},
	year = {2002},
	note = {ISI Document Delivery No.: 604ADTimes Cited: 10Cited Reference Count: 26},
	pages = {1941-1945},
	type = {Article},
	abstract = {The hydrogen/deuterium (H/D) exchange of gas-phase ions of holo- and apo-myoglobin has been studied by confining the ions in a linear quadrupole ion trap with D2O or CD3OD at a pressure of several mTorr. Apo-myoglobin ions were formed by collision-induced dissociation of holomyoglobin ions between the orifice and skimmer of the ion sampling system. The exchange takes place on a time scale of seconds. Earlier cross section measurements have shown that holomyoglobin ions can have more compact structures than apo-myoglobin. Despite this, both holomyoglobin and apo-myoglobin in charge states +8 to +14 are found to exchange nearly the same number of hydrogens (ca. 103) in 4 s. It is possible the ions fold or unfold to new conformations on the much longer time scale of the exchange experiment compared with the cross section measurements. Copyright (C) 2002 John Wiley Sons, Ltd.},
	keywords = {COLLISION CROSS-SECTIONS, CYTOCHROME-C, GAS-PHASE, HEME, HOLOMYOGLOBIN, HYDROGEN-DEUTERIUM EXCHANGE, MASS-SPECTROMETRY, OF-FLIGHT, PROTEIN IONS, STABILITY, SYSTEM},
	isbn = {0951-4198},
	url = {<Go to ISI>://000178592700007},
	author = {Mao, D. M. and Ding, C. F. and Douglas, D. J.}
}
@article {431,
	title = {In situ extract ion/preconcentration of PCBs and PAHs from aqueous samples using polytetrafluoroethylene tubing},
	journal = {Analyst},
	volume = {127},
	number = {6},
	year = {2002},
	note = {ISI Document Delivery No.: 565YATimes Cited: 5Cited Reference Count: 23},
	month = {Jun},
	pages = {730-734},
	type = {Article},
	abstract = {In situ extraction/preconcentration of organics from water samples was accomplished using polytetrafluoroethylene (PTFE) tubing. Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were concentrated inside the tubing by flowing aqueous samples through it. The adsorbed PCBs and PAHs were then recovered by solvent desorption. The eluent was subsequently analyzed using gas chromatography with electron capture detection (GC-ECD) or gas chromatography with flame ionization detection (GC-FID). Multiple samples were simultaneously processed to concentrate organics onto several PTFE tubings. Analyses of seawater and surface microlayers using this technique demonstrated that organics in the surface microlayers were elevated with respect to those in the water column, consistent with previous findings.},
	keywords = {CHROMATOGRAPHY, MASS-SPECTROMETRY, MICROEXTRACTION, MICROLAYER, POLYCYCLIC AROMATIC-HYDROCARBONS, SOLID-PHASE EXTRACTION, WATER},
	isbn = {0003-2654},
	url = {<Go to ISI>://000176396800008},
	author = {Li, X. F. and Cullen, W. R. and Reimer, K. J.}
}
@article {5188,
	title = {An atmospheric pressure ion lens to improve electrospray ionization at low solution flow-rates},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {15},
	number = {22},
	year = {2001},
	note = {ISI Document Delivery No.: 492XYTimes Cited: 14Cited Reference Count: 20},
	pages = {2168-2175},
	type = {Article},
	abstract = {The performance of a reduced flow-rate electrospray ion source is substantially improved by the addition of an atmospheric pressure ion lens near the tip of the tapered sprayer. The magnitude and stability of ion signals, detected within a mass spectrometer, are significantly improved. In addition, the ion lens decreased the dependence of the ion signals on the sprayer position. These benefits are believed to be due to an improvement in the shape of the equipotential lines near the tip of the electrospray ion source. Copyright (C) 2001 John Wiley \& Sons, Ltd.},
	keywords = {CAPILLARY ZONE ELECTROPHORESIS, INTERFACE, MASS-SPECTROMETRY},
