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Foley CD, Lee C, Abou Taka A, Au K, Chollet E, Kubasik MA, McCaslin LM, Zwier TS. Site-Specific Photochemistry along a Protonated Peptide Scaffold. J Am Chem Soc 2024; 146:13282-13295. [PMID: 38687970 DOI: 10.1021/jacs.4c01576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
We present a detailed study of the time-dependent photophysics and photochemistry of a known conformation of the two protonated pentapeptides Leu-enkephalin (Tyrosine-Glycine-Glycine-Phenylalanine-Leucine, YGGFL) and its chromophore-swapped analogue FGGYL, carried out under cryo-cooled conditions in the gas phase. Using ultraviolet-infrared (UV-IR) double resonance, we record excited state IR spectra as a function of time delay between UV and IR pulses. We identify unique Tyr OH stretch transitions due to the S1 state and the vibrationally excited triplet state(s) formed by intersystem crossing, Tn(v). Photofragment mass spectra are recorded out of the S1 origin and following UV-IR double resonance. Several competing site-specific fragmentation pathways are discovered involving peptide backbone cleavage, Tyr side chain loss, and N-terminal NH3 loss mediated by electron transfer. In YGGFL, IR excitation in the S1 state promotes electron transfer (ET) from the aromatic ring to the N-terminal R-NH3+ group leading to loss of neutral NH3. This product channel is missing in FGGYL due to the larger distance for ET from Y(4) to NH3+. Selective loss of the Tyr side chain occurs out of an excited state process following UV excitation and is further enhanced by IR excitation in S1 and Tn(v) states of both YGGFL and FGGYL. Finally, IR excitation in the S1 or Tn(v) states fragments the peptide backbone exclusively at amide(4), producing the b4 cation. We postulate that this selective fragmentation results from intersystem crossing to produce vibrationally excited triplets with enough energy to launch the proton along a proton conduit present in the known starting structure.
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Affiliation(s)
- Casey D Foley
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Chin Lee
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Ali Abou Taka
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Kendrew Au
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Etienne Chollet
- Department of Chemistry and Biochemistry, Fairfield University, Fairfield, Connecticut 06824, United States
| | - Matthew A Kubasik
- Department of Chemistry and Biochemistry, Fairfield University, Fairfield, Connecticut 06824, United States
| | - Laura M McCaslin
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Timothy S Zwier
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
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Talbert LE, Julian RR. Methionine and Selenomethionine as Energy Transfer Acceptors for Biomolecular Structure Elucidation in the Gas Phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1601-1608. [PMID: 31222676 PMCID: PMC6697561 DOI: 10.1007/s13361-019-02262-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/31/2019] [Accepted: 06/01/2019] [Indexed: 06/09/2023]
Abstract
Mass spectrometry affords rapid and sensitive analysis of peptides and proteins. Coupling spectroscopy with mass spectrometry allows for the development of new methods to enhance biomolecular structure determination. Herein, we demonstrate two new energy acceptors that can be utilized for action-excitation energy transfer experiments. In the first system, C-S bonds in methionine act as energy acceptors from native chromophores, including tyrosine, tryptophan, and phenylalanine. Comparison among chromophores reveals that tyrosine transfers energy most efficiently at 266 nm, but phenylalanine and tryptophan also transfer energy with comparable efficiencies. Overall, the C-S bond dissociation yields following energy transfer are low for methionine, which led to an investigation of selenomethionine, a common analog that is found in many naturally occurring proteins. Sulfur and selenium are chemically similar, but C-Se bonds are weaker than C-S bonds and have lower lying σ* anti-bonding orbitals. Excitation of peptides containing tyrosine and tryptophan results in efficient energy transfer to selenomethionine and abundant C-Se bond dissociation. A series of helical peptides were examined where the positions of the donor or acceptor were systematically scanned to explore the influence of distance and helix orientation on energy transfer. The distance was found to be the primary factor affecting energy transfer efficiency, suggesting that selenomethionine may be a useful acceptor for probing protein structure in the gas phase.
