Gas‐phase basicities for ions from bradykinin and its des‐arginine analogues

Ewing, Nigel P.; Pallante, Giovanni A.; Zhang, Xin; Cassady, Carolyn J.

doi:10.1002/jms.188

Cited by 27 publications

(46 citation statements)

References 49 publications

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“…Unfortunately, this break point is not so clear for multiply charged protein ions due to a gradual transition between endergonic and exergonic protonation reaction. Different experimental criteria can be used [15,18,[32][33][34] but the best agreement between experimental and calculated values for the dication 1,7-diaminoheptane was obtained for a deprotonation efficiency of 50% [19]. Previous results obtained in our laboratory confirmed a very good agreement between GB app s measured by the kinetic method and ESSI-MS when an deprotonation efficiency of 50% was used [27].…”

Section: Resultssupporting

confidence: 55%

“…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%

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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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Section: Resultssupporting

confidence: 55%

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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“…+ ions is only~12 kJ mol À1 below that of BK 1 + ions) [23] could, in principle, stabilize a salt-bridge configuration in a fraction of the ion population.…”

Section: -Bradykinin [M+h]mentioning

confidence: 98%

Zwitterionic States in Gas‐Phase Polypeptide Ions Revealed by 157‐nm Ultra‐Violet Photodissociation

Kjeldsen

Silivra

Zubarev

2006

Chemistry A European J

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A new method of detecting the presence of deprotonation and determining its position in gas-phase polypeptide cations is described. The method involves 157-nm ultra-violet photodissociation (UVPD) and is based on monitoring the losses of CO2 (44 Da) from electronically excited deprotonated carboxylic groups relative to competing COOH losses (45 Da) from neutral carboxylic groups. Loss of CO2 is a strong indication of the presence of a zwitterionic [(+)...(-)...(+)] salt bridge in the gas-phase polypeptide cation. This method provides a tool for studying, for example, the nature of binding within polypeptide clusters. Collision-activated dissociation (CAD) of decarboxylated cations localizes the position of deprotonation. Fragment abundances can be used for the semiquantitative assessment of the branching ratio of deprotonation among different acidic sites, however, the mechanism of the fragment formation should be taken into account. Cations of Trp-cage proteins exist preferentially as zwitterions, with the deprotonation position divided between the Asp9 residue and the C terminus in the ratio 3:2. The majority of dications of the same molecule are not zwitterions. Furthermore, 157-nm UVPD produces abundant radical cations M*+ from protonated molecules through the loss of a hydrogen atom. This method of producing M*+ ions is general and can be applied to any gas-phase peptide cation. The abundance of the molecular radical cations M*+ produced is sufficient for further tandem mass spectrometry (MS/MS), which, in the cases studied, yielded side-chain loss of a basic amino acid as the most abundant fragmentation channel together with some backbone cleavages.

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“…221 Ewing et al have proposed an efficiency value of 0.1, approximately 10% of all collisions resulting in a deprotonation reaction, as the 'break point' for peptide ions. 225 With these values, quantitative measurements of Coulomb energy and intrinsic dielectric polarizability in gasphase ions with multiple protons have been demonstrated to provide information about ion conformation in the gas phase. 192 For instance, multiple distinct conformations have been reported for several proteins based on proton transfer kinetics.…”

Section: Reaction (22) Ion-molecule Proton Transfer: Mh + + B → M +mentioning

confidence: 99%

Charge permutation reactions in tandem mass spectrometry

McLuckey

2004

J. Mass Spectrom.

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Central to the tandem mass spectrometry experiment is the process that gives rise to product ions, i.e. the reaction intermediate to stages of mass analysis. Changes in mass or charge of the parent ion (or both) are generally readily detected by all forms of tandem mass spectrometry. Charge changing, or charge permutation, reactions have a long history in mass spectrometry. However, with the advent of new ionization methods, such as electrospray ionization, and the expansion of tandem mass spectrometry instrumentation to include ion trapping instruments, the past decade has seen a major increase in the types of charge permutation reactions that can be studied. Most charge permutation reactions involve electrons or protons as the charge mediating agents. This report, therefore, provides an overview of charge permutation reactions involving protons or electrons. Particular emphasis is placed on processes that involve interactions of precursor ions with gaseous neutral species, electrons or oppositely charged ions. Charge permutation reactions involving electron gain/loss are described first according to a rough order of the energy required for the reaction beginning with the most endoergic reactions and ending with the most exoergic reactions. An analogous approach is then taken with charge permutation reactions involving proton gain/loss. Important charge permutation reactions discussed herein, among others, include those referred to as charge inversion, charge stripping, electron capture dissociation, collision-induced ionization and charge separation. These reaction types, and others described herein, are the subjects of active research and are also finding use in many current areas of application.

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Gas‐phase basicities for ions from bradykinin and its des‐arginine analogues

Cited by 27 publications

References 49 publications

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

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

Zwitterionic States in Gas‐Phase Polypeptide Ions Revealed by 157‐nm Ultra‐Violet Photodissociation

Charge permutation reactions in tandem mass spectrometry

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