Are the electrospray mass spectra of proteins related to their aqueous solution chemistry?

Guevremont, Roger; Siu, Kin Wai Michael; Blanc, J. C. Yves Le; Berman, S. S.

doi:10.1016/1044-0305(92)87005-j

Cited by 131 publications

(68 citation statements)

References 40 publications

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“…Formation of polyanionic species in the negative ion ESI MS usually proceeds via deprotonation of polypeptides. It is the intimate involvement of protons in generating multiply charged ions of biopolymers that led some to believe that the charge state distributions observed in ESI MS must reflect the cumulative charge on the acidic and basic residues in solution [19,20]. In this view, the large-scale conformational dynamics of the polypeptide chains in solution influenced the charge state distributions indirectly, by modulating the pK a values of individual amino acid residues.…”

Section: Can Charge-state Distributions Provide Information On Proteimentioning

confidence: 99%

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Kaltashov

Abzalimov

2008

J. Am. Soc. Mass Spectrom.

155

190

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Multiple charging is an intrinsic feature of electrospray ionization (ESI) of macromolecules. While multiple factors influence the appearance of protein ion charge state distributions in ESI mass spectra, physical dimensions of protein molecules in solution are the major determinants of the extent of multiple charging. This article reviews the information that can be obtained by analyzing ionic charge state distributions in ESI MS, as well as potential pitfalls and limitations of this powerful technique. We also discuss future areas of growth with particular emphasis on applications in structural biology, biotechnology (protein-polymer conjugates), and nanomedicine. (J Am Soc Mass Spectrom 2008, 19, 1239 -1246 [2][3][4] preceded the triumphant entry of this ionization technique into the mainstream of biological mass spectrometry by some time. One particular feature of ESI that seemed to be a major impediment for its application to macromolecules was multiple charging, a phenomenon that seemingly complicated the appearance of mass spectra by crowding them with multiple ion peaks corresponding to the same analyte. Although ionic species carrying more than one elementary charge are not uncommon in mass spectra of macromolecular ions generated by means of fast atom bombardment (FAB) or matrix-assisted laser desorption/ionization (MALDI), they typically account for only a small fraction of the overall signal. Furthermore, typical ionic charge density (defined here as the average number of charges per unit mass) is much lower for the macromolecular ions produced by FAB and MALDI compared with ions generated by ESI. Charge reduction strategies via ion-molecular reactions in the gas phase provided an opportunity to simplify ESI mass spectra of polypeptides by eliminating peaks of multiply charged ions. However, it was the realization that multiple charging is an intrinsic property of ESI process and must be dealt with using mathematical tools, that made it a practical tool for the analysis of macromolecules [5].In retrospect, it seems almost ironic that the multiple charging of macromolecules in ESI MS is now viewed not as a liability, but an extremely valuable asset, which provides a new important dimension to the analysis of biopolymers. Indeed, it was not long after the acceptance of ESI MS as a tool for measuring masses of macromolecular ions that observations were made linking the dramatic changes of ionic charge state distributions to protein denaturation in solution [6,7]. These observations brought about the realization of the potential of ESI MS as a means of probing protein higher order structure and detecting large-scale conformational transitions in solution.Natively folded proteins by definition have stable, compact cores sequestered from the solvent and undergo ESI to produce ions carrying a relatively small number of charges. This is because the compact shape of a tightly folded polypeptide chain in solution does not allow the accommodation of a significant number of protons on their surface upon transit...

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Section: Can Charge-state Distributions Provide Information On Proteimentioning

confidence: 99%

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Kaltashov

Abzalimov

2008

J. Am. Soc. Mass Spectrom.

155

190

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“…It was suggested that the ion abundance profiles in ESI-MS might reflect the abundances of preformed, multiply charged species in aquous solution [24]. Therefore a 'snapshot' of the cytochrome c2 wild-type and mutant conformations could be obtained by observing the CSD in the positive ESI mass spectrum, where the number of charges corresponds to the number of ionized basic residues.…”

Section: Probing Cytochrome C: Conformation Using Csdmentioning

confidence: 99%

Stability study of Rhodobacter capsulatus ferrocytochrome c₂ wild‐type and site‐directed mutants using hydrogen/deuterium exchange monitored by electrospray ionization mass spectrometry

et al. 1996

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“…Dramatic new ionization methods for mass spectrometry (MS) have made possible the formation of protein ions in the gas phase to measure molecular weight and primary sequence information (2-4), even on fmol samples (5,6). Recent studies indicate that protein conformations in solution can affect the resulting charge distribution of the gaseous multiply charged ions formed by electrospray ionization (ESI) (7)(8)(9) and that even noncovalent complexes can survive ESI to form gaseous multiply charged ions (10)(11)(12)(13)(14)(15).…”

mentioning

confidence: 99%

Coexisting stable conformations of gaseous protein ions.

