What protein charging (and Supercharging) reveal about the mechanism of electrospray ionization

Journal of the American Society for Mass Spectrometry

Volumn 25, Issue 10, 2014, Pages 1675-1693

  Ogorzalek Loo, Rachel R ^a,b,c   Lakshmanan, Rajeswari ^b,d   Loo, Joseph A ^a,b,c  

^a UNIVERSITY OF CALIFORNIA   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

^c UNIVERSITY OF CALIFORNIA   (United States)

^d BECKMAN COULTER INC   (United States)

Author keywords

Charge state distributions; Electrospray ionization; Protein conformation; Supercharging

Indexed keywords

ACIDITY; ALKALINITY; ELECTRIC CHARGE; ELECTRIC FIELDS; GASES; IONIZATION OF GASES; IONS; PHASE INTERFACES; PROTEINS; REACTION INTERMEDIATES;

CHARGE STATE DISTRIBUTION; CHARGING MECHANISM; EQUILIBRIUM PARTITIONING MODEL; GAS-PHASE REACTIONS; HIGH ELECTRIC FIELDS; LIMITED DYNAMIC RANGES; PROTEIN CONFORMATION; SUPERCHARGING;

ELECTROSPRAY IONIZATION;

ANION; BENZONITRILE; ION; PROTEIN; REAGENT; SOLVENT;

ACIDITY; AEROSOL; ARTICLE; CONCENTRATION (PARAMETERS); DENATURATION; ELECTROSPRAY; ELECTROSPRAY MASS SPECTROMETRY; EVAPORATION; FLOW RATE; GAS; HYPOTHESIS; IONIZATION; PROTEIN ANALYSIS; PROTEIN CHARGING; CHEMICAL MODEL; CHEMISTRY; PROCEDURES; PROTEIN CONFORMATION;

MODELS, CHEMICAL; PROTEIN CONFORMATION; PROTEINS; SPECTROMETRY, MASS, ELECTROSPRAY IONIZATION;

EID: 84918565850     PISSN: 10440305     EISSN: 18791123     Source Type: Journal    
DOI: 10.1007/s13361-014-0965-1     Document Type: Article

References (114)

