1
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Beckett D, El-Baba TJ, Zhang Z, Clemmer DE, Raghavachari K. Tautomerization of H +KPGG: Entropic Consequences of Strong Hydrogen-Bond Networks in Peptides. J Phys Chem A 2023; 127:6282-6291. [PMID: 37490716 PMCID: PMC10405267 DOI: 10.1021/acs.jpca.3c03744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/11/2023] [Indexed: 07/27/2023]
Abstract
Ion mobility spectrometry-mass spectrometry and quantum chemical calculations are used to determine the structures and stabilities of the singly protonated peptide H+KPGG. The two peaks making up the IMS distribution are shown to be tautomers differing by the location of the extra proton on either the lysine side chain or the N-terminus. The lysine-protonated tautomer is strongly preferred entropically while being disfavored in terms of the electronic energy and enthalpy. This relationship is shown, through comparison of all low-lying conformers of both tautomers, to be related to the strong hydrogen-bond network of the N-terminally protonated tautomer. A general relationship is demonstrated wherein stronger cross-peptide hydrogen-bond networks result in entropically disfavored conformers. Further effects of the H+KPGG hydrogen-bond network are probed by computationally examining singly and doubly methylated analogues. These results demonstrate the importance of the entropic consequences of hydrogen bonds to peptide stability as well as techniques for perturbing the hydrogen-bond network and folding preferences of peptides via minimal chemical modification.
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Affiliation(s)
- Daniel Beckett
- Department
of Chemistry, Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Tarick J. El-Baba
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Zhichao Zhang
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - David E. Clemmer
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Krishnan Raghavachari
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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2
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Nacsa AB, Kígyósi M, Czakó G. Protonation of serine: conformers, proton affinities and gas-phase basicities at the "gold standard" and beyond. Phys Chem Chem Phys 2023; 25:8891-8902. [PMID: 36916632 DOI: 10.1039/d3cp00612c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The potential energy surfaces (PESs) of serine and its protonated counterparts are investigated to determine the structures of the minima. A total of 95 neutral serine, 15 N-(amino-) and 46 O-(carbonyl-)protonated serine conformers are found. Their relative energies, geometries and harmonic vibrational frequencies are determined at the MP2/aug-cc-pVDZ level of theory. To obtain highly accurate thermodynamic values, further computations are performed: the ten conformers with the lowest relative energies from each molecule type (neutral, N- and O-protonated) are further optimized using the explicitly correlated CCSD(T)-F12a/cc-pVDZ-F12 method (for neutral serine, harmonic vibrational frequencies were also computed). In addition, auxiliary corrections were determined: basis-set effects up to CCSD(T)-F12b/cc-pVQZ-F12, electron correlation effects up to CCSDT(Q), core correlation and second-order Douglas-Kroll relativistic effects along with zero-point energy contributions. Two important thermodynamic parameters (at 298.15 K), proton affinity (PA)/gas-phase basicity (GB) are calculated considering the two different protonation sites: 218.05 ± 0.2/209.86 ± 0.6 kcal mol-1 and 205.87 ± 0.2/196.36 ± 0.3 kcal mol-1 for the amino and carbonyl sites, respectively. The uncertainty of the determined values was approximated based on various sources including auxiliary corrections, basis-set effects, harmonic vibrational frequencies.