	isbn = {0951-4198},
	url = {<Go to ISI>://000172193900014},
	author = {Schneider, B. B. and Douglas, D. J. and Chen, D. D. Y.}
}
@article {5045,
	title = {Determination of trivalent methylated arsenicals in biological matrices},
	journal = {Toxicology and Applied Pharmacology},
	volume = {174},
	number = {3},
	year = {2001},
	note = {ISI Document Delivery No.: 464KTTimes Cited: 129Cited Reference Count: 67},
	month = {Aug},
	pages = {282-293},
	type = {Article},
	abstract = {The enzymatically catalyzed oxidative methylation of As yields methylated arsenicals that contain pentavalent As (As-V). Because trivalent As (As-III) is the favored substrate for this methyltransferase, methylated arsenicals containing As-V are reduced to trivalency in cells. Methylated arsenicals that contain As-III are extremely potent inhibitors of NADPH-dependent flavoprotein oxidoreductases and potent cytotoxins in many cell types. Therefore, the formation of methylated arsenicals that contain As-III may be properly regarded as an activation step, rather than a means of detoxification. Recognition of the role of methylated arsenicals that contain As-III in the toxicity and metabolism of As emphasizes the need for analytical methods to detect and quantify these species in biological samples. Hence, a method was developed to exploit pH-dependent differences in the generation of arsines from inorganic and methylated arsenicals that contain either As-V or As-III. Reduction with borohydride at pH 6 generated arsines from inorganic As-III, methyl As-III, and dimethyl As-III, but not from inorganic As-V, methyl As-V, and dimethyl As-V. Reduction with borohydride at pH 2 or lower generated arsines from arsenicals that contained either As-V or As-III. Arsines are trapped in a liquid nitrogen-cooled gas chromatographic trap, which is subsequently warmed to allow separation of the hydrides by their boiling points. Atomic absorption spectrophotometry is used to detect and quantify the arsines. The detection limits (ng As ml(-1)) for inorganic As-III, methyl As-III, and dimethyl As-III are 1.1, 1.2, and 6.5, respectively. This method has been applied to the analysis of arsenicals in water, human urine, and cultured cells. Both methyl As-III. and dimethyl As-III are detected in urine samples from individuals who chronically consumed inorganic As-contaminated water and in human cells exposed in vitro to inorganic As-III. The reliable quantitation of inorganic and methylated arsenicals that contain As-III. in biological samples will aid the study of the toxicity of these species and may provide a new biomarker of the effects of chronic exposure to As. (C) 2001 Academic Press.},
	keywords = {analysis, arsenic, atomic absorption spectrophotometry, biological matrices, CANCER MORTALITY, DIABETES-MELLITUS, DIMETHYLARSINIC ACID, DOSE-RESPONSE RELATIONSHIP, DRINKING-WATER, ENZYMATIC, HUMAN URINE, HYDRIDE GENERATION, MAMMALIAN SYSTEMS, MASS-SPECTROMETRY, METABOLISM, methylated arsenic, METHYLATION, MONOMETHYLARSONOUS ACID MMA(III), pentavalent arsenic, STABILITY, TOXICITY, trivalent arsenic},
	isbn = {0041-008X},
	url = {<Go to ISI>://000170532300010},
	author = {Del Razo, L. M. and Styblo, M. and Cullen, W. R. and Thomas, D. J.}
}
@article {5098,
	title = {Dissecting the electrostatic interactions and pH-dependent activity of a family 11 glycosidase},
	journal = {Biochemistry},
	volume = {40},
	number = {34},
	year = {2001},
	note = {ISI Document Delivery No.: 466CYTimes Cited: 56Cited Reference Count: 50},
	month = {Aug},
	pages = {10115-10139},
	type = {Article},