1. Dole, M., Mack, L.L., Hines, R.L., Mobley, R.C., Ferguson, L.D., Alice, M.B.: Molecular beams of macroions. J. Chem. Phys. 49(5), 2240-2249 (1968)
2. Iribarne, J.V., Thomson, B.A.: On the evaporation of small ions from charged droplets. J. Chem. Phys. 64, 2287-2294 (1976)
3. Kebarle, P., Tang, L.: From ions in solution to ions in the gas phase - the mechanism of electrospray mass spectrometry. Anal. Chem. 65(22), A972-A986 (1993)
4. Fenn, J.B., Rosell, J., Nohmi, T., Shen, S., Banks, F.J.J.: Electrospray ion formation: desorption versus desertion. ACS Sym. Ser. 619, 60-80 (1996)
5. Fernandez de la Mora, J.: Electrospray ionization of large multiply charged species proceeds via Dole's charged residue mechanism. Anal. Chim. Acta. 406, 93-104 (2000)
6. Kebarle, P., Peschke, M.: On the mechanisms by which the charged droplets produced by electrospray lead to gas phase ions. Anal. Chim. Acta. 406, 11-35 (2000)
7. Cole, R.B.: Some tenets pertaining to electrospray ionization mass spectrometry. J. Mass Spectrom. 35, 763-772 (2000)
8. Marginean, I., Znamenskiy, V., Vertes, A.: Charge reduction in electrosprays: slender nanojets as intermediates. J. Phys. Chem. B 110, 6397-6404 (2006)
9. Kaltashov, I.A., Abzalimov, R.R.: Do ionic charges in ESI MS provide useful information on macromolecular structure? J. Am. Soc. Mass Spectrom. 19, 1239-1246 (2008)
10. Kebarle, P., Verkerk, U.H.: On the mechanism of electrospray ionization mass spectrometry (ESIMS). In: Cole, R.B. (ed.) Electrospray and MALDI Mass Spectrometry, pp. 3-48. Wiley, Hoboken (2010)
11. Labowsky, M.: A model for solvated ion emission from electrospray droplets. Rapid Commun. Mass Spectrom. 24, 3079-3091 (2010)
12. Konermann, L., Rodriguez, A., Liu, J.: On the formation of highly charged gaseous ions from unfolded proteins by electrospray ionization. Anal. Chem. 84, 6798-6804 (2012)
13. Consta, S., Malevanets, A.: Classification of the ejection mechanisms of charged macromolecules from liquid droplets. J. Chem. Phys. 138, 044314 (2013)
14. Kelly, M.A., Vestling, M.M., Fenselau, C.C., Smith, P.B.: Electrospray analysis of proteins: a comparison of positive-ion and negative-ion mass spectra at high and low pH. Org. Mass Spectrom. 27, 1143-1147 (1992)
15. Loo, J.A., Udseth, H.R., Smith, R.D.: Collision effects on the charge distribution of ions from large molecules, formed by electrospray ionization-mass spectrometry. Rapid Commun. Mass Spectrom. 2, 207-210 (1988)
16. LeBlanc, J.C.Y., Wang, J., Guevremont, R., Siu, K.W.M.: Electrospray mass spectra of protein cations formed in basic solutions. Org. Mass Spectrom. 29, 587-593 (1994)
17. Hiraoka, K., Murata, K., Kudaka, I.: Do the electrospray mass spectra reflect the ion concentrations in sample solution? J. Mass Spectrom. Soc. Jpn. 43, 127-138 (1995)
18. Mansoori, B.A., Volmer, D.A., Boyd, R.K.: 'Wrong-way-round' electrospray ionization of amino acids. Rapid Commun. Mass Spectrom. 11, 1120-1130 (1997)
19. Wang, G., Cole, R.B.: Disparity between solution-phase equilibria and charge state distributions in positive-ion electrospray mass spectrometry. Org. Mass Spectrom. 29, 419-427 (1994)
20. Grandori, R.: Origin of the conformation dependence of protein charge-state distributions in electrospray ionization mass spectrometry. J. Mass Spectrom. 38, 11-15 (2003)
21. Prakash, H., Mazumdar, S.: Direct correlation of the crystal structure of proteins with the maximum positive and negative charge states of gaseous protein ions produced by electrospray ionization. J. Am. Soc. Mass Spectrom. 16, 1409-1421 (2005)