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Affiliation(s)
- András B Nacsa
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Máté Kígyósi
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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3
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Nacsa AB, Czakó G. Benchmark Ab Initio Determination of the Conformers, Proton Affinities, and Gas-Phase Basicities of Cysteine. J Phys Chem A 2022; 126:9667-9679. [PMID: 36524999 PMCID: PMC9806835 DOI: 10.1021/acs.jpca.2c07035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A systematic conformational mapping combined with literature data leads to 85 stable neutral cysteine conformers. The implementation of the same mapping process for the protonated counterparts reveals 21 N-(amino-), 64 O-(carbonyl-), and 37 S-(thiol-)protonated cysteine conformers. Their relative energies and harmonic vibrational frequencies are given at the MP2/aug-cc-pVDZ level of theory. Further benchmark ab initio computations are performed for the 10 lowest-lying neutral and protonated amino acid conformers (for each type) such as CCSD(T)-F12a/cc-pVDZ-F12 geometry optimizations (and frequency computations for cysteine) as well as auxiliary correction computations of the basis set effects up to CCSD(T)-F12b/cc-pVQZ-F12, electron correlation effects up to CCSDT(Q), core correlation effects, second-order Douglass-Kroll relativistic effects, and zero-point energy contributions. Boltzmann-averaged 0 (298.15) K proton affinity and [298.15 K gas-phase basicity] values of cysteine are predicted to be 214.96 (216.39) [208.21], 201.83 (203.55) [194.16], and 193.31 (194.74) [186.40] kcal/mol for N-, O-, and S-protonation, respectively, also considering the previously described auxiliary corrections.
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4
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Utility of Atmospheric-Pressure Chemical Ionization and Photoionization Mass Spectrometry in Bottom-Up Proteomics. SEPARATIONS 2022. [DOI: 10.3390/separations9020042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In a typical bottom-up proteomics workflow, proteins are enzymatically cleaved, and the resulting peptides are analyzed by HPLC with electrospray ionization (ESI) tandem mass spectrometry. This approach is practical and widely applied. It has, however, limitations mostly related to less efficient or even inefficient ionization of some peptides in ESI sources. Gas-phase ionization methods like atmospheric-pressure chemical ionization (APCI) or atmospheric-pressure photoionization (APPI) offer alternative ways of detecting various analytes. This work is a systematic study of the ionization efficiencies of peptides in ESI, APCI, and APPI and the applicability of the mentioned ionizations in proteomics. A set of peptide standards and bovine serum albumin digests were examined using a high-resolution mass spectrometer coupled to an ultra HPLC system. Since the ionization efficiency in APCI and APPI depends strongly on experimental conditions, the ion source settings and mobile phase compositions were optimized for each ionization technique. As expected, tryptic peptides were best detected using ESI. The numbers of chymotrypsin peptides successfully detected by ESI, APPI, and APCI were comparable. In the case of Glu-C digest, APPI detected the highest number of peptides. The results suggest that gas-phase ionization techniques, particularly APPI, are an interesting alternative for detecting peptides and delivering complementary data in proteomics.
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5
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Dékány AÁ, Czakó G. Benchmark ab initio proton affinity and gas-phase basicity of α-alanine based on coupled-cluster theory and statistical mechanics. J Comput Chem 2022; 43:19-28. [PMID: 34676890 DOI: 10.1002/jcc.26767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/16/2021] [Accepted: 09/27/2021] [Indexed: 11/06/2022]
Abstract
We determine the proton affinity (PA) and gas-phase basicity (GB) of amino acid α-alanine at a chemically accurate level by performing explicitly-correlated CCSD(T)-F12b/aug-cc-pVDZ geometry optimizations and normal mode vibrational frequency calculations as well as CCSD(T)-F12b/aug-cc-pVTZ energy computations at the possible neutral and protonated geometries. Temperature effects at 298.15 K considering translational, rotational, and vibrational enthalpy and entropy corrections are obtained via standard statistical mechanics utilizing the molecular geometries and the harmonic vibrational energy levels. Both the amino nitrogen (N) and the carbonyl oxygen (O) atoms are proven to be potential protonation sites and a systematic conformational search reveals 3 N- and 9 O-protonated conformers in the 0.00-7.88 and 25.43-30.43 kcal/mol energy ranges at 0 K, respectively. The final computed PA and GB values at (0)298.15 K in case of N-protonation are (214.47)216.80 and 207.07 kcal/mol, respectively, whereas the corresponding values for O-protonation are (189.04)190.63 and 182.31 kcal/mol. The results of the benchmark high-level coupled-cluster computations are utilized to assess the accuracy of several lower-level cost-effective methods such as MP2 and density functional theory with various functionals (SOGGA11-X, M06-2X, PBE0, B3LYP, M06, TPSS).