	abstract = {Previous studies of the low molecular mass family 11 xylanase from Bacillus circulans show that the ionization state of the nucleophile (GIu78, pK(a) 4.6) and the acid/base catalyst (Glu 172, pK(a) 6.7) gives rise to its pH-dependent activity profile. Inspection of the crystal structure of BCX reveals that Glu78 and Glu172 are in very similar environments and are surrounded by several chemically equivalent and highly conserved active site residues. Hence, there are no obvious reasons why their apparent pKa values are different. To address this question, a mutagenic approach was implemented to determine what features establish the pKa values (measured directly by C-13 NMR and indirectly by pH-dependent activity profiles) of these two catalytic carboxylic acids. Analysis of several BCX variants indicates that the ionized form of Glu78 is preferentially stabilized over that of Glu 172 in part by stronger hydrogen bonds contributed by two well-ordered residues, namely, Tyr69 and Gln127. In addition, theoretical pKa calculations show that Glu78 has a lower pKa value than Glu 172 due to a smaller desolvation energy and more favorable background interactions with permanent partial charges and ionizable groups within the protein. The pKa value of Glu172 is in turn elevated due to electrostatic repulsion from the negatively charged glutamate at position 78. The results also indicate that all of the conserved active site residues act concertedly in establishing the pKa values of Glu78 and Glu 172, with no particular residue being singly more important than any of the others. In general, residues that contribute positive charges and hydrogen bonds serve to lower the pKa values of Glu78 and Glu172. The degree to which a hydrogen bond lowers a pKa value is largely dependent on the length of the hydrogen bond (shorter bonds lower pKa values more) and the chemical nature of the donor (COOH > OH > CONH2). In contrast, neighboring carboxyl groups can either lower or raise the pKa values of the catalytic glutamic acids depending upon the electrostatic linkage of the ionization constants of the residues involved in the interaction. While the pH optimum of BCX can be shifted from -1.1 to +0.6 pH units by mutating neighboring residues within the active site, activity is usually compromised due to the loss of important ground and/or transition state interactions. These results suggest that the pH optima of an enzyme might be best engineered by making strategic amino acid substitutions, at positions outside of the "core" active site, that electrostatically influence catalytic residues without perturbing their immediate structural environment.},
	keywords = {ASSIGNMENTS, BACILLUS-CIRCULANS XYLANASE, CATALYSIS, GLYCOSYL-ENZYME INTERMEDIATE, KINETIC-ANALYSIS, MASS-SPECTROMETRY, MECHANISMS, NMR, PK(A), PROTEIN, SITE NUCLEOPHILE, structures},
	isbn = {0006-2960},
	url = {<Go to ISI>://000170627800014},
	author = {Joshi, M. D. and Sidhu, G. and Nielsen, J. E. and Brayer, G. D. and Withers, S. G. and McIntosh, L. P.}
}
@article {4920,
	title = {Electrospray ionization of alkali and alkaline earth metal species. Electrochemical oxidation and pH effects},
	journal = {Journal of Mass Spectrometry},
	volume = {35},
	number = {8},
	year = {2000},
	note = {ISI Document Delivery No.: 347MUTimes Cited: 7Cited Reference Count: 49},
	month = {Aug},
	pages = {981-989},
	type = {Article},