22. Marchese, R., Grandori, R., Carloni, P., Raugei, S.: On the Zwitterionic nature of gas-phase peptides and protein ions. PLoS Comput. Biol. 6, e1000775 (2010)
23. Ogorzalek Loo, R.R., Smith, R.D.: Proton transfer reactions of multiply charged peptide and protein cations and anions. J. Mass Spectrom. 30, 339-347 (1995)
24. Chowdhury, S.K., Katta, V., Chait, B.T.: Probing conformational changes in proteins by mass spectrometry. J. Am. Chem. Soc. 112, 9012-9013 (1990)
25. Loo, J.A., Ogorzalek Loo, R.R., Udseth, H.R., Edmonds, C.G., Smith, R.D.: Solvent-induced conformational changes of polypeptides probed by electrospray ionization-mass spectrometry. Rapid Commun. Mass Spectrom. 5(3), 101-105 (1991)
26. Le Blanc, J.C.Y., Guevremont, R., Siu, K.W.M.: Electrospray mass spectrometry of some proteins and the aqueous solution acid/base equilibrium model in the negative ion detection mode. Int. J. Mass Spectrom. Ion Process. 125, 145-153 (1993)
27. Verkerk, U.H., Kebarle, P.: Ion-ion and ion-molecule reactions at the surface of proteins produced by nanospray. Information on the number of acidic residues and control of the number of ionized acidic and basic residues. J. Am. Soc. Mass Spectrom. 16, 1325-1341 (2005)
28. Juraschek, R., Dülcks, T., Karas, M.: Nanoelectrospray - more than just a minimized-flow electrospray ionization source. J. Am. Soc. Mass Spectrom. 10, 300-308 (1999)
29. Kaltashov, I.A., Mohimen, A.: Estimates of protein surface areas in solution by electrospray ionization mass spectrometry. Anal. Chem. 77, 5370-5379 (2005)
30. Winger, B.E., Light-Wahl, K.J., Ogorzalek Loo, R.R., Udseth, H.R., Smith, R.D.: Observation and implications of high mass-to-charge ratio ions from electrospray ionization mass spectrometry. J. Am. Soc. Mass Spectrom. 4, 536-545 (1993)
31. Siu, K.W.M., Guevremont, R., Le Blanc, J.C.Y., O'Brien, R.T., Berman, S.S.: Is droplet evaporation crucial in the mechanism of electrospray mass spectrometry? Org. Mass Spectrom. 28, 579-584 (1993)
32. Ke, F., Le Blanc, J.C.Y., Guevremont, R., Siu, K.W.M.: The effects of stearyl and cetyl alcohol on the electrospray mass spectrometry of proteins and their implications on the electrospray mechanism. Eur. Mass Spectrom. 1, 253-260 (1995)
33. Fenselau, C., Szilágyi, Z., Williams, T.J.: Intercharge distances in Zn7-metallothionein analyzed by nanospray on a quadrupole ion trap and molecular modeling. Mass Spectrom. Soc. Jpn. 48, 23-25 (2000)
34. Nesatyy, V.J.: Mass spectrometry evaluation of the solution and gas-phase binding properties of noncovalent protein complexes. Int. J. Mass Spectrom. 221, 147-161 (2002)
35. Li, Y., Cole, R.B.: Shifts in peptide and protein charge state distributions with varying spray tip orifice diameter in nanoelectrospray fourier transform ion cyclotron resonance mass spectrometry. Anal. Chem. 75, 5739-5746 (2003)
36. Šamalikova, M., Matecko, I., Müller, N., Grandori, R.: Interpreting conformational effects in protein nano-ESI-MS spectra. Anal. Bioanal. Chem. 378, 1112-1123 (2004)
37. Gabelica, V., Vreuls, C., Filee, P., Duval, V., Joris, B., DePauw, E.: Advantages and drawbacks of nanospray for studying noncovalent protein-DNA complexes by mass spectrometry. Rapid Commun. Mass Spectrom. 16, 1723-1728 (2002)
38. Benkestock, K., Sundqvist, G., Edlund, P.O., Roeraade, J.: Influence of droplet size, capillary-cone distance, and selected instrumental parameters for the analysis of noncovalent protein-ligand complexes by nano-electrospray ionization mass spectrometry. J. Mass Spectrom. 39, 1059-1067 (2004)
39. Cech, N.B., Enke, C.G.: Effect of affinity for droplet surfaces on the fraction of analyte molecules charged during electrospray droplet fission. Anal. Chem. 73, 4632-4639 (2001)