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Affiliation(s)
- Lance E Talbert
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA
| | - Ryan R Julian
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
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Soorkia S, Jouvet C, Grégoire G. UV Photoinduced Dynamics of Conformer-Resolved Aromatic Peptides. Chem Rev 2019; 120:3296-3327. [DOI: 10.1021/acs.chemrev.9b00316] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Satchin Soorkia
- Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay, France
| | - Christophe Jouvet
- CNRS, Aix Marseille Université, PIIM UMR 7345, 13397, Marseille, France
| | - Gilles Grégoire
- Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, F-91405 Orsay, France
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4
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Talbert LE, Julian RR. Directed-Backbone Dissociation Following Bond-Specific Carbon-Sulfur UVPD at 213 nm. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1760-1767. [PMID: 29623659 PMCID: PMC6087500 DOI: 10.1007/s13361-018-1934-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/16/2018] [Accepted: 02/23/2018] [Indexed: 05/22/2023]
Abstract
Ultraviolet photodissociation or UVPD is an increasingly popular option for tandem-mass spectrometry experiments. UVPD can be carried out at many wavelengths, and it is important to understand how the results will be impacted by this choice. Here, we explore the utility of 213 nm photons for initiating bond-selective fragmentation. It is found that bonds previously determined to be labile at 266 nm, including carbon-iodine and sulfur-sulfur bonds, can also be cleaved with high selectivity at 213 nm. In addition, many carbon-sulfur bonds that are not subject to direct dissociation at 266 nm can be selectively fragmented at 213 nm. This capability can be used to site-specifically create alaninyl radicals that direct backbone dissociation at the radical site, creating diagnostic d-ions. Furthermore, the additional carbon-sulfur bond fragmentation capability leads to signature triplets for fragmentation of disulfide bonds. Absorption of amide bonds can enhance dissociation of nearby labile carbon-sulfur bonds and can be used for stochastic backbone fragmentation typical of UVPD experiments at shorter wavelengths. Several potential applications of the bond-selective fragmentation chemistry observed at 213 nm are discussed. Graphical Abstract ᅟ.
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Affiliation(s)
- Lance E Talbert
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA
| | - Ryan R Julian
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
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Bonner J, Lyon YA, Nellessen C, Julian RR. Photoelectron Transfer Dissociation Reveals Surprising Favorability of Zwitterionic States in Large Gaseous Peptides and Proteins. J Am Chem Soc 2017; 139:10286-10293. [PMID: 28678494 PMCID: PMC5543396 DOI: 10.1021/jacs.7b02428] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Structural
characterization of proteins in the gas phase is becoming
increasingly popular, highlighting the need for a greater understanding
of how proteins behave in the absence of solvent. It is clear that
charged residues exert significant influence over structures in the
gas phase due to strong Coulombic and hydrogen-bonding interactions.
The net charge for a gaseous ion is easily identified by mass spectrometry,
but the presence of zwitterionic pairs or salt bridges has previously
been more difficult to detect. We show that these sites can be revealed
by photoinduced electron transfer dissociation, which produces characteristic
c and z ions only if zwitterionic species are present. Although previous
work on small molecules has shown that zwitterionic pairs are rarely
stable in the gas phase, we now demonstrate that charge-separated
states are favored in larger molecules. Indeed, we have detected zwitterionic
pairs in peptides and proteins where the net charge equals the number
of basic sites, requiring additional protonation at nonbasic residues.
For example, the small protein ubiquitin can sustain a zwitterionic
conformer for all charge states up to 14+, despite having only 13
basic sites. Virtually all of the peptides/proteins examined herein
contain zwitterionic sites if both acidic and basic residues are present
and the overall charge density is low. This bias in favor of charge-separated
states has important consequences for efforts to model gaseous proteins
via computational analysis, which should consider not only charge
state isomers that include salt bridges but also protonation at nonbasic
residues.
