Positive-ion electrospray ionization mass

Fig. 2. Individual positive ion electrospray ionization mass spectra taken at time (a) 0 and (b) 10 min into the reaction. The d isappearance of t he peak at m/z 649 and the growth of the products at m/z 191 and 397 are clearly evident.

Mass spectrometry Positive ion electrospray ionization mass spectrometry (ESl-MS) analysis was performed on a PE API 2000 triple quadrupole mass spectrometer (Sciex, Toronto, Canada). Spray voltage was set to 4.8 kV, and 30 V orifice voltage was applied. Samples were dissolved in a methanol-water (1 1, v/v) mixture containing 0.1% acetic acid, and 5 pL of sample was injected with a flow rate of 100 pL/min. The instmment was used in a Qj scan mode in the range of m/z 400-1700, with a step size of 0.3 amu and a dwell time of 0.5 ms. Other chimeric peptides in this study were purified and characterized in the same or a very similar way. 

Mirza, U.A. and Chait, B.T., Effects of anions on the positive ion electrospray ionization mass spectra of peptides and proteins. Anal. Chem., 66, 2898, 1994. 

Cherlet M, ScheUcens M, Croubels S, De Backer P, Quantitative multi-residue analysis of tetracyclines and their 4-epimers in pig tissues by high-performance liquid chromatography combined with positive ion electrospray ionization mass spectrometry, Anal. Chim. Acta 2003 492 199-213. 

The dark orange-brown crystalline compound is stable in air and soluble in CH2CI2, THF, and EtOH. Its positive ion ESI-MS shows only one peak at tn z = 631, with an isotopic distribution consistent with the fragment [M —Cl]. Positive ion electrospray ionization mass spectrometry is very useful in characterizing these compounds, but the axially coordinated Cl anion is easily lost during the fragmentation process, and only fragments that correspond to the species [M — Cl]" are observed. 

FIGURE 5.6 Positive ion electrospray ionization mass spectrometry (ESI-MS)/MS product ion spectrum of delphinidin 3-0-(2-0-p-D-glucopyranosyl-a-L-arabinopyranoside), the major anthocyanin of Beluga black lentils. The MS/MS spectrum was obtained by isolating and fragmenting the molecular ion [M]+ at mjz 597.1199. The ion at 303.0431 corresponds to the aglycon delphindin. (Reprinted from Takeoka, G.R., Dao, L.T., Tamura, H., Harden, L.A.,. Agric. Food Chem., 53, 4932-4937, 2005. With permission.)... 

Figure 5.62 Product-ion MS-MS spectra of the molecular ions from 8-hydroxy-2 -deoxyguanosine, obtained by (a) positive, and (b) negative ionization. Reprinted by permission of Elsevier Science from Comparison of negative- and positive-ion electrospray tandem mass spectrometry for the liquid chromatography-tandem mass spectrometry analysis of oxidized deoxynucleosides , by Hua, Y., Wainhaus, S. B., Yang, Y., Shen, L., Xiong, Y., Xu, X., Zhang, F. Bolton, J. L. and van Breemen, R. B., Journal of the American Society for Mass Spectrometry, Vol. 12, pp. 80-87, Copyright 2000 by the American Society for Mass Spectrometry.

Iwata, Y. T, Kanamori, T, Ohmae, Y., Tsujikawa, K., Inoue, H., and Kishi, T. (2003). Chiral analysis of amphetamine-type stimulants using reversed-polarity capillary electrophoresis/positive Ion electrospray Ionization tandem mass spectrometry. Electrophoresis 24, 1770—1776. 

Figure F2.4.1 Liquid chromatography/mass spectrometry (LC/MS) analysis of isomeric carotenes in a hexane extract from 0.5 ml human serum. Positive ion electrospray ionization MS was used on a quadrupole mass spectrometer with selected ion monitoring to record the molecular ions of lycopene, p-carotene, and a-carotene at m/z (mass-to-charge ratio) 536. A C30 HPLC column was used for separation with a gradient from methanol to methyl-ferf-butyl ether. The a -trans isomer of lycopene was detected at a retention time of 38.1 min and various c/ s isomers of lycopene eluted between 27 and 39 min. The all-frans isomers of a-carotene and P-carotene were detected at 17.3 and 19.3 min, respectively.

A second common linker is the acid cleavable linker. Treatment with 95% TFA cleaves the ligand. Evaporation and re-dissolution in acetonitrile prepares the sample for MS. For example, 50 pL of TFA was added to each vial, and the vials were left at room temperature for 60 minutes. The TFA was evaporated to dryness, and the sample re-dissolved in 25 uL of acetonitrile. Methanol is to be avoided at this point because methanolic TFA, even if dilute, is an effective methylating milieu. The mass spectrum is most readily obtained by positive ion electrospray ionization. But we also employ negative ion electrospray when advantageous. Flow injection analysis can be used for sample introduction but conventional or capillary LC provide better sensitivity and the opportunity to compare LC/UV and LC/MS profiles for more complete characterization. 

Figure 9.12 Direct electrospray ionization-mass spectrometry analysis of human erythrocyte plasma membrane phospholipids (A) A positive-ion electrospray ionization (ESI) mass spectrum of erythrocyte plasma membrane phospholipid extract showing 14 molecular species of glycerophospholipids and 4 molecular species of sphingomyelin (B) A negative-ion ESI mass spectrum of the same extract of plasma membrane phospholipids showing more than 25 molecular species of ethanolamine glycerophospholipids and 8 molecular species of serine and inositol glycerophospholipids. Reprinted with permission from Han, X. and Gross, R. W., Electrospray ionization mass spectroscopic analysis of human erythrocyte plasma membrane phospholipids, Proc. Natl Acad. Scl USA, 91(22), 10635-9. Copyright (1994) National Academy of Sciences, USA.