40. Konermann, L.: A minimalist model for exploring conformational effects on the electrospray charge state distribution of proteins. J. Phys. Chem. 111(23), 6534-6543 (2007)
41. Iavarone, A.T., Jurchen, J.C., Williams, E.R.: Supercharged protein and peptide ions formed by electrospray ionization. Anal. Chem. 73, 1455-1460 (2001)
42. Iavarone, A.T., Williams, E.R.: Supercharging in electrospray ionization: effects on signal and charge. Int. J. Mass Spectrom. 219, 63-72 (2002)
43. Iavarone, A.T., Williams, E.R.: Mechanism of charging and supercharging molecules in electrospray ionization. J. Am. Chem. Soc. 125, 2319-2327 (2003)
44. Flick, T.G., Williams, E.R.: Supercharging with trivalent metal ions in native mass spectrometry. J. Am. Soc. Mass Spectrom. 23, 1885-1895 (2012)
45. Sterling, H.J., Cassou, C.A., Susa, A.C., Williams, E.R.: Electrothermal supercharging of proteins in native electrospray ionization. Anal. Chem. 84, 3795-3801 (2012)
46. Hedges, J.B., Vahidi, S., Yue, X., Konermann, L.: Effects of ammonium bicarbonate on the electrospray mass spectra of proteins: evidence for bubble-induced unfolding. Anal. Chem. 85, 6469-6476 (2013)
47. Sterling, H.J., Williams, E.R.: Origin of supercharging in electrospray ionization of non-covalent complexes from aqueous solution. J. Am. Soc. Mass Spectrom. 20, 1933-1943 (2009)
48. Sterling, H.J., Kintzer, A.F., Feld, G.K., Cassou, C.A., Krantz, B.K., Williams, E.R.: Supercharging protein complexes from aqueous solution disrupts their native conformations. J. Am. Soc. Mass Spectrom. 23, 191-200 (2011)
49. Šamalikova, M., Grandori, R.: Protein charge-state distributions in electrospray-ionization mass spectrometry do not appear to be limited by the surface tension of the solvent. J. Am. Chem. Soc. 125, 13352-13353 (2003)
50. Brahim, B., Alves, S., Cole, R.B., Tabet, J.-C.: Charge enhancement of single-stranded dna in negative electrospray ionization using the supercharging reagent meta-nitrobenzyl alcohol. J. Am. Soc. Mass Spectrom. 24, 1988-1996 (2013)
51. Šamalikova, M., Grandori, R.: Testing the role of solvent surface tension in protein ionization by electrospray. J. Mass Spectrom. 40(4), 503-510 (2005)
52. Gardner, H.A., Sward, G.G.: Paint Testing Manual, p. 173. ASTM International, Lutherville-Timonium (1972)
53. Lomeli, S.H., Yin, S., Ogorzalek Loo, R.R., Loo, J.A.: Increasing charge while preserving noncovalent protein complexes for ESI-MS. J. Am. Soc. Mass Spectrom. 20, 593-596 (2009)
54. Lomeli, S.H., Peng, I.X., Yin, S., Ogorzalek Loo, R.R., Loo, J.A.: New reagents for increasing ESI multiple charging of proteins and protein complexes. J. Am. Soc. Mass Spectrom. 21, 127-131 (2010)
55. Yin, S., Loo, J.A.: Elucidating the site of protein-ATP binding by top-down mass spectrometry. J. Am. Soc. Mass Spectrom. 21(6), 899-907 (2010)
56. van Duijn, E.: Current limitations in native mass spectrometry based structural biology. J. Am. Soc. Mass Spectrom. 21, 971-978 (2010)
57. Enyenihi, A.A., Yang, H., Ytterberg, A.J., Lyutvinskiy, Y., Zubarev, R.A.: Heme binding in gas-phase holo-myoglobin cations: distal becomes proximal? J. Am. Soc. Mass Spectrom. 22, 1763-1770 (2011)
58. Sterling, H.J., Daly, M.P., Feld, G.K., Thoren, K.L., Kintzer, A.F., Krantz, B.A., Williams, E.R.: Effects of supercharging reagents on noncovalent complex structure in electrospray ionization from aqueous solutions. J. Am. Soc. Mass Spectrom. 21, 1762-1774 (2010)
59. Merenbloom, S.I., Flick, T.G., Williams, E.R.: How hot are your ions in TWAVE ion mobility spectrometry? J. Am. Soc. Mass Spectrom. 23, 553-562 (2012)