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Affiliation(s)
- James Bonner
- Department of Chemistry, University of California , Riverside, California 92521, United States
| | - Yana A Lyon
- Department of Chemistry, University of California , Riverside, California 92521, United States
| | - Christopher Nellessen
- Department of Chemistry, University of California , Riverside, California 92521, United States
| | - Ryan R Julian
- Department of Chemistry, University of California , Riverside, California 92521, United States
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Daly S, Choi CM, Chirot F, MacAleese L, Antoine R, Dugourd P. Action-Self Quenching: Dimer-Induced Fluorescence Quenching of Chromophores as a Probe for Biomolecular Structure. Anal Chem 2017; 89:4604-4610. [DOI: 10.1021/acs.analchem.7b00152] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Steven Daly
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Chang Min Choi
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Fabien Chirot
- Université Lyon, Université Claude Bernard Lyon 1, Ens de Lyon, CNRS, Institut des Sciences Analytiques UMR 5280, 5 rue de la Doua, F-69100, Villeurbanne, France
| | - Luke MacAleese
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Rodolphe Antoine
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Philippe Dugourd
- Université Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
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Bonner JG, Hendricks NG, Julian RR. Structural Effects of Solvation by 18-Crown-6 on Gaseous Peptides and TrpCage after Electrospray Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1661-1669. [PMID: 27506205 DOI: 10.1007/s13361-016-1456-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 06/28/2016] [Accepted: 06/30/2016] [Indexed: 06/06/2023]
Abstract
Significant effort is being employed to utilize the inherent speed and sensitivity of mass spectrometry for rapid structural determination of proteins; however, a thorough understanding of factors influencing the transition from solution to gas phase is critical for correct interpretation of the results from such experiments. It was previously shown that combined use of action excitation energy transfer (EET) and simulated annealing can reveal detailed structural information about gaseous peptide ions. Herein, we utilize this method to study microsolvation of charged groups by retention of 18-crown-6 (18C6) in the gas phase. In the case of GTP (CEGNVRVSRE LAGHTGY), solvation of the 2+ charge state leads to reduced EET, whereas the opposite result is obtained for the 3+ ion. For the mini-protein C-Trpcage, solvation by 18C6 leads to dramatic increase in EET for the 3+ ion. Examination of structural details probed by molecular dynamics calculations illustrate that solvation by 18C6 alleviates the tendency of charged side chains to seek intramolecular solvation, potentially preserving native-like structures in the gas phase. These results suggest that microsolvation may be an important tool for facilitating examination of native-like protein structures in gas phase experiments. Graphical Abstract ᅟ.
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Affiliation(s)
- James G Bonner
- Department of Chemistry, University of California, Riverside, CA, 92521, USA
| | - Nathan G Hendricks
- Department of Chemistry, University of California, Riverside, CA, 92521, USA
| | - Ryan R Julian
- Department of Chemistry, University of California, Riverside, CA, 92521, USA.
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Hendricks NG, Julian RR. Leveraging ultraviolet photodissociation and spectroscopy to investigate peptide and protein three-dimensional structure with mass spectrometry. Analyst 2016; 141:4534-40. [DOI: 10.1039/c6an01020b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recent advances in mass spectrometry and lasers have facilitated the development of novel experiments combining the benefits of both technologies.
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Affiliation(s)
| | - Ryan R. Julian
- Department of Chemistry
- University of California
- Riverside
- USA
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9
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Czar MF, Jockusch RA. Sensitive probes of protein structure and dynamics in well-controlled environments: combining mass spectrometry with fluorescence spectroscopy. Curr Opin Struct Biol 2015; 34:123-34. [DOI: 10.1016/j.sbi.2015.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 09/24/2015] [Accepted: 09/28/2015] [Indexed: 10/25/2022]
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Hendricks NG, Julian RR. Two-step energy transfer enables use of phenylalanine in action-EET for distance constraint determination in gaseous biomolecules. Chem Commun (Camb) 2015; 51:12720-3. [DOI: 10.1039/c5cc03779d] [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]
Abstract
Two-step energy transfer is observed between phenylalanine, tyrosine, and modified cysteine. This gas-phase system enables use of phenylalanine in energy transfer experiments, provides specific distance information for structure determination, and is easily examined with mass spectrometry.
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Affiliation(s)
| | - Ryan R. Julian
- Department of Chemistry
- University of California, Riverside
- Riverside
- USA
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