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Affiliation(s)
- Attila Á Dékány
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Szeged, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Szeged, Hungary
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6
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Andersson Å, Poline M, Houthuijs KJ, van Outersterp RE, Berden G, Oomens J, Zhaunerchyk V. IRMPD Spectroscopy of Homo- and Heterochiral Asparagine Proton-Bound Dimers in the Gas Phase. J Phys Chem A 2021; 125:7449-7456. [PMID: 34428065 PMCID: PMC8419839 DOI: 10.1021/acs.jpca.1c05667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 08/11/2021] [Indexed: 12/16/2022]
Abstract
We investigate gas-phase structures of homo- and heterochiral asparagine proton-bound dimers with infrared multiphoton dissociation (IRMPD) spectroscopy and quantum-chemical calculations. Their IRMPD spectra are recorded at room temperature in the range of 500-1875 and 3000-3600 cm-1. Both varieties of asparagine dimers are found to be charge-solvated based on their IRMPD spectra. The location of the principal intramolecular H-bond is discussed in light of harmonic frequency analyses using the B3LYP functional with GD3BJ empirical dispersion. Contrary to theoretical analyses, the two spectra are very similar.
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Affiliation(s)
- Åke Andersson
- Department
of Physics, University of Gothenburg, 41296 Gothenburg, Sweden
| | - Mathias Poline
- Department
of Physics, Stockholm University, 10691 Stockholm, Sweden
| | - Kas J. Houthuijs
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Rianne E. van Outersterp
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Giel Berden
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- FELIX
Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Vitali Zhaunerchyk
- Department
of Physics, University of Gothenburg, 41296 Gothenburg, Sweden
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7
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Abstract
A systematic conformational search reveals three N- (amino) and eight O- (carbonyl) protonated glycine conformers with benchmark equilibrium(adiabatic) relative energies in the 0.00-7.51(0.00-7.37) and 25.91-31.61(24.45-30.28) kcal mol-1 ranges, respectively. Benchmark ab initio structures of the glycine conformers and its protonated species are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory and the relative energy computations consider basis-set effects up to aug-cc-pVQZ with CCSD(T)-F12b, electron correlation up to CCSDT(Q), core correlation corrections, scalar relativistic effects, and zero-point energy contributions. The best predictions for Boltzmann-averaged 0(298.15) K proton affinities and [298.15 K gas-phase basicities] of glycine are 211.00(212.43)[204.75] and 186.38(187.64)[180.21] kcal mol-1 for N- and O-protonation, respectively, in excellent agreement with experiments.
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Affiliation(s)
- András B Nacsa
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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8
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Montilla M, Luis JM, Salvador P. Origin-Independent Decomposition of the Static Polarizability. J Chem Theory Comput 2021; 17:1098-1105. [PMID: 33439029 DOI: 10.1021/acs.jctc.0c00926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Real-space analysis tools afford additive and transferable contributions of atoms to molecular properties. In the case of the molecular (hyper)polarizabilities, the atomic contributions that have been derived so far include a charge-transfer term that is origin-dependent. In this letter, we present the first genuinely origin-independent energy-based (OIEB) methodology for the decomposition of the static (hyper)polarizabilities that benefits from real-space molecular energy decomposition schemes, focusing on the static polarizability and showing that extension to static hyperpolarizabilities is straightforward. The numerical realization of the OIEB method shows the expected origin independence, atomic additivity, and transferability of atomic and functional group polarizability tensors. Furthermore, the OIEB atomic (fragment) polarizability tensors are symmetric by definition.