60. Sterling, H.J., Prell, J.S., Cassou, C.A., Williams, E.R.: Protein conformation and supercharging with DMSO from aqueous solution. J. Am. Soc. Mass Spectrom. 22, 1178-1186 (2011)
61. Hogan Jr., C.J., Ogorzalek Loo, R.R., Loo, J.A., Fernández de la Mora, J.: Ion mobility-mass spectrometry of phosphorylase B ions generated with supercharging reagents but in charge-reducing buffer. Phys. Chem. Chem. Phys. 12, 13476-13483 (2010)
62. Valentine, S.J., Counterman, A.E., Clemmer, D.E.: Conformer-dependent proton-transfer reactions of ubiquitin ions. J. Am. Soc. Mass Spectrom. 8, 954-961 (1997)
63. Loo, J.A., Lomeli, S.H., Ogorzalek Loo, R.R.: Factors that promote ESI multiple charging for proteins. Proceedings of the 58th ASMS Conference on Mass Spectrometry and Allied Topics, Salt Lake City, UT, May 23-27 (2010)
64. Ogorzalek Loo, R.R., Lakshmanan, R., Zhang, J., Loo, J.A.: Supercharging and subcharging proteins and protein complexes to explore electrospray ionization. Proceedings of the 60th ASMS Conference on Mass Spectrometry and Allied Topics, Vancouver, BC, Canada, May 21-24 (2012)
65. Ogorzalek Loo, R.R., Smith, R.D.: Investigation of the gas-phase structure of electrosprayed proteins using ion-molecule reactions. J. Am. Soc. Mass Spectrom. 5, 207-220 (1994)
66. Konermann, L., Douglas, D.J.: Acid-induced unfolding of cytochrome c at different methanol concentrations: electrospray ionization mass spectrometry specifically monitors changes in the tertiary structure. Biochemistry 36, 12296-13302 (1997)
67. Grimm, R.L., Beauchamp, J.L.: Evaporation and discharge dynamics of highly charged multicomponent droplets generated by electrospray ionization. J. Phys. Chem. A 114, 1411-1419 (2010)
68. Douglass, K.A., Venter, A.R.: Investigating the role of adducts in protein supercharging with sulfolane. J. Am. Soc. Mass Spectrom. 23, 489-497 (2012)
69. Ogorzalek Loo, R.R., Dales, N., Andrews, P.C.: The effect of detergents on proteins analyzed by electrospray ionization. In: Chapman, J.R. (ed.) Methods in Molecular Biology: Protein and Peptide Analysis by Mass Spectrometry, vol. 61, pp. 141-160. Humana Press, Totowa (1996)
70. Barrera, N.P., Di Bartolo, N., Booth, P.J., Robinson, C.V.: Micelles protect membrane complexes from solution to vacuum. Science 321(5886), 243-250 (2008)
71. Laurence, C., Gal, J.-F.: Lewis Basicity and Affinity Scales. Wiley, Chichester (2010)
72. Aslam, M.H., Collier, G., Shorter, J.: The influence of the solvent on organic reactivity. Part 4. Spectroscopic parameters of Lewis basicity and acidity of hydroxylic solvents. A comprehensive correlation analysis of the log k values for the reactions of diazodiphenylmethane with benzoic acid in aprotic and hydroxylic solvents at 37 °C. J. Chem. Soc. Perkin Trans. 2, 1572-1576 (1981)
73. Mirza, U.A., Chait, B.T.: Effects of anions on the positive ion electrospray ionization mass spectra of peptides and proteins. Anal. Chem. 66(18), 2898-2904 (1994)
74. Liu, X., Cole, R.B.: A new model for multiply charged adduct formation between peptides and anions in electrospray mass spectrometry. J. Am. Soc. Mass Spectrom. 22, 2125-2136 (2011)
75. Tjernberg, A., Markova, N., Griffiths, W.J., Hallen, D.: DMSO-related effects in protein characterization. J. Biomol. Screen. 11(2), 131-137 (2006)
76. Valeja, S.G., Tipton, J.D., Emmett, M.R., Marshall, A.G.: New reagents for enhanced liquid chromatographic separation and charging of intact protein ions for electrospray ionization mass spectrometry. Anal. Chem. 82, 7515-7519 (2010)