	abstract = {The utility of electrospray ionization mass spectrometry (ESI-MS) for characterizing dissolved metal species has generated considerable interest in the use of this technique for metal speciation, However, the development of accurate speciation methods based on ESI-R;IS requires a detailed understanding of the mechanisms by which dissolved metal species are ionized during electrospray. We report how the analysis of alkali and alkaline earth metal species pro,ides new information about some of the processes that affect electrospray ion yield. Selected metal ions and organic ligands were combined in 50:50 water-acetonitrile buffered with acetic acid or ammonium acetate and analyzed by flow injection ESI-MS using mild electrospray conditions. Species formed by alkali metal ions with thiol and oxygen-donating ligands were detected in acidic and neutral pH solutions. Electrochemical oxidation of N,N-diethyldithiocarbamate and glutathione during electrospray was indicated by detection of the corresponding disulfides as protonated or alkali metal species, The extent of ligand oxidation depended on solution pH and the dissociation constant of the thiol group, Tandem mass spectrometric experiments suggested that radical cations such as [NaL](+.) (where L = N,N -diethyldithiocarbamate) can be generated by in-source fragmentation of disulfide species. Greater complexation of alkali metals at neutral pH tvas indicated by a corresponding decrease in the relative abundance of the free metal ion, The number of alkali metal ions bound by glutathione and phthalic acid also increased with increasing pH, in accordance with thermodynamic equilibrium theory. Alkaline earth metal species were detected only in acidic solutions, the absence of 8-hydroxyquinoline complexes being attributed to their relative instability and subsequent dissociation during electrospray, Hence, accurate speciation by ESI-MS depends on experimental conditions and the intrinsic properties of each analyte, Copyright (C) 2000 John Wiley \&; Sons, Ltd.},
	keywords = {cell, COMPLEXES, electrochemical oxidation, ELECTROPHORESIS, electrospray ionization, ION-TRAP, MASS-SPECTROMETRY, metal speciation, OLIGONUCLEOTIDES, PEPTIDES, pH effects, PROTEINS, STOICHIOMETRY, thiol ligands, WATER},
	isbn = {1076-5174},
	url = {<Go to ISI>://000088934400006},
	author = {Ross, A. R. S. and Ikonomou, M. G. and Orians, K. J.}
}
@article {4365,
	title = {Conformation of native, reduced and [5-55](Ala) bovine pancreatic trypsin inhibitor in the gas phase},
	journal = {Rapid Communications in Mass Spectrometry},
	volume = {12},
	number = {1},
	year = {1998},
	note = {ISI Document Delivery No.: YQ873Times Cited: 14Cited Reference Count: 46},
	pages = {40-44},
	type = {Article},
	abstract = {Collision cross sections have been measured for gas phase ions of native oxidized bovine pancreatic trypsin inhibitor (BPTI), native reduced BPTI and a mutant form of BPTI containing a single disulphide bond between residues 5 and 55 ([5-55](Ala) BPTI). Cross sections for [5-55](Ala) BPTI and reduced BPTI were 9\% and 17\% greater respectively than those for native BPTI, Cross sections for native BPTI were smaller than previous estimates from the crystal structure but in reasonable agreement with values calculated from the radius of gyration determined by x-ray scattering from solution BPTI. The increase in cross section for reduced BPTI over native BPTI is similar to that seen in molecular dynamics simulations, The results show that the disulphide bonds of BPTI contribute to the folding of the gas phase ions, but that even in the absence of disulphide bonds the protein ions maintain compact structures. Comparisons to relative areas calculated from hydrodynamic radii of BPTI in solution suggest that when disulphide linkages are removed, BPTI in the gas phase unfolds less than BPTI in solution. (C) 1998 John Wiley \& Sons, Ltd.},
	keywords = {BPTI, DISULFIDE BOND, IONS, MASS-SPECTROMETRY, MOLECULAR-DYNAMICS SIMULATIONS, MYOGLOBIN, protein dynamics, STABILITY},
	isbn = {0951-4198},
	url = {<Go to ISI>://000071433000008},
	author = {Nesatiy, V. and Chen, Y. L. and Collings, B. A. and Douglas, D. J.}
}
@article {3636,
	title = {The early development of Fourier transform ion cyclotron resonance (PT-ICR) spectroscopy},