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Affiliation(s)
- Marc Montilla
- Institute of Computational Chemistry and Catalysis, Chemistry Department, University of Girona, Montilivi Campus, Girona, Catalonia 17003, Spain
| | - Josep M Luis
- Institute of Computational Chemistry and Catalysis, Chemistry Department, University of Girona, Montilivi Campus, Girona, Catalonia 17003, Spain
| | - Pedro Salvador
- Institute of Computational Chemistry and Catalysis, Chemistry Department, University of Girona, Montilivi Campus, Girona, Catalonia 17003, Spain
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9
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Chiavarino B, Sinha RK, Crestoni ME, Corinti D, Filippi A, Fraschetti C, Scuderi D, Maitre P, Fornarini S. Binding Motifs in the Naked Complexes of Target Amino Acids with an Excerpt of Antitumor Active Biomolecule: An Ion Vibrational Spectroscopy Assay. Chemistry 2021; 27:2348-2360. [PMID: 33175428 DOI: 10.1002/chem.202003555] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/30/2020] [Indexed: 11/06/2022]
Abstract
The structures of proton-bound complexes of 5,7-dimethoxy-4H-chromen-4-one (1) and basic amino acids (AAs), namely, histidine (His) and lysine (Lys), have been examined by means of mass spectrometry coupled with IR ion spectroscopy and quantum chemical calculations. This selection of systems is based on the fact that 1 represents a portion of glabrescione B, a natural small molecule of promising antitumor activity, while His and Lys are protein residues lining the cavity of the alleged receptor binding site. These species are thus a model of the bioactive adduct, although clearly the isolated state of the present study bears little resemblance to the complex biological environment. A common feature of [1+AA+H]+ complexes is the presence of a protonated AA bound to neutral 1, in spite of the fact that the gas-phase basicity of 1 is comparable to those of Lys and His. The carbonyl group of 1 acts as a powerful hydrogen-bond acceptor. Within [1+AA+H]+ the side-chain substituents (imidazole group for His and terminal amino group for Lys) present comparable basic properties to those of the α-amino group, taking part to a cooperative hydrogen-bond network. Structural assignment, relying on the comparative analysis of the infrared multiple photon dissociation (IRMPD) spectrum and calculated IR spectra for the candidate geometries, derives from an examination over two frequency ranges: 900-1800 and 2900-3700 cm-1 . Information gained from the latter one proved especially valuable, for example, pointing to the contribution of species characterized by an unperturbed carboxylic OH or imidazole NH stretching mode.
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Affiliation(s)
- Barbara Chiavarino
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
| | - Rajeev K Sinha
- Department of Atomic and Molecular Physics, Manipal University, Manipal, 576104, Karnataka, India
| | - Maria Elisa Crestoni
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
| | - Davide Corinti
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
| | - Antonello Filippi
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
| | - Caterina Fraschetti
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
| | - Debora Scuderi
- Institut de Chimie Physique, UMR8000, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Philippe Maitre
- Institut de Chimie Physique, UMR8000, CNRS, Université Paris-Saclay, 91405, Orsay, France
| | - Simonetta Fornarini
- Dipartimento di Chimica e Tecnologie del Farmaco, Università degli studi di Roma La Sapienza, P.le A. Moro 5, 00185, Roma, Italy
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10
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Maitre P, Scuderi D, Corinti D, Chiavarino B, Crestoni ME, Fornarini S. Applications of Infrared Multiple Photon Dissociation (IRMPD) to the Detection of Posttranslational Modifications. Chem Rev 2019; 120:3261-3295. [PMID: 31809038 DOI: 10.1021/acs.chemrev.9b00395] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Infrared multiple photon dissociation (IRMPD) spectroscopy allows for the derivation of the vibrational fingerprint of molecular ions under tandem mass spectrometry (MS/MS) conditions. It provides insight into the nature and localization of posttranslational modifications (PTMs) affecting single amino acids and peptides. IRMPD spectroscopy, which takes advantage of the high sensitivity and resolution of MS/MS, relies on a wavelength specific fragmentation process occurring on resonance with an IR active vibrational mode of the sampled species and is well suited to reveal the presence of a PTM and its impact in the molecular environment. IRMPD spectroscopy is clearly not a proteomics tool. It is rather a valuable source of information for fixed wavelength IRMPD exploited in dissociation protocols of peptides and proteins. Indeed, from the large variety of model PTM containing amino acids and peptides which have been characterized by IRMPD spectroscopy, specific signatures of PTMs such as phosphorylation or sulfonation can be derived. High throughput workflows relying on the selective fragmentation of modified peptides within a complex mixture have thus been proposed. Sequential fragmentations can be observed upon IR activation, which do not only give rise to rich fragmentation patterns but also overcome low mass cutoff limitations in ion trap mass analyzers. Laser-based vibrational spectroscopy of mass-selected ions holding various PTMs is an increasingly expanding field both in the variety of chemical issues coped with and in the technological advancements and implementations.
