Deprotonation reactions of multiply protonated ubiquitin ions

Cassady, Carolyn J.; Wronka, John; Kruppa, Gary; Laukien, Frank H.; Hettich, Robert L.

doi:10.1002/rcm.1290080511

Cited by 80 publications

(78 citation statements)

References 37 publications

(4 reference statements)

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“…The ion/molecule reaction data were taken from the research of Cassady et al (Cassady et al, 1994). The ion/molecule reaction results were originally reported as rate constants, but were converted here to rates by multiplying the rate constants by 6.48 ϫ 10 9 cm Ϫ3 , the highest number density of the neutral base reported to be used in the ion cyclotron resonance mass spectrometry studies.…”

Section: Ion/ion Reactions Of Multiply Charged Ions ▪mentioning

confidence: 99%

Ion/ion chemistry of high-mass multiply charged ions

McLuckey

Stephenson

1998

Mass Spectrom. Rev.

226

189

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Electrospray ionization has enabled the establishment of a new area of ion chemistry research based on the study of the reactions of high-mass multiply charged ions with ions of opposite polarity. The multiple-charging phenomenon associated with electrospray makes possible the generation of multiply charged reactant ionsthat yield charged products as a result of partial neutralization due to ion/ion chemistry. The charged products can be readily studied with mass spectrometric methods, providing useful insights into reaction mechanisms. This review presents the research done in this area, all of which has been performed within the past decade.

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Section: Ion/ion Reactions Of Multiply Charged Ions ▪mentioning

confidence: 99%

Ion/ion chemistry of high-mass multiply charged ions

McLuckey

Stephenson

1998

Mass Spectrom. Rev.

226

189

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“…Due to the poor ionization efficiency with nondenaturing buffer and low ion transmission of the quadrupole in the high mass range, mostly qualitative data were obtained for denatured proteins. A few years later, the groups of Cassady [13][14][15] and Williams [2,4] used ESI-FT-ICR mass spectrometers to precisely determine the GB app s of multiply charged proteins by the bracketing method. A defined protein charge state is preselected and allowed to react with volatile base in the ICR cell.…”

mentioning

confidence: 99%

“…The kinetics of the deprotonation is then studied by recording the signal intensities of different charge states of a protein with different volatile bases. The rate constant of the deprotonation reaction was found to increase with increasing charge state of the ion and with increasing basicity of the amine [13]. Nevertheless, most of the experimental data dealt only with proteins sprayed from denaturing solution.…”

mentioning

confidence: 99%

Investigation of deprotonation reactions on globular and denatured proteins at atmospheric pressure by ESSI-MS

