Supercharging with <i>m</i>-Nitrobenzyl Alcohol and Propylene Carbonate: Forming Highly Charged Ions with Extended, Near-Linear Conformations

Going, Catherine C.; Williams, Evan R.

doi:10.1021/acs.analchem.5b00071

Cited by 43 publications

(67 citation statements)

References 93 publications

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“…The gradual increase in size of ions with charge > 8+ is an indicator for an unzipping of the already elongated, presumably helical conformations to even more extended structures [9,21]. In fact, earlier IM-MS studies showed that ions in even higher charge states than the ones investigated here slowly approach the size of the linear form L with a CCS of ~2600 Å 2 [7,9] -the upper size limit for ubiquitin ions. However, IM-MS methods only yield information about the overall size and shape of protein ions, while further structural details, such as the secondary structure, remain elusive.…”

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 59%

“…The theoretical CCS of the folded, native structure (N) and that of the partially unfolded and mostly helical A state (A) found in denaturing solutions are indicated as dashed, vertical lines in Figure 2a, together with the CCS values of two hypothetical structures, an extended, 5 fully α-helical (H) and a fully linear conformation (L) [7]. The gradual increase in size of ions with charge > 8+ is an indicator for an unzipping of the already elongated, presumably helical conformations to even more extended structures [9,21]. In fact, earlier IM-MS studies showed that ions in even higher charge states than the ones investigated here slowly approach the size of the linear form L with a CCS of ~2600 Å 2 [7,9] -the upper size limit for ubiquitin ions.…”

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 98%

“…Highly charged species were generated from a solution containing 1% of formic acid. To increase the number of charges even further, the supercharging reagent propylene carbonate (PC) was added to the solutions at a concentration of v/v 15% [9].…”

Section: Materials and Sample Preparationmentioning

confidence: 99%

“…Ions with up to 13 charges (which equals the number of the apparent basic sites Lys, Arg, His, and the N-terminus) were observed from denaturing solutions containing water/methanol and 1% of formic acid. In order to increase the number of charges on the gas-phase protein ions well above the number of basic sites in the sequence, the supercharging reagent propylene carbonate (PC) was used [9].…”

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 99%

“…The different structures that ubiquitin ions can adopt in the gas phase have been investigated previously using ion mobility-mass spectrometry (IM-MS) and related techniques [7,9,20,21]. Such experiments typically yield arrival time distributions (ATDs) from which the overall size of the ions by means of an angular-averaged collision crosssection (CCS) can be deduced.…”

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 99%

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From Compact to String—The Role of Secondary and Tertiary Structure in Charge-Induced Unzipping of Gas-Phase Proteins

Warnke

Hoffmann

Seo

et al. 2016

J. Am. Soc. Mass Spectrom.

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In the gas phase, protein ions can adopt a broad range of structures, which have been investigated extensively in the past using ion mobility-mass spectrometry (IM-MS) based methods. Compact ions with low number of charges undergo a Coulomb-driven transition to partially folded species when the charge increases and finally form extended structures with presumably little or no defined structure when the charge state is high. However, with respect to the secondary structure, IM-MS methods are essentially blind. Infrared (IR) spectroscopy, on the other hand, is sensitive to such structural details and there is increasing evidence that helices as well as β-sheet-like structures can exist in the gas phase, especially for ions in low charge states. Very recently, we showed that also the fully extended form of highly charged protein ions can adopt a distinct type of secondary structure that features a characteristic C5-type hydrogen bond pattern. Here we use a combination of IM-MS and IR spectroscopy to further investigate the influence of the initial, native conformation on the formation of these structures. Our results indicate that when intramolecular Coulomb-repulsion is large enough to overcome the stabilization energies of the genuine secondary structure, all proteins, regardless of their sequence or native conformation, form C5-type hydrogen bond structures. Furthermore, our results suggest that in highly charged proteins the positioning of charges along the sequence is only marginally influenced by the basicity of individual residues.In the gas-phase environment of a mass spectrometer, proteins can adopt a broad range of distinct structures. When electrosprayed from native, buffered solutions especially large proteins and protein complexes are known to retain features of their condensed-phase conformation -a fact that found broad application in the field of native mass spec-