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Affiliation(s)
- Philippe Maitre
- Laboratoire de Chimie Physique (UMR8000), Université Paris-Sud, CNRS, Université Paris Saclay, 91405, Orsay, France
| | - Debora Scuderi
- Laboratoire de Chimie Physique (UMR8000), Université Paris-Sud, CNRS, Université Paris Saclay, 91405, Orsay, France
| | - Davide Corinti
- Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma "La Sapienza", I-00185 Roma, Italy
| | - Barbara Chiavarino
- Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma "La Sapienza", I-00185 Roma, Italy
| | - Maria Elisa Crestoni
- Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma "La Sapienza", I-00185 Roma, Italy
| | - Simonetta Fornarini
- Dipartimento di Chimica e Tecnologie del Farmaco, Università di Roma "La Sapienza", I-00185 Roma, Italy
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11
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The any particle molecular orbital/molecular mechanics approach. J Mol Model 2019; 25:316. [PMID: 31529219 DOI: 10.1007/s00894-019-4153-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/14/2019] [Indexed: 10/26/2022]
Abstract
A computational scheme is proposed to broaden the range of applications of multicomponent methodologies for the study of local properties of big molecular systems existing in the gas phase and in solvated environments. This scheme extends the any particle molecular orbital (APMO) approach in the quantum mechanics/molecular mechanics (QM/MM) framework. As a first assessment of the performance of the proposed approach, we estimate the proton affinities (PAs) of seventy amines in the gas phase and the proton binding energies (PBEs) in the gas phase and in an explicitly solvated environment of the sixty-one protons present in the chignolin protein. These calculations are performed with the QM/MM versions of the APMO second-order proton propagator (APMO-PP2) and the APMO extended Koopmans' theorem (APMO-KT) approaches. Calculated PAs and PBEs show significant reductions in the computational effort with a reduced loss in accuracy. These results suggest that the APMO/MM scheme might be used as a low-cost multi-component alternative for studies of local properties in big molecular systems. Graphical Abstract QMMM regions and CPU times for the APMO/MM approach.
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12
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Shin J. Extended kinetic method study of the effect of
ortho
‐,
meta
‐, and
para
‐chlorination on the proton affinity of phenylalanine with full entropy analysis. J PHYS ORG CHEM 2019. [DOI: 10.1002/poc.3966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Joong‐Won Shin
- Division of Science, Mathematics, and TechnologyGovernors State University University Park IL USA
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13
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Bailey LS, Alves M, Galy N, Patrick AL, Polfer NC. Mechanistic insights into intramolecular phosphate group transfer during collision induced dissociation of phosphopeptides. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:449-458. [PMID: 30860300 DOI: 10.1002/jms.4351] [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: 12/20/2018] [Revised: 02/22/2019] [Accepted: 03/04/2019] [Indexed: 05/28/2023]
Abstract
We report on the rearrangement chemistry of model phosphorylated peptides during collision-induced dissociation (CID), where intramolecular phosphate group transfers are observed from donor to acceptor residues. Such "scrambling" could result in inaccurate modification localization, potentially leading to misidentifications. Systematic studies presented herein provide mechanistic insights for the unusually high phosphate group rearrangements presented some time ago by Reid and coworkers (Proteomics 2013, 13 [6], 964-973). It is postulated here that a basic residue like histidine can play a key role in mediating the phosphate group transfer by deprotonating the serine acceptor site. The proposed mechanism is consistent with the observation that fast collisional activation by collision-cell CID and higher-energy collisional dissociation (HCD) can shut down rearrangement chemistry. Additionally, the rearrangement chemistry is highly dependent on the charge state of the peptide, mirroring previous studies that less rearrangement is observed under mobile proton conditions.
