1
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Guan S, Rabus JM, Maître P, Bythell BJ. Gas-Phase Dissociation Chemistry of Deprotonated RGD. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:55-63. [PMID: 32267154 DOI: 10.1021/jasms.0c00074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We investigate the structure and dissociation pathways of the deprotonated amphoteric peptide arginylglycylasparic acid, [RGD-H]-. We model the pertinent gas-phase structures and fragmentation chemistry of the precursor anions and predominant sequence-informative bond cleavages (b2+H2O, c2, and z1 peaks) and compare these predictions to our tandem mass spectra and infrared spectroscopy experiments. Formation of the b2+H2O anions requires rate-limiting intramolecular back biting to cleave the second amide bond and generate an anhydride structure. Facile cleavage of the newly formed ester bond with concerted expulsion of a cyclic anhydride neutral generates the product structure. IR spectroscopy supports this b2+H2O anion having structures that are essentially identical to C-terminally deprotonated arginylglycine, [RG-H]-. Formation of the c2 anion is predicted to require concerted expulsion of CO2 from the aspartyl side chain carboxylate and cleavage of the N-Calpha bond to produce a proton-bound dimer of arginylglycinamide and acrylate. Proton transfers within the dimer then enable predominant detection of a c2 anion with the negative charge nominally on the central, glycine nitrogen (amidate structure) as the proton affinity of this structure is predicted to be lower than acrylate by ∼27 kJ mol-1. Alternate means of cleaving the same N-Calpha bond produce deprotonated cis-1,4-dibut-2-enoic acid z1 anion structures. These lowest energy processes involve C-H proton mobilization from the aspartyl side chain prior to N-Calpha bond cleavage consistent with proposals from the literature.
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Affiliation(s)
- Shanshan Guan
- Department of Chemistry and Biochemistry, Ohio University, 391 Clippinger Laboratories, Athens, Ohio 45701, United States
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, 1 University Boulevard, St. Louis, Missouri 63121, United States
| | - Jordan M Rabus
- Department of Chemistry and Biochemistry, Ohio University, 391 Clippinger Laboratories, Athens, Ohio 45701, United States
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, 1 University Boulevard, St. Louis, Missouri 63121, United States
| | - Philippe Maître
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, 91405 Orsay, France
| | - Benjamin J Bythell
- Department of Chemistry and Biochemistry, Ohio University, 391 Clippinger Laboratories, Athens, Ohio 45701, United States
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, 1 University Boulevard, St. Louis, Missouri 63121, United States
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2
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Acharya B, Kaushalya WKDN, Martens J, Berden G, Oomens J, Patrick AL. A Combined Infrared Ion Spectroscopy and Computational Chemistry Study of Hydroxyproline Isomers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:1205-1211. [PMID: 32383378 DOI: 10.1021/jasms.0c00061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Hydroxyproline is a common variation of proline, with diverse biological roles. The hydroxylation of proline gives rise to several (natural and/or synthetic) isomeric forms, including both positional isomers and stereoisomers. While mass spectrometry is widely touted as a very selective analytical technique, the identification of closely related isomers often poses a challenge. In these cases, allied technologies become helpful in providing full characterization. Here, infrared multiple photon dissociation (IRMPD) spectroscopy is used to differentiate between three isomers, namely cis-3-hydroxyproline, cis-4-hydroxyproline, and trans-4-hydroxyproline. In contrast to the protonated species which show only minor variations in their IRMPD spectra, lithiated species were found to display significant spectral differences, making their differentiation more straightforward. The conformational origin of these spectral differences was investigated by complementary quantum-chemical calculations.