	journal = {Journal of Mass Spectrometry},
	volume = {31},
	number = {6},
	year = {1996},
	note = {ISI Document Delivery No.: UQ849Times Cited: 32Cited Reference Count: 44},
	month = {Jun},
	pages = {581-585},
	type = {Article},
	abstract = {The development of Fourier transform ion cyclotron resonance (FT-ICR) spectroscopy is traced from its 1973 conception by analogy to Fourier transform nuclear magnetic resonance (FT-NMR) spectroscopy and its 1974 experimental demonstration to its 1978 demonstration as the technique of choice for examining complex ion chemistry. The intellectual connections between conventional NMR and ICR and FT-NMR are described. The theoretical prediction and experimental demonstration of the many advantageous features of FT-ICR are described. Subsequent FT-ICR technique developments and applications are mentioned briefly.},
	keywords = {LINE-SHAPE, MASS-SPECTROMETRY},
	isbn = {1076-5174},
	url = {<Go to ISI>://A1996UQ84900001},
	author = {Comisarow, M. B. and Marshall, A. G.}
}
@article {3278,
	title = {TEMPLATION EFFECTS ON FORMATION OF A HEMICARCEPLEX},
	journal = {Supramolecular Chemistry},
	volume = {5},
	number = {1},
	year = {1995},
	note = {ISI Document Delivery No.: RX096Times Cited: 15Cited Reference Count: 36},
	pages = {31-37},
	type = {Article},
	abstract = {We have shown previously that the reaction to form carceplex 3 . guest has dramatic templation requirements where the best template molecule studied is one million times more effective at bridging the two bowl-shaped precursors than the poorest template. Here, we investigate the template requirements for the formation of hemicarceplex 4 . guest which is similar to carceplex 3 . guest in cavity size and shape. The two compounds differ in that 4 . guest lacks one of the four inter-bowl methylene bridges and thus has a portal and reduced symmetry relative to carceplex 3 . guest (C-2v vs D-4h). Thus, the template requirements for hemicarceplex 4 . guest are more stringent because the two howls can, in principle, misalign. We have found that despite these differences, the same template effect holds. We conclude that the same forces are at play in each reaction. These forces include 1) favorable van der Waals interactions between the template molecule and the forming cavity of the carceplex or hemicarceplex 2) unfavorable steric strain being imparted to the complex and 3) hydrogen bonds between the bowls. We also demonstrate the utility of matrix-assisted laser desorption ionization (MALDI) as a mild mass spectrometric technique for non-volatile organic compounds and complexes.},
	keywords = {4 PORTALS, BINDING, CAPTURE, CARCERANDS, CONSTRICTIVE, HOST-GUEST COMPLEXATION, LASER DESORPTION IONIZATION, MASS-SPECTROMETRY, POLYMERS, RECOGNITION, RELEASE},
	isbn = {1061-0278},
	url = {<Go to ISI>://A1995RX09600007},
	author = {Chopra, N. and Sherman, J. C.}
}
@article {3069,
	title = {GAS-PHASE ION CHEMISTRY OF (ETA(6)-C-C7H8)CR(CO)(3) BY FT-ICR SPECTROSCOPY - BETA-HYDRIDE TRANSFER IN ORGANOMETALLIC IONS},
	journal = {Journal of the American Chemical Society},
	volume = {116},
	number = {10},
	year = {1994},
	note = {ISI Document Delivery No.: NM988Times Cited: 4Cited Reference Count: 65},
	month = {May},
	pages = {4449-4454},
	type = {Article},