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Affiliation(s)
- Laura S Bailey
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Mélanie Alves
- Département de chimie, UFR 926, Sorbonne Université, Paris, France
| | - Nicolas Galy
- Département de chimie, Université Paul Sabatier, Toulouse, France
| | - Amanda L Patrick
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
| | - Nicolas C Polfer
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
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14
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Javanshad R, Honarvar E, Venter AR. Addition of Serine Enhances Protein Analysis by DESI-MS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:694-703. [PMID: 30771107 DOI: 10.1007/s13361-018-02129-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/21/2018] [Accepted: 12/27/2018] [Indexed: 05/18/2023]
Abstract
Previous studies have suggested that the loss in sensitivity of DESI-MS for large molecules such as proteins is due to the poor dissolution during the short time scale of desorption and ionization. An investigation into the effect of serine as a solvent additive leads to the interesting observation that there is a concentration-dependent improvement in protein signal intensity when micromolar to low millimolar concentrations of serine is combined with a suitable co-additive in DESI spray. This effect, however, was not observed during similar ESI-MS experiments, where the same solvents and proteins were sprayed directly into the MS inlet. This suggests that the mechanism of signal improvement in DESI is associated with the desorption step of proteins, possibly by facilitating dissolution or improving solubility of proteins on the surface in the solvent micro-layer formed during DESI. Other than poor dissolution, cation adduction such as by sodium ions is also a major contributing factor to the mass-dependent loss in sensitivity in both ESI and DESI, leading to an increase in limits of detection for larger proteins. The adduction becomes a more pressing issue in native-state studies of proteins, as lower charge states are more susceptible to adduction. Previous studies have shown that addition of amino acids to the working spray solution during ESI-MS reduces sodium adduction and can help in stabilization of native-state proteins. Similar to the observed reduction in sodium adducts during native-state ESI-MS, when serine is added to the desorbing spray in DESI-MS, the removal of up to 10 mM NaCl is shown. A selection of proteins with high and low pI and molecular weights was analyzed to investigate the effects of serine on signal intensity by improvements in protein solubility and adduct removal. Graphical Abstract.
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Affiliation(s)
- Roshan Javanshad
- Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA
| | - Elahe Honarvar
- Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA
| | - Andre R Venter
- Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA.
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15
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Huo D, Qin T, Zu L. Energetic switch of the proline effect in collision-induced dissociation of singly and doubly protonated peptide Ala-Ala-Arg-Pro-Ala-Ala. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:55-65. [PMID: 30426600 DOI: 10.1002/jms.4311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 10/30/2018] [Accepted: 11/06/2018] [Indexed: 06/09/2023]
Abstract
Suppression of the selective cleavage at N-terminal of proline is observed in the peptide cleavage by proteolytic enzyme trypsin and in the fragment ion mass spectra of peptides containing Arg-Pro sequence. An insight into the fragmentation mechanism of the influence of arginine residue on the proline effect can help in prediction of mass spectra and in protein structure analysis. In this work, collision-induced dissociation spectra of singly and doubly charged peptide AARPAA were studied by ESI MS/MS and theoretical calculation methods. The proline effect was evaluated by comparing the experimental ratio of fragments originated from cleavage of different amide bonds. The results revealed that the backbone amide bond cleavage was selected by the energy barrier height of the fragmentation pathway although the strong proton affinity of the Arg side chain affected the stereostructure of the peptide and the dissociation mechanism. The thermodynamic stability of the fragment ions played a secondary role in the abundance ratio of fragments generated via different pathways. Fragmentation studies of protonated peptide AACitPAA supported the energy-dependent hypothesis. The results provide an explanation to the long-term arguments between the steric conflict and the proton mobility mechanisms of proline effect.
