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Electrospray Mass Spectra (electrospray + mass_spectrum)
Selected AbstractsElectrospray mass spectra of group 6 (Fischer) carbenes in the presence of electron-donor compoundsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2003M. A. Sierra Abstract Fischer carbene complexes 1,7 are not ionized under standard electrospray ionization (ESI) conditions. We report here that unsaturated chromium and tungsten (Fischer) carbene complexes can be ionized in an electrospray ion source in the presence of electron-donor compounds such as hydroquinone (HQ) or tetrathiafulvalene (TTF). The addition of these compounds, which seem to act as electron transfer agents, permits the recording and study of their ESI mass spectra in the negative mode of detection. Both chromium and tungsten(0) carbene complexes undergo in the first fragmentation stage a double simultaneous decarbonylation process. Copyright © 2003 John Wiley & Sons, Ltd. [source] Facile synthesis of pyridinium aryltetrachlorotellurates: crystal and molecular structure of [C5H6N][RTeCl4] (R = m -O2NC6H4, p -NCC6H4)APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2005Jens Beckmann Abstract Arylation of TeCl4 with arylboroxine,pyridine complexes [(RBO)3·C5H5N, where R = m -O2NC6H4 (1), p -O2NC6H4 (2), m -NCC6H4 (3), p -NCC6H4 (4)] and advantageous moisture provided good yields of the pyridinium aryltetrachlorotellurates [C5H6N][RTeCl4] [R = m -O2NC6H4 (5), p -O2NC6H4 (6), m -NCC6H4 (7), p -NCC6H4 (8)]. Compounds 5 and 8 have been investigated by X-ray crystallography. Key features of both crystal structures are intermolecular secondary Te,,,Cl interactions between the aryltetrachlorotellurate anions and weak association of the cations and anions. Electrospray mass spectra of compound 5 reveal that the associative interactions also play a role in solution. Copyright © 2005 John Wiley & Sons, Ltd. [source] Negative ion fragmentations of deprotonated peptides.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009The unusual case of isoAsp: a joint experimental, theoretical study. The following peptides have been examined in this study: GLDFG(OH), caeridin 1.1 [GLLDGLLGLGGL(NH2)], 11 Ala citropin 1.1 [GLFDVIKKVAAVIGGL(NH2)], Crinia angiotensin [APGDRIYVHPF(OH)] and their isoAsp isomers. It is not possible to differentiate between Asp- and isoAsp-containing peptides (used in this study) using negative ion electrospray mass spectrometry. This is because the isoAsp residue cleaves to give the same fragment anions as those formed by , and , backbone cleavage of Asp. The isoAsp fragmentations are as follows: RNHCH(CO2H),CHCONHR,,,,[RNH,(HO2CCHCHCONHR,)],,,RNH,+HO2CCHCHCONHR, and RNHCH(CO2H),CHCONHR,,,,[RNH,(HO2CCHCHCONHR,],,,,O2CCHCHCONHR,+RNH2. Calculations at the HF/6-31+G(d)//AM1 level of theory indicate that the first of these isoAsp cleavage processes is endothermic (by +115,kJ mol,1), while the second is exothermic (,85,kJ mol,1). The barrier to the highest transition state is 42,kJ mol,1. No diagnostic cleavage cations were observed in the electrospray mass spectra of the MH+ ion of the Asp- and isoAsp-containing peptides (used in this study) to allow differentiation between these two amino acid residues. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of negative ion electrospray mass spectra measured by seven tandem mass analyzers towards library formationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2008ina Volná A library of negative ion electrospray ionization mass spectra and tandem mass spectra (MS/MS) of sulfonated dyes has been developed for fast identification purposes. The uniform protocol has been elaborated and applied to the measurements of more than 50 anionic dyes. Three collision energies are selected in our protocol which ensures that at least one of them provides a suitable ratio of product ions to the precursor ion. The robustness is investigated with altered values of tuning parameters (e.g. the pressure of the nebulizing gas, the temperature and the flow rate of drying gas, and the mobile phase composition). The results of the inter-laboratory comparison of product ion mass spectra recorded on seven different tandem mass spectrometers (three ion traps, two triple quadrupoles and two hybrid quadrupole time of flight instruments) are presented for four representative anionic dyes , azo dye Acid Red 118, anthraquinone dye Acid Violet 43, triphenylmethane dye Acid Blue 1 and Al(III) metal-complex azo dye. The fragmentation patterns are almost identical for all tandem mass analyzers, only the ratios of product ions differ somewhat which confirms the possibility of spectra transfer among different mass analyzers with the goal of library formation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Rearrangement with formamide extrusion in the electrospray mass spectra of aminoacylbenzylaminesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2001Jing Chen Several aminoacylbenzylamines and their analogs were synthesized and analyzed by electrospray ionization mass spectrometry together with high-resolution and tandem mass spectrometric techniques. Fragment ions ([M,+,H,,,CH3NO]+) were observed and attributed to a transfer of the benzyl group to the N-terminal amino group, leading to elimination of formamide. The proposed mechanism is supported by accurate mass measurements, and by experiments on deuterium labeling and variations of functional groups. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||