	abstract = {The gas-phase ion chemistry of eta(6)-cycloheptatriene chromium tricarbonyl was studied by Fourier transform ion cyclotron resonance spectroscopy. The well-known trend that fragment-ion reactivity toward the parent neutral increases with increasing electron deficiency on the metal atom was, in general, observed. However, the reactivity of the fragment ions from (eta(6)-c-C7H8)Cr(CO)(3) shows the order Cr+ > C5H6Cr+ > C7H8Cr+ approximate to C7H8Cr(CO)(+) > C7H8Cr(CO)(2)(+) > C7H8Cr(CO)(3)(+), in which C7H8Cr+ has an anomalously low reactivity. Similarly, the secondary ion-molecule product ion, (C7H8Cr)(2)(+), has an anomalously low reactivity when compared with that of (C7H8Cr)(2)(CO)(3)(+). A more quantitative analysis indicates that the ions C7H8Cr+, C7H8Cr2(CO)(+) and C7H8Cr2(CO)(2)(+) are less reactive than expected. All of these low reactivities can be explained by a beta-hydride shift from the cycloheptatriene ring to the chromium atom that converts the cycloheptatriene ligand into an aromatic tropylium ligand. The coordination hapticity to chromium changes from eta(6) to eta(7) + eta(1) and the electron deficiency of chromium drops by 2. Similarly, the reactivity of the fragment ion C5H6Cr+ implies it has a hydrido-pi-cyclopentadienyl structure. An additional driving force for these rearrangements appears to be the aromatization of the seven-membered cycloheptatriene ring to a tropylium ring and the aromatization of the five-membered cyclopentadiene ring to a cyclopentadienyl ring, as the fragment and secondary ion reactivity orders are normal in the otherwise analogous benzene chromium tricarbonyl and cyclopentadienyl vanadium tetracarbonyl systems. These latter systems have no possible corresponding aromatization reaction. Ions that have low reactivity and have metal-hydrogen bonds react with deuterium-labeled methanol to eliminate a molecule of molecular hydrogen in which one hydrogen atom comes from the hydroxyl group of methanol and the other hydrogen atom comes from the organometallic ion. In contrast, ions that have normal reactivity and do not have metal-hydrogen bonds give methanol adduct products when reacted with methanol.},
	keywords = {CARBONYL, CLUSTER FRAGMENTS, CYCLOTRON RESONANCE SPECTROSCOPY, FE+, INSERTION, MASS-SPECTROMETRY, MOLECULE REACTIONS, PRIMARY AMIDE COMPLEXES, REACTIVITY, SYSTEMS, TRANSITION-METAL IONS},
	isbn = {0002-7863},
	url = {<Go to ISI>://A1994NM98800037},
	author = {Kan, Z. Y. and Taylor, S. M. and Comisarow, M. B.}
}
@article {7175,
	title = {ATOMIC EXCITATION IN A JET-ASSISTED GLOW-DISCHARGE PLASMA PLUME},
	journal = {Spectrochimica Acta Part B-Atomic Spectroscopy},
	volume = {47},
	number = {11},
	year = {1992},
	note = {ISI Document Delivery No.: JN613Times Cited: 9Cited Reference Count: 41},
	month = {Oct},
	pages = {1287-1307},
	type = {Article},
	abstract = {A jet-assisted glow discharge emission source has previously been shown to suffer from self-absorption when the viewing axis is orientated in line with the support gas flow. This problem can be alleviated by rotating the viewing axis 90-degrees so that the absorption path length is significantly reduced; however, in viewing side-on, line-of-sight measurements of the plasma plume can be accomplished no closer than 25 mm from the sample surface due to geometry limitations. At this axial distance from the sample, the plume shows no Ar 11 emission, which differentiates it from the negative glow. Furthermore. evidence was found that the plume possesses features similar to flowing afterglows: energy is transported from the negative glow to the plume through argon metastable atoms. The collision of two metastable argon atoms produces ionization to the ground state of the argon ion, deactivation to the ground state of the argon atom and an energetic electron (7.32-7.68 eV) which is capable of exciting sputtered atoms. A strong correlation is observed between the square of the argon metastable population and the emission intensity for Cu I and Zn I as the jet flow rate is manipulated.},
	keywords = {ARGON, ICP, ION-SOURCE, LAMP, MASS-SPECTROMETRY, PERFORMANCE, STATE},
	isbn = {0584-8547},
	url = {<Go to ISI>://A1992JN61300005},
	author = {Banks, P. R. and Blades, M. W.}
}