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Affiliation(s)
- Dayujia Huo
- College of Chemistry, Beijing Normal University, Beijing, China
| | - Tai Qin
- College of Chemistry, Beijing Normal University, Beijing, China
| | - Lily Zu
- College of Chemistry, Beijing Normal University, Beijing, China
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16
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Affiliation(s)
- Oleg V. Boyarkin
- Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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17
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Stegeby H. Overview of antiproton affinities for functional groups relevant in particle-beam cancer therapy. Cancer Rep (Hoboken) 2018. [DOI: 10.1002/cnr2.1128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Henrik Stegeby
- Department of Chemistry-Ångström, The Theoretical Chemistry Programme; Uppsala University; Uppsala Sweden
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18
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Smith ZM, Steinmetz V, Martens J, Oomens J, Poutsma JC. Infrared Multiple Photon Dissociation Spectroscopy of Cationized Canavanine: Side-Chain Substitution Influences Gas-Phase Zwitterion Formation †. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2018; 429:158-173. [PMID: 29962900 PMCID: PMC6020040 DOI: 10.1016/j.ijms.2017.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Infrared multiple photon dissociation spectroscopy was performed on protonated and cationized canavanine (Cav), a non-protein amino acid oxy-analog of arginine. Infrared spectra in the XH stretching region (3000 - 4000 cm-1) were obtained at the Centre Laser Infrarouge d'Orsay (CLIO) facility. Comparison of the experimental infrared spectra with scaled harmonic frequencies at the B3LYP/6-31+G(d,p) level of theory indicates that canavanine is in a canonical neutral form in CavH+, CavLi+, and CavNa+; therefore, these cations are charge-solvated structures. The infrared spectrum of CavK+ is consistent with a mixture of Cav in canonical and zwitterionic forms leading to both charge-solvated and salt-bridged cationic structures. The Cav moiety in CavCs+ is shown to be zwitterionic, forming a salt-bridged structure for the cation. Infrared spectra in the fingerprint region (1000 - 2000 cm-1) obtained at the FELIX Laboratory in Nijmegen, Netherlands support these assignments. These results show that that a single oxygen atom substitution in the side chain reduces the stability of the zwitterion compared to that of the protein amino acid arginine (Arg), which has been shown previously to adopt a zwitterionic structure in ArgNa+ and ArgK+. This difference can be explained in part due to the decreased basicity of Cav (PA = 1001 kJ/mol) as compared to arginine (PA = 1051 kJ/mol), but not entirely, as lysine, which has nearly the same proton affinity as Cav, (~993 kJ/mol) forms only canonical structures with Na+, K+, and Cs+. A major difference between the zwitterionic forms of ArgM+ and CavM+ is that the protonation site is on the side chain for Arg and on the N-terminus for Cav. This results in systematically weaker salt bridges in the Cav zwitterions. In addition, the presence of another hydrogen-bonding acceptor atom in the side chain contributes to the stability of the canonical structures for the smaller alkali cations.
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Affiliation(s)
- Zachary M Smith
- Department of Chemistry, The College of William and Mary, Williamsburg, VA 23187-8795
| | - Vincent Steinmetz
- Laboratoire de Chimie Physique, CNRS UMR 8000, Université Paris Sud, Université Paris Saclay, CNRS, Orsay France
| | - Jonathan Martens
- Radboud University, Institute for Molecules and Materials FELIX Laboratory, Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials FELIX Laboratory, Nijmegen, The Netherlands
- Van't Hoff Institute for Molecular Sciences University of Amsterdam, Amsterdam, The Netherlands
| | - John C Poutsma
- Department of Chemistry, The College of William and Mary, Williamsburg, VA 23187-8795
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19
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Brahim B, Tabet JC, Alves S. Positive and negative ion mode comparison for the determination of DNA/peptide noncovalent binding sites through the formation of "three-body" noncovalent fragment ions. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2018; 24:168-177. [PMID: 29232990 DOI: 10.1177/1469066717735672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Gas-phase fragmentation of single strand DNA-peptide noncovalent complexes is investigated in positive and negative electrospray ionization modes.Collision-induced dissociation experiments, performed on the positively charged noncovalent complex precursor ions, have confirmed the trend previously observed in negative ion mode, i.e. a high stability of noncovalent complexes containing very basic peptidic residues (i.e. R > K) and acidic nucleotide units (i.e. Thy units), certainly incoming from the existence of salt bridge interactions. Independent of the ion polarity, stable noncovalent complex precursor ions were found to dissociate preferentially through covalent bond cleavages of the partners without disrupting noncovalent interactions. The resulting DNA fragment ions were found to be still noncovalently linked to the peptides. Additionally, the losses of an internal nucleic fragment producing "three-body" noncovalent fragment ions were also observed in both ion polarities, demonstrating the spectacular salt bridge interaction stability. The identical fragmentation patterns (regardless of the relative fragment ion abundances) observed in both polarities have shown a common location of salt bridge interaction certainly preserved from solution. Nonetheless, most abundant noncovalent fragment ions (and particularly three-body ones) are observed from positively charged noncovalent complexes. Therefore, we assume that, independent of the preexisting salt bridge interaction and zwitterion structures, multiple covalent bond cleavages from single-stranded DNA/peptide complexes rely on an excess of positive charges in both electrospray ionization ion polarities.
