2012
DOI: 10.1007/s13361-012-0384-0
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Conformational Distribution of Bradykinin [bk + 2 H]2+ Revealed by Cold Ion Spectroscopy Coupled with FAIMS

Abstract: We employ cold ion spectroscopy (CIS) in conjunction with high-field asymmetric waveform ion mobility spectrometry (FAIMS) to study the peptide bradykinin in its doubly protonated charge state ([bk+2 H] 2+ ). Using FAIMS, we partially separate the electrosprayed [bk+2 H] 2+ ions into two conformational families and selectively introduce one of them at a time into a cold ion trap mass spectrometer, where we probe them by UV photofragment spectroscopy. Although the two conformational families have distinct ele… Show more

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Cited by 61 publications
(72 citation statements)
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“…The trans-Pro species readily isomerizes to cis-Pro when it is energized by collisions; however, under the room temperature conditions of our drift tube, it is still energetically accessible and remains a small portion of the annealed distribution. A similar observation has been made for a variety of other peptidic systems [18,31] and suggests that the relative conformer populations we measure after annealing reflect the Boltzmann weights of these states at a given temperature. The exact temperature to which the relative populations correspond is not obvious; however, it may reflect that of the drift tube (300 K), but it may also reflect a higher temperature, depending on the rate of cooling in the drift tube and the height of the barriers separating the conformers.…”
Section: The Case For Quasi-equilibrium and Kinetic Trapping From Solsupporting
confidence: 80%
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“…The trans-Pro species readily isomerizes to cis-Pro when it is energized by collisions; however, under the room temperature conditions of our drift tube, it is still energetically accessible and remains a small portion of the annealed distribution. A similar observation has been made for a variety of other peptidic systems [18,31] and suggests that the relative conformer populations we measure after annealing reflect the Boltzmann weights of these states at a given temperature. The exact temperature to which the relative populations correspond is not obvious; however, it may reflect that of the drift tube (300 K), but it may also reflect a higher temperature, depending on the rate of cooling in the drift tube and the height of the barriers separating the conformers.…”
Section: The Case For Quasi-equilibrium and Kinetic Trapping From Solsupporting
confidence: 80%
“…Mass spectrometry and ion mobility would be supplemented by additional structural information, while spectroscopy would be simplified by the presence of mass and conformational filters. Analogous experiments have been developed using UV photofragmentation [30,31], but infrared spectroscopy has the advantage of providing vibrational information that can be compared directly with theoretical calculations.…”
mentioning
confidence: 99%
“…Although these bands originate from higher energy states of the molecule, they are different from what we normally consider hot bands because the molecule has a different equilibrium geometry and there is a barrier on the potential energy surface separating the conformers. In principle, one could attempt to anneal the molecule by heating and re-cooling to transfer the trapped population into the lowest energy conformation -such annealing has been done both in ion mobility experiments [9,23] and in spectroscopic experiments [24]. However, it may be that these trapped conformations are the most interesting to interrogate.…”
Section: Necessity Of Cooling For Large Moleculesmentioning
confidence: 99%
“…One possibility to help deal with this problem is to separate different conformations of the ions physically before injecting them into an ion trap, and one approach to doing this is to combine ion mobility with cold ion spectroscopy. In our laboratory we have recently combined Field Asymmetric Ion Mobility Spectrometry (FAIMS) with a cold, 22-pole ion trap to perform conformer pre-selection prior to ion trapping and UV photofragment spectroscopy [24,142]. Since conformer overlap is a major Returning to where much of the impetus for buffer-gas cooling of ions began, Dieter Gerlich, in collaboration with the Roithova group in Prague, has recently developed a new wire-based quadrupole ion trap, which they inserted into a commercial tandem mass spectrometer (Fig.…”
Section: Some Specific Implementations Of the Above Techniquesmentioning
confidence: 99%
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