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Affiliation(s)
- Baku Acharya
- Department of Chemistry, Mississippi State University, Mississippi State, Mississippi, United States
| | - W K D N Kaushalya
- Department of Chemistry, Mississippi State University, Mississippi State, Mississippi, United States
| | - Jonathan Martens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525ED Nijmegen, The Netherlands
| | - Giel Berden
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525ED Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525ED Nijmegen, The Netherlands
| | - Amanda L Patrick
- Department of Chemistry, Mississippi State University, Mississippi State, Mississippi, United States
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3
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Fischer KC, Voss JM, Zhou J, Garand E. Probing Solvation-Induced Structural Changes in Conformationally Flexible Peptides: IR Spectroscopy of Gly3H+·(H2O). J Phys Chem A 2018; 122:8213-8221. [DOI: 10.1021/acs.jpca.8b07546] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kaitlyn C. Fischer
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Ave., Madison, Wisconsin 53706, United States
| | - Jonathan M. Voss
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Ave., Madison, Wisconsin 53706, United States
| | - Jia Zhou
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Ave., Madison, Wisconsin 53706, United States
| | - Etienne Garand
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Ave., Madison, Wisconsin 53706, United States
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4
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Martin-Somer A, Martens J, Grzetic J, Hase WL, Oomens J, Spezia R. Unimolecular Fragmentation of Deprotonated Diproline [Pro2-H]− Studied by Chemical Dynamics Simulations and IRMPD Spectroscopy. J Phys Chem A 2018; 122:2612-2625. [DOI: 10.1021/acs.jpca.7b11873] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Ana Martin-Somer
- Laboratoire Analyse et Modélisation pour la Biologie et l’Environnement, CEA-CNRS, Université Paris Saclay, Evry 91025, France
- Departamento de Química, Facultad de Ciencias, Módulo
13, Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, 28049 Madrid, Spain
| | - Jonathan Martens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands
| | - Josipa Grzetic
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands
| | - William L. Hase
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 908, 1098XH Amsterdam, The Netherlands
| | - Riccardo Spezia
- Laboratoire Analyse et Modélisation pour la Biologie et l’Environnement, CEA-CNRS, Université Paris Saclay, Evry 91025, France
- Laboratoire de Chimie Théorique, LCT, Sorbonne Université, CNRS, F. 75005 Paris, France
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5
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Dunbar RC, Martens J, Berden G, Oomens J. Complexes of Ni(ii) and Cu(ii) with small peptides: deciding whether to deprotonate. Phys Chem Chem Phys 2016; 18:26923-26932. [DOI: 10.1039/c6cp03974j] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Infrared multiple photon dissociation (IRMPD) spectroscopy differentiates two binding modes (iminol versus charge solvated) for Ni(ii) bound to model peptides.
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Affiliation(s)
| | - Jonathan Martens
- FELIX Laboratory
- Institute for Molecules and Materials
- Radboud University
- 6525ED Nijmegen
- The Netherlands
| | - Giel Berden
- FELIX Laboratory
- Institute for Molecules and Materials
- Radboud University
- 6525ED Nijmegen
- The Netherlands
| | - Jos Oomens
- FELIX Laboratory
- Institute for Molecules and Materials
- Radboud University
- 6525ED Nijmegen
- The Netherlands
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6
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Kumar S, Lucas B, Fayeton J, Scuderi D, Alata I, Broquier M, Barbu-Debus KL, Lepère V, Zehnacker A. Photofragmentation mechanisms in protonated chiral cinchona alkaloids. Phys Chem Chem Phys 2016; 18:22668-77. [DOI: 10.1039/c6cp04041a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Photo-fragmentation of protonated alkaloids results in C8–C9 cleavage accompanied or not by hydrogen migration, with a stereochemistry-dependent branching ratio.
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Affiliation(s)
- Sunil Kumar
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Bruno Lucas
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Jacqueline Fayeton
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Debora Scuderi
- Univ. Paris-Sud
- Laboratoire de Chimie Physique
- UMR8000, and CNRS
- Orsay
- France
| | - Ivan Alata
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Michel Broquier
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Katia Le Barbu-Debus
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Valeria Lepère
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
| | - Anne Zehnacker
- Institut des Sciences Moléculaires d'Orsay (ISMO)
- CNRS
- Univ. Paris-Sud
- Université Paris-Saclay
- France
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7
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Marsh BM, Zhou J, Garand E. Vibrational spectroscopy of isolated copper(ii) complexes with deprotonated triglycine and tetraglycine peptides. RSC Adv 2015. [DOI: 10.1039/c4ra09655j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The gas-phase vibrational predissociation spectra of deprotonated copper–triglycine and deprotonated copper–tetraglycine are presented and analyzed.
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Affiliation(s)
- Brett M. Marsh
- Department of Chemistry
- University of Wisconsin
- Madison
- USA
| | - Jia Zhou
- Department of Chemistry
- University of Wisconsin
- Madison
- USA
| | - Etienne Garand
- Department of Chemistry
- University of Wisconsin
- Madison
- USA
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8
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Marsh BM, Duffy EM, Soukup MT, Zhou J, Garand E. Intramolecular Hydrogen Bonding Motifs in Deprotonated Glycine Peptides by Cryogenic Ion Infrared Spectroscopy. J Phys Chem A 2014; 118:3906-12. [DOI: 10.1021/jp501936b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Brett M. Marsh
- Department
of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Erin M. Duffy
- Department
of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Michael T. Soukup
- Department
of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Jia Zhou
- Department
of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Etienne Garand
- Department
of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States
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9
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10
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Scuderi D, Lepere V, Piani G, Bouchet A, Zehnacker-Rentien A. Structural Characterization of the UV-Induced Fragmentation Products in an Ion Trap by Infrared Multiple Photon Dissociation Spectroscopy. J Phys Chem Lett 2014; 5:56-61. [PMID: 26276181 DOI: 10.1021/jz402348n] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Protonated cinchona alkaloids and their dimers undergo photochemical reaction in the gas phase, leading to UV-specific photofragments, not observed by collision-induced dissociation. Simultaneous coupling of UV and IR lasers with a Paul ion trap has been achieved for obtaining the vibrational spectrum of the fragments arising from the photodissociation. The structure of the photoproduced radical has been fully characterized by comparing the experimental spectrum to that simulated by DFT calculations.