77. Landreh, M., Alvelius, G., Johansson, J., Jörnvall, H.: Protective effects of dimethyl sulfoxide on labile protein interactions during electrospray ionization. Anal. Chem. 85, 4135-4139 (2014)
78. Lengqvist, J., Griffiths, W.J., Perlmann, T., Sjovall, J.: Detection of a receptor-ligand non-covalent complex using a triple quadrupole mass spectrometer. Rapid Commun. Mass Spectrom. 16, 2003-2206 (2002)
79. Meyer, J.G., Komives, E.A.: Charge state consolidation during electrospray ionization improves peptide identification by tandem mass spectrometry. J. Am. Soc. Mass Spectrom. 23, 1390-1399 (2012)
80. Cech, N.B., Enke, C.G.: Practical implications of some recent studies in electrospray ionization fundamentals. Mass Spectrom. Rev. 20, 362-387 (2001)
81. Pan, P., McLuckey, S.A.: Electrospray ionization of protein mixtures at low pH. Anal. Chem. 75, 1491-1499 (2003)
82. Loo, J.A., Ogorzalek Loo, R.R.: Desolvation of Noncovalently-Bound Complex Ions for ESI-MS Analysis. Proceedings of the 43rd ASMS Conference on Mass Spectrometry and Allied Topics, Atlanta, GA, May 21-26 (1995)
83. Kostiainen, R., Bruins, A.P.: Effect of multiple sprayers on dynamic range and flow rate limitations in electrospray and ionspray mass spectrometry. Rapid Commun. Mass Spectrom. 8, 549-558 (1994)
84. Stahnke, H., Kittlaus, S., Kempe, G., Alder, L.: Reduction of matrix effects in liquid chromatography-electrospray ionization-mass spectrometry by dilution of the sample extracts: how much dilution is needed? Anal. Chem. 84, 1474-1482 (2012)
85. Kuprowski, M.C., Konermann, L.: Signal response of coexisting protein conformers in electrospray mass spectrometry. Anal. Chem. 79, 2499-2506 (2007)
86. Wang, G., Cole, R.B.: Mechanistic interpretation of the dependence of charge state distributions on analyte concentrations in electrospray ionization mass spectrometry. Anal. Chem. 67, 2892-2900 (1995)
87. Yuill, E.M., Sa, N., Ray, S.J., Hieftje, G.M., Baker, L.A.: Electrospray ionization from nanopipette emitters with tip diameters of less than 100 nm. Anal. Chem. 85, 8498-8502 (2013)
88. Takáts, Z., Wiseman, J.M., Gologan, B., Cooks, R.G.: Mass spectrometry sampling under ambient conditions with desorption electrospray ionization. Science 306(5695), 471-473 (2004)
89. Liu, Y., Miao, Z., Lakshmanan, R., Ogorzalek Loo, R.R., Loo, J.A., Chen, H.: Signal and charge enhancement for protein analysis by liquid chromatography-mass spectrometry with desorption electrospray ionization. Int. J. Mass Spectrom. 325/327, 161-166 (2012)
90. Ferguson, C.N., Benchaar, S.A., Miao, Z., Loo, J.A., Chen, H.: Direct ionization of large proteins and protein complexes by desorption electrospray ionization-mass spectrometry. Anal. Chem. 83, 6468-6473 (2011)
91. Pagnotti, V.S., Inutan, E.D., Marshall, D.D., McEwen, C.N., Trimpin, S.: Inlet ionization: a new highly sensitive approach for liquid chromatography/mass spectrometry of small and large molecules. Anal. Chem. 83, 7591-7594 (2011)
92. Pagnotti, V.S., Chubatyi, N.D., McEwen, C.N.: Solvent assisted inlet ionization: an ultrasensitive new liquid introduction ionization method for mass spectrometry. Anal. Chem. 83, 3981-3985 (2011)
93. Li, J., Inutan, E.D., Wang, B., Lietz, C.B., Green, D.R., Manly, C.D., Richards, A.L., Marshall, D.D., Lingenfelter, S., Ren, Y., Trimpin, S.: Matrix assisted ionization: new aromatic and nonaromatic matrix compounds producing multiply charged lipid, peptide, and protein ions in the positive and negative mode observed directly from surfaces. J. Am. Soc. Mass Spectrom. 23(10), 1625-1643 (2012)