Suckau

Shi

Beu

et al. 1993

Proc. Natl. Acad. Sci. U.S.A.

345

308

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For further insight into the role of solvent in protein conformer stabilization, the structural and dynamic properties of protein ions in vacuo have been probed by hydrogen-deuterium exchange in a Fourier-transform mass spectrometer. Multiply charged ions generated by electrospray ionization of five proteins show exchange reactions with 2H20 at 10-7 torr (1 torr = 133.3 Pa) exhibiting pseudo-first-order kinetics. Gas-phase compactness of the S-S cross-linked RNase A relative to denatured S-derivatized RNase A is indicated by exchange of 35 and 135 hydrogen atoms, respectively. For pure cytochrome c ions, the existence of at least three distinct gaseous conformers is indicated by the substantially different values-52, 113, and 74 -ofreactive H atoms; the observation of these same values for ions of a number-2, 7, and 5, respectively-of different charge states indicates conformational insensitivity to coulombic forces. For each of these conformers, the compactness in vacuo indicated by these values corresponds directly to that of a known conformer structure in the solution from which the conformer ions are produced by electrospray. S-derivatized RNase A ions also exist as at least two gaseous conformers exchanging 50-140 H atoms. Gaseous conformer ions are isomerically stable for hours; removal of solvent greatly increases conformational rigidity. More specific ion-molecule reactions could provide further details of conformer structures.The relationship between the dynamic structure ofproteins in solution and their biological activity has been of longstanding research interest. Protein folding is probably the least well understood step in the sequence of transformations relating genetic information with its expression by protein function (1). Dramatic new ionization methods for mass spectrometry (MS) have made possible the formation of protein ions in the gas phase to measure molecular weight and primary sequence information (2-4), even on fmol samples (5, 6). Recent studies indicate that protein conformations in solution can affect the resulting charge distribution of the gaseous multiply charged ions formed by electrospray ionization (ESI) (7-9) and that even noncovalent complexes can survive ESI to form gaseous multiply charged ions (10)(11)(12)(13)(14)(15).Critical information concerning solvent effects on the conformation and dynamic properties of proteins has come from NMR (16) and from isotope-exchange experiments with 2H20 (17), including those before and during ESI/MS (18,19). With an activation energy of 17-20 kcal/mol (1 cal = 4.184 J) (17), the H/2H exchange rate depends on the pH (17), electrostatic effects (20), proximity of the solvent-accessible surface (21), and conformational flexibility with hydrogen bond cleavage and formation during local unfolding and folding (22). Studies ofgaseous proteins should help delineate the role of solvent in stabilizing protein conformations, but such previous studies have been mainly theoretical (23) because of the lack of experimental approaches. We repor...

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Are the electrospray mass spectra of proteins related to their aqueous solution chemistry?

Cited by 131 publications

References 40 publications

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Stability study of Rhodobacter capsulatus ferrocytochrome c₂ wild‐type and site‐directed mutants using hydrogen/deuterium exchange monitored by electrospray ionization mass spectrometry

Coexisting stable conformations of gaseous protein ions.

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Are the electrospray mass spectra of proteins related to their aqueous solution chemistry?

Cited by 131 publications

References 40 publications

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Do ionic charges in ESI MS provide useful information on macromolecular structure?

Stability study of Rhodobacter capsulatus ferrocytochrome c2 wild‐type and site‐directed mutants using hydrogen/deuterium exchange monitored by electrospray ionization mass spectrometry

Coexisting stable conformations of gaseous protein ions.

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Stability study of Rhodobacter capsulatus ferrocytochrome c₂ wild‐type and site‐directed mutants using hydrogen/deuterium exchange monitored by electrospray ionization mass spectrometry