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Section: Ubiquitin -From Compact To Stringmentioning

confidence: 59%

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 98%

Section: Materials and Sample Preparationmentioning

confidence: 99%

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 99%

Section: Ubiquitin -From Compact To Stringmentioning

confidence: 99%

See 3 more Smart Citations

From Compact to String—The Role of Secondary and Tertiary Structure in Charge-Induced Unzipping of Gas-Phase Proteins

Warnke

Hoffmann

Seo

et al. 2016

J. Am. Soc. Mass Spectrom.

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Ladungsinduziertes Entwinden isolierter Proteine zu einer definierten Sekundärstruktur

et al. 2016

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Highly Charged Protein Ions: The Strongest Organic Acids to Date

et al. 2017

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The basicity of highly protonated cytochrome c (cyt c) and myoglobin (myo) ions were investigated using tandem mass spectrometry,i on-molecule reactions (IMRs), and theoretical calculations as af unction of charge state. Surprisingly,h ighly charged protein ions (HCPI) can readily protonate non-polar molecules and inert gases,i ncluding Ar, O 2 ,a nd N 2 in thermal IMRs.T he most HCPIs that can be observed are over 130 kJ mol À1 less basic than the least basic neutral organic molecules known( tetrafluoromethane and methane). Based on theoretical calculations,itispredicted that protonated cyt ca nd myo ions should spontaneously lose ap roton to vacuum for charge states in which every third residue is protonated. In this study,H CPIs are formed where every fourth residue on average is protonated. These results indicate that protein ions in higher charge states can be formed using al ow-pressure ion source to reduce proton-transfer reactions between protein ions and gases from the atmosphere.Electrospray ionization (ESI) is renowned for its ability to form intact, gaseous,m ultiply charged protein ions for rapid and sensitive detection by mass spectrometry. [1] However,the mechanism by which protein ions are formed in ESI is controversial and continues to be actively debated. Thet wo primary competing models to explain ion formation are known as the charge residue model (CRM) [2] and the ion evaporation model (IEM). [3] In both models,a sn eutral molecules evaporate from ac harged droplet, the electric field at the surface of the droplet increases,w hich initiates fission. [4] Such droplet fission events result in the emission of afine stream of smaller droplets that remove less than 1% of the mass but more than 30 %o ft he charge of the precursor droplet. [4,5] In the CRM, sequential droplet evaporation and Coulombic fission events yield acharged droplet that contains asingle analyte ion, which evaporates to dryness via the loss of neutral solvent molecules.Inthe IEM, the electric field on the surface of ah ighly charged droplet near the moment of ion formation is sufficient to result in the ejection of an analyte ion from the surface of the ionic droplet. Themajority of current evidence indicates that fully desolvated protein ions formed from buffered aqueous solutions are formed by the CRM. Charge carriers such as solvated hydronium ions can be lost via ion evaporation during the ESI process. [6] Recently,the chain-ejection model (CEM), [7] which is related to the IEM, was proposed to explain the formation of protein ions from denaturing solutions based on results from molecular dynamics simulations. [7] In the CEM, ad enatured, disordered protein chain is ejected from ah ighly charged, nanometer-sized ionic droplet. As the protein ion protrudes and is ejected from the droplet, proton transfer to the protein ion can occur. However,t he mechanism by which highly charged protein ions (HCPIs) are formed from denaturing solutions is less well established with evidence supporting both the CRM [8] and CEM/IEM having be...

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Supercharging with m-Nitrobenzyl Alcohol and Propylene Carbonate: Forming Highly Charged Ions with Extended, Near-Linear Conformations

Cited by 43 publications

References 93 publications

From Compact to String—The Role of Secondary and Tertiary Structure in Charge-Induced Unzipping of Gas-Phase Proteins

From Compact to String—The Role of Secondary and Tertiary Structure in Charge-Induced Unzipping of Gas-Phase Proteins

Ladungsinduziertes Entwinden isolierter Proteine zu einer definierten Sekundärstruktur

Highly Charged Protein Ions: The Strongest Organic Acids to Date

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