Table 19.1 Ions monitored for determination of niacin by isotope dilution mass spectrometry using positive electrospray ionization. Both natural and labelled nicotinic acid are protonated in positive ion electrospray ionization, giving quasi-molecular ions at mass-to-charge ratios (m/z) of 124 and 128, respectively, which can be monitored directly in selected ion recording (SIR) experiments and selected as the parent ions in multiple reaction monitoring (MRM) experiments. In MRM experiments protonated nicotinic acid can be induced to produce daughter ions at several other m/z values, but the given transitions are the ones with the highest signal intensity.

Harvey, G. J. and Dunphy, J. C. Characterisation of cationic, anionic, and nonionic surfactants by positive and negative ion electrospray ionization mass spectrometry. Proceedings of the 40th ASMS Conference on Mass Spectrometry and Allied Topics, Washington, DC, May 31-June 5, 1992. 

Murray KK. DNA sequencing by mass spectrometry. J Mass Spectrom. 1996 31 1203-15. Xiang Y, Abliz Z, Takayama M. Cleavage reactions of the complex ions derived from self-complementary deoxydinucleotides and alkali-metal ions using positive ion electrospray ionization with tandem mass spectrometry. J Am Soc Mass Spectrom. 2004 15 689-96. Boschenok J, Sheil MM. Electrospray tandem mass spectrometry of nucleotides. Rapid CommunMass Spectrom. 1996 10 144-9. 

Figure 6.2 Positive-ion electrospray ionization tandem mass spectra of choline lyso-glycerophospholipid regioisomers. Positive-ion ESI tandem MS analyses of sodiated 1-hexadecanoy 1-2-hydroxy-in-glycero-3-phosphocholine (a) and sodiated l-hydroxy-2-hexadecanoyl-in-glycero-3-phosphocholine (b) was performed on a TSQ mass spectrometer (Finnigan TSQ MAT 700). Colhsion activation was carried out with collision energy of 20 eV and gas pressure of 1 mTorr. The asterisks indicate the product ions at tn/z 335 in (a) and m/z 415 in (b) present in very low abundance. Han and Gross [22], Reproduced with permission of the American Chemical Society.

Stanford, L., Rodgers, R., Marshall, A., Czarnecki, J. and Wu, X. (2007). Compositional Characterization of Bitumen/Water Emulsion Films by Negative-and positive-Ion Electrospray Ionization Ion Cyclotron Resonance Mass Spectrometry, Energy Fuels Vol. 21(No.2) 963-972. 

Stanford, L.A. Rodgers, R.P. Marshall, A.G. Czamecki, J. Wu, X.A. Compositional Characterization of Bitu-mcn/Watcr Emulsion Films by Negative-and Positive-Ion Electrospray Ionization and Field Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2007,21,963-972. 

Kloos D, Derks RJE, Wijtmans M, Lingeman H, Mayboroda OA, Decider AM, Niessen WMA, Giera M (2012) Derivatization of the tricarboxylic acid cycle intermediates and analysis by online solid-phase extraction-liquid chromatography-mass spectrometry with positive-ion electrospray ionization. J ChromatogrA 1232 19-26... 

L. Konermann and D. J. Douglas. Unfolding of Proteins Monitored by Electrospray Ionization Mass Spectrometry A Comparison of Positive and Negative Ion Modes. J. Am. Soc. Mass Spectrom., 9(1998) 1248-1254. 

Also, a brief note has appeared concerning electrospray ionization mass spectrometry of mixtures of -carotene with ft- and with y-cyclodexlrin in aqueous methanol solutions. Whereas negative ion ESI produced 1 1 adduct ions of -carotene with both of the cyclodextrin isomers, positive ESI gave these adducts only in the case of ft-cyclodextrin302. 

Figure 5 Examples of Data Generated on an Electrospray Ionization Mass Spectrometer, (a) Proteins Typically Produce Positive, Multiply Charged Ions and (b) Oligonucleotides Generate Negative, Multiply Charged Ions. Inset are the Computer-Generated Molecular Weight Spectra...

Using electrospray ionization mass spectrometry in both positive and negative ion modes, the on-line scanning of the Morita-Baylis-Hillman reaction in the presence of imidazolium ionic liquids has been investigated. The interception of several supramolecular species indicated that ionic liquids co-catalyse the reactions by activating the aldehyde toward nucleophilic enolate attack and by stabilizing the zwitterionic species that act as the main intermediates.175... 

The majority of reports have used electrospray ionization mass spectroscopy (ESI-MS) as an analytical detection method because of its sensitivity and the soft namre of its ionization procedure, which generally only leads to the detection of the molecular ions of the positive library members. Many separation techniques have been coupled to ESI-MS, including affinity chromatography (49), size exclusion chromatography (50, 51), gel filtration (52), affinity capillary electrophoresis (53-58), capillary isoelectric focusing (59), immunoaffinity ultrafiltration (60), and immunoaffinity extraction (61). ESI-MS has also been used alone (62) to screen a small carbohydrate library. Other examples reported alternative analytical techniques such as MALDI MS, either alone (63, 64) or in conjunction with size exclusion methods (65), or HPLC coupled with immunoaffinity deletion (66). 

The presence of pentosyUiexosides, trisaccharides and tetrasaccharides has been reported in different wines using positive- and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (Cooper and Marshall 2001). Nevertheless, at present there are still a number of minor carbohydrates in wines without a conclusive identification. 

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