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Affiliation(s)
- Debora Scuderi
- †Laboratoire de Chimie Physique and ‡Institut des Sciences Moléculaires d'Orsay, Université Paris-Sud, CNRS, F-91405 Orsay, France
| | - Valeria Lepere
- †Laboratoire de Chimie Physique and ‡Institut des Sciences Moléculaires d'Orsay, Université Paris-Sud, CNRS, F-91405 Orsay, France
| | - Giovanni Piani
- †Laboratoire de Chimie Physique and ‡Institut des Sciences Moléculaires d'Orsay, Université Paris-Sud, CNRS, F-91405 Orsay, France
| | - Aude Bouchet
- †Laboratoire de Chimie Physique and ‡Institut des Sciences Moléculaires d'Orsay, Université Paris-Sud, CNRS, F-91405 Orsay, France
| | - Anne Zehnacker-Rentien
- †Laboratoire de Chimie Physique and ‡Institut des Sciences Moléculaires d'Orsay, Université Paris-Sud, CNRS, F-91405 Orsay, France
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11
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Moore B, Sun Q, Hsu JC, Lee AH, Yoo GC, Ly T, Julian RR. Dissociation chemistry of hydrogen-deficient radical peptide anions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:460-468. [PMID: 22207569 DOI: 10.1007/s13361-011-0318-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 12/05/2011] [Accepted: 12/09/2011] [Indexed: 05/31/2023]
Abstract
The fragmentation chemistry of anionic deprotonated hydrogen-deficient radical peptides is investigated. Homolytic photodissociation of carbon-iodine bonds with 266 nm light is used to generate the radical species, which are subsequently subjected to collisional activation to induce further dissociation. The charges do not play a central role in the fragmentation chemistry; hence deprotonated peptides that fragment via radical directed dissociation do so via mechanisms which have been reported previously for protonated peptides. However, charge polarity does influence the overall fragmentation of the peptide. For example, the absence of mobile protons favors radical directed dissociation for singly deprotonated peptides. Similarly, a favorable dissociation mechanism initiated at the N-terminus is more notable for anionic peptides where the N-terminus is not protonated (which inhibits the mechanism). In addition, collisional activation of the anionic peptides containing carbon-iodine bonds leads to homolytic cleavage and generation of the radical species, which is not observed for protonated peptides presumably due to competition from lower energy dissociation channels. Finally, for multiply deprotonated radical peptides, electron detachment becomes a competitive channel both during the initial photoactivation and following subsequent collisional activation of the radical. Possible mechanisms that might account for this novel collision-induced electron detachment are discussed.
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Affiliation(s)
- Benjamin Moore
- Department of Chemistry, University of California, Riverside, CA 92521, USA
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12
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Grzetic J, Oomens J. Spectroscopic evidence for an oxazolone structure in anionic b-type peptide fragments. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:290-300. [PMID: 22170467 PMCID: PMC3264858 DOI: 10.1007/s13361-011-0297-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 05/31/2023]
Abstract
Infrared spectra of anionic b-type fragments generated by collision induced dissociation (CID) from deprotonated peptides are reported. Spectra of the b(2) fragments of deprotonated AlaAlaAla and AlaTyrAla have been recorded over the 800-1800 cm(-1) spectral range by multiple-photon dissociation (MPD) spectroscopy using an FTICR mass spectrometer in combination with the free electron laser FELIX. Structural characterization of the b-type fragments is accomplished by comparison with density functional theory calculated spectra at the B3LYP/6-31++G(d,p) level for different isomeric structures. Although diketopiperazine structures represent the energetically lowest isomers, the IR spectra suggest an oxazolone structure for the b(2) fragments of both peptides. Deprotonation is shown to occur on the oxazolone α-carbon, which leads to a conjugated structure in which the negative charge is practically delocalized over the entire oxazolone ring, providing enhanced gas-phase stability.