94. Heron, S.R., Wilson, R., Shaffer, S.A., Goodlett, D.R., Cooper, M.M.: Surface acoustic wave nebulization of peptides as a microfluidic interface for mass spectrometry. Anal. Chem. 82, 3985-3989 (2010)
95. Venter, A., Sojka, P.E., Cooks, R.G.: Droplet dynamics and ionization mechanisms in desorption electrospray ionization mass spectrometry. Anal. Chem. 78, 8549-8555 (2006)
96. Douglass, K.A., Venter, A.R.: Protein analysis by desorption electrospray ionization mass spectrometry and related methods. J. Mass Spectrom. 48, 553-560 (2013)
97. Fernández de la Mora, J., Loscertales, I.G.: The current emitted by highly conducting Taylor cones. J. Fluid Mech. 260, 155-184 (1994)
98. Gomez, A., Tang, K.: Charge and fission of droplets in electrostatic sprays. Phys. Fluids 6, 404-414 (1994)
99. Schmidt, A., Karas, M., Dülcks, T.: Effect of different solution flow rates on analyte ion signals in nano-ESI MS, or: when does ESI turn into nano-ESI? J. Am. Soc. Mass Spectrom. 14, 492-500 (2003)
100. Miladinovic, S.M., Fornelli, L., Lu, Y., Piech, K.M., Girault, H.H., Tsybin, Y.O.: In-spray supercharging of peptides and proteins in electrospray ionization mass spectrometry. Anal. Chem. 84, 4647-4651 (2012)
101. Alexander, R., Ko, E.C.F., Parker, A.J., Broxton, T.J.: Solvation of ions. XIV. Protic-dipolar aprotic solvent effects on rates of bimolecular reactions. Solvent activity coefficients of reactants and transition states at 25o. J. Am. Chem. Soc. 90, 5049-5069 (1968)
102. Huang, Y., Shi, X., Yu, X., Leymarie, N., Staples, G.O., Yin, H., Killeen, K., Zaia, J.: Improved liquid chromatography-MS/MS of heparan sulfate oligosaccharides via chip-based pulsed makeup flow. Anal. Chem. 83, 8222-8229 (2011)
103. Ganisl, B., Taucher, M., Riml, C., Breuker, K.: Charge as you like! Efficient manipulation of negative ion net charge in electrospray ionization of proteins and nucleic acids. Eur. J. Mass Spectrom. 17, 333-343 (2011)
104. Teo, A.C., Donald, W.A.: Solution additives for supercharging proteins beyond the theoretical maximum proton-transfer limit in electrospray ionization mass spectrometry. Anal. Chem. 85, 4455-4462 (2014)
105. Wawrzynów, A., Chmurzyński, L.: A comparison of acid-base properties of substituted pyridines and their N-Oxides in propylene carbonate. J. Chem. Thermodyn. 30, 713-722 (1998)
106. Schäffner, B., Schäffner, F., Verevkin, S.P., Börner, A.: Organic carbonates as solvents in synthesis and catalysis. Chem. Rev. 110, 4554-4581 (2010)
107. Zikolov, P., Zikolova, T., Budevsky, O.: Acid-base equilibria in ethylene glycol-III. Selection of titration conditions in ethylene glycol medium, protolysis constants of alkaloids in ethylene glycol, and its mixtures. Talanta 23, 587-590 (1976)
108. Hazardous Substance Databank (HSDB) US National Library of Medicine. Available at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB. Accessed 2014
109. JEFFSOL Alkylene Carbonates. Comparative Solvents Data. vol. 1089-0206. Huntsman Corporation: The Woodlands, TX (1999)
110. Konicek, J.: Design and testing of a vaporization calorimeter. enthalpies of vaporization of some alkyl cyanides. Acta Chem. Scand. 27, 1496-1502 (1973)
111. Grimm, R.L., Beauchamp, J.L.: Field-induced droplet ionization mass spectrometry. J. Phys. Chem. B 107, 14161-14163 (2003)
112. Trimpin, S., Inutan, E.D.: Matrix assisted ionization in vacuum, a sensitive and widely applicable ionization method for mass spectrometry. J. Am. Soc. Mass Spectrom. 24, 722-732 (2013)
113. Sweeting, L.M.: Triboluminescence with and without air. Chem. Mater. 13, 854-870 (2001)
114. Williams, E.R., Zhang, R., Rydock, J.: Mixed phase microphysics and cloud electrification. J. Atmos. Sci. 48, 2195-2203 (1991)