Touboul

Jecklin

Zenobi

2008

J. Am. Soc. Mass Spectrom.

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Deprotonation reactions of multiply charged protein ions have been studied by introducing volatile reference bases at atmospheric pressure between an electrosonic spray ionization (ESSI) source and the inlet of a mass spectrometer. Apparent gas-phase basicities (GB app ) of different charge states of protein ions were determined by a bracketing approach. The results pp obtained depend on the conformation of the protein ions in the gas phase, which is linked to the type of buffer used (denaturing or nondenaturing [1] rapidly became established as the method of choice for the production of large biomolecular ions in the gas phase. For proteins, ESI leads to the formation of multiply charged ions, both in the positive and negative ion modes. The charge-state distribution is directly related to the conformation of the macromolecular ions [2] and the proton transfer reactions in the gas phase [3]. Thermodynamic information, such as values for the gas-phase acidity/basicity (GA/GB), is essential to the understanding of the proton transfer processes and generation of ions by ESI in general. The intrinsic gas-phase basicity of a [M ϩ (n Ϫ 1)H] (n Ϫ 1)ϩ ion or the gas-phase acidity of a [M ϩ nH] nϩ ion can be defined as the free enthalpy change ⌬G 0 of the reaction:Since this reaction proceeds with a reverse activation barrier, due to Coulombic repulsion between the two charges product ions, the terms "apparent gas-phase acidity" (GA app ) and "apparent gas-phase basicity" (GB app ) are more appropriate. The GA app is defined as the sum of the ⌬G and the energy of the activation barrier, considered as a negative term [4].Determination of GB app s of peptides and proteins provides important information which is analogous to measurements of pKa in solution. For example, pKa values are greatly affected by intramolecular interactions, and the conversion of the denatured to the native form maximizes these interactions. Similarly, GB app values will also reflect the conformation of the ions in the gas phase.For more than 10 years, research groups have tried to determine apparent gas-phase basicities of peptides and proteins. For small peptides, like bradykinin and its des-arginine analogues, the kinetic method can be directly used to determine GB app values [5,6]. The energy of the activation barrier was obtained by measuring the kinetic energy release to calculate the intrinsic GB of two different charge states. Unfortunately, this method is quite difficult to transfer to multiply charged protein ions.A bracketing technique, consisting of evaluating the qualitative or quantitative rate of proton transfer between a neutral volatile base and protein ions was introduced to measure GB app values of multiply charges ions [4,7,8]. In terms of instrumentation, different systems can be used to observe the deprotonation reactions. High-pressure mass spectrometry (HPMS) experiments were designed by the group of Kebarle to study cluster formation from small organic or inorganic ions, and water in particular [9,10]. This apparatus was...

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“…Ubiquitin was also examined and is of interest because many folded states have been previously observed and studied via inter alia ion-molecule deprotonation [76] and time-resolved electrospray mass spectrometry experiments [77]. In our previous work with neutral pH solutions [43], the leak-in of weak acids resulted in a modest increase in q ave (+7.8 and +7.3 for acetic and formic acids, respectively) relative to the nano-ESI mass spectrum of a neutral pH solution (q ave =+6.8), whereas the leak-in of the strong acids TFA and HCl resulted in a distribution corresponding to the folded ubiquitin A-State or even a folding back to a more native state (N-state) with an observed CSD from +4 to +8 (q ave =+5.9) [61].…”

Section: Cytochrome C and Ubiquitin: Positive Polaritymentioning

confidence: 99%

Vapor Treatment of Electrospray Droplets: Evidence for the Folding of Initially Denatured Proteins on the Sub-Millisecond Time-Scale

Kharlamova

DeMuth

McLuckey

2011

J. Am. Soc. Mass Spectrom.

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The exposure of electrospray droplets generated from either highly acidic or highly basic solutions to basic or acidic vapors, respectively, admitted into the counter-current drying gas, has been shown to lead to significant changes in the observed charge state distributions of proteins. In both cases, distributions of charge states changed from relatively high charge states, indicative of largely denatured proteins, to lower charge state distributions that are more consistent with native protein conformations. Ubiquitin, cytochrome c, myoglobin, and carbonic anhydrase were used as model systems. In some cases, bimodal distributions were observed that are not noted under any solution pH conditions. The extent to which changes in charge state distributions occur depends upon the initial solution pH and the pK a or pK b of the acidic or basic reagent, respectively. The evolution of charged droplets in the sampling region of the mass spectrometer inlet aperture, where the vapor exposure takes place, occurs within roughly 1 ms. The observed changes in the spectra, therefore, are a function of the magnitude of the pH change as well as the rates at which the proteins can respond to this change. The exposure of electrospray droplets in this fashion may provide means for accessing transient folding states for further characterization by mass spectrometry.

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Deprotonation reactions of multiply protonated ubiquitin ions

Cited by 80 publications

References 37 publications

Ion/ion chemistry of high-mass multiply charged ions

Ion/ion chemistry of high-mass multiply charged ions

Investigation of deprotonation reactions on globular and denatured proteins at atmospheric pressure by ESSI-MS

Vapor Treatment of Electrospray Droplets: Evidence for the Folding of Initially Denatured Proteins on the Sub-Millisecond Time-Scale

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