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Affiliation(s)
- Josipa Grzetic
- FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439MN Nieuwegein, The Netherlands
| | - Jos Oomens
- FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439MN Nieuwegein, The Netherlands
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
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13
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Fales BS, Fujamade NO, Oomens J, Rodgers MT. Infrared multiple photon dissociation action spectroscopy and theoretical studies of triethyl phosphate complexes: effects of protonation and sodium cationization on structure. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1862-1871. [PMID: 21952899 DOI: 10.1007/s13361-011-0208-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/29/2011] [Accepted: 07/01/2011] [Indexed: 05/31/2023]
Abstract
The gas-phase structures of protonated and sodium cationized complexes of triethyl phosphate, [TEP + H](+) and [TEP + Na](+), are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer with an electrospray ionization source, and theoretical electronic structure calculations. Measured IRMPD action spectra are compared to linear IR spectra calculated at the B3LYP/6-31 G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral TEP are also performed. Sodium cationization and protonation produce changes in the central phosphate geometry, including an increase in the alkoxy ∠OPO bond angle and shortening of the alkoxy P-O bond. Changes associated with protonation are more pronounced than those produced by sodium cationization.
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Affiliation(s)
- B S Fales
- Department of Chemistry, Wayne State University, Detroit, MI, USA
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14
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Sinha RK, Erlekam U, Bythell BJ, Paizs B, Maître P. Diagnosing the protonation site of b2 peptide fragment ions using IRMPD in the X-H (X = O, N, and C) stretching region. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1645-1650. [PMID: 21953267 DOI: 10.1007/s13361-011-0173-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Revised: 05/17/2011] [Accepted: 05/19/2011] [Indexed: 05/31/2023]
Abstract
Charge-directed fragmentation has been shown to be the prevalent dissociation step for protonated peptides under the low-energy activation (eV) regime. Thus, the determination of the ion structure and, in particular, the characterization of the protonation site(s) of peptides and their fragments is a key approach to substantiate and refine peptide fragmentation mechanisms. Here we report on the characterization of the protonation site of oxazolone b(2) ions formed in collision-induced dissociation (CID) of the doubly protonated tryptic model-peptide YIGSR. In support of earlier work, here we provide complementary IR spectra in the 2800-3800 cm(-1) range acquired on a table-top laser system. Combining this tunable laser with a high power CO(2) laser to improve spectroscopic sensitivity, well resolved bands are observed, with an excellent correspondence to the IR absorption bands of the ring-protonated oxazolone isomer as predicted by quantum chemical calculations. In particular, it is shown that a band at 3445 cm(-1), corresponding to the asymmetric N-H stretch of the (nonprotonated) N-terminal NH(2) group, is a distinct vibrational signature of the ring-protonated oxazolone structure.
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Affiliation(s)
- Rajeev K Sinha
- Laboratoire de Chimie Physique, Université Paris Sud, UMR8000 CNRS, Faculté des Sciences, Bât. 350, 91405, Orsay Cedex, France
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15
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Kamrath MZ, Garand E, Jordan PA, Leavitt CM, Wolk AB, Van Stipdonk MJ, Miller SJ, Johnson MA. Vibrational characterization of simple peptides using cryogenic infrared photodissociation of H2-tagged, mass-selected ions. J Am Chem Soc 2011; 133:6440-8. [PMID: 21449591 PMCID: PMC3099397 DOI: 10.1021/ja200849g] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We present infrared photodissociation spectra of two protonated peptides that are cooled in a ~10 K quadrupole ion trap and "tagged" with weakly bound H(2) molecules. Spectra are recorded over the range of 600-4300 cm(-1) using a table-top laser source, and are shown to result from one-photon absorption events. This arrangement is demonstrated to recover sharp (Δν ~6 cm(-1)) transitions throughout the fingerprint region, despite the very high density of vibrational states in this energy range. The fundamentals associated with all of the signature N-H and C=O stretching bands are completely resolved. To address the site-specificity of the C=O stretches near 1800 cm(-1), we incorporated one (13)C into the tripeptide. The labeling affects only one line in the complex spectrum, indicating that each C=O oscillator contributes a single distinct band, effectively "reporting" its local chemical environment. For both peptides, analysis of the resulting band patterns indicates that only one isomeric form is generated upon cooling the ions initially at room temperature into the H(2) tagging regime.
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Affiliation(s)
- Michael Z. Kamrath
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | - Etienne Garand
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | - Peter A. Jordan
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | - Christopher M. Leavitt
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | - Arron B. Wolk
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | | | - Scott J. Miller
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
| | - Mark A. Johnson
- Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, CT 06520 USA
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