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Affiliation(s)
- Bessem Brahim
- Sorbonne Universités - UPMC Paris 06, Institut Parisien de Chimie Moléculaire (IPCM) University, Paris, France
| | - Jean-Claude Tabet
- Sorbonne Universités - UPMC Paris 06, Institut Parisien de Chimie Moléculaire (IPCM) University, Paris, France
| | - Sandra Alves
- Sorbonne Universités - UPMC Paris 06, Institut Parisien de Chimie Moléculaire (IPCM) University, Paris, France
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20
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Nomura S, Tsuchida H, Kajiwara A, Yoshida S, Majima T, Saito M. Dissociation of biomolecules in liquid environments during fast heavy-ion irradiation. J Chem Phys 2017; 147:225103. [PMID: 29246061 DOI: 10.1063/1.5009367] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The effect of aqueous environment on fast heavy-ion radiation damage of biomolecules was studied by comparative experiments using liquid- and gas-phase amino acid targets. Three types of amino acids with different chemical structures were used: glycine, proline, and hydroxyproline. Ion-induced reaction products were analyzed by time-of-flight secondary-ion mass spectrometry. The results showed that fragments from the amino acids resulting from the C-Cα bond cleavage were the major products for both types of targets. For liquid-phase targets, specific products originating from chemical reactions in solutions were observed. Interestingly, multiple dissociated atomic fragments were negligible for the liquid-phase targets. We found that the ratio of multifragment to total fragment ion yields was approximately half of that for gas-phase targets. This finding agreed with the results of other studies on biomolecular cluster targets. It is concluded that the suppression of molecular multifragmentation is caused by the energy dispersion to numerous water molecules surrounding the biomolecular solutes.
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Affiliation(s)
- Shinji Nomura
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Hidetsugu Tsuchida
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Akihiro Kajiwara
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Shintaro Yoshida
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Takuya Majima
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
| | - Manabu Saito
- Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
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Pedraza-González L, Charry J, Quintero W, Alí-Torres J, Reyes A. Fast and accurate prediction of proton affinities: revisiting the extended Koopmans' theorem for protons. Phys Chem Chem Phys 2017; 19:25324-25333. [PMID: 28890980 DOI: 10.1039/c7cp04936f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work we propose schemes based on the extended Koopmans' theorem for quantum nuclei (eKT), in the framework of the any particle molecular orbital approach (APMO/KT), for the quantitative prediction of gas phase proton affinities (PAs). The performance of these schemes has been tested on a set of 300 organic molecules containing diverse functional groups. The APMO/KT scheme scaled by functional group (APMO/KT-SC-FG) displays an overall mean absolute error of 1.1 kcal mol-1 with respect to experimental data. Its performance in PA calculations is similar to that of post-Hartree-Fock composite methods or that of the APMO second order proton propagator (APMO/PP2) approach. The APMO/KT-SC-FG scheme is also employed to predict PAs of polyfunctional molecules such as the Nerve Agent VX and the 20 common α-amino acids, finding excellent agreement with available theoretical and/or experimental data. The accuracy of the predictions demonstrates that the APMO/KT-SC-FG scheme is a low-cost alternative to adiabatic methods for the calculation of accurate PAs. One of the most appealing features of the APMO/KT-SC-FG scheme, is that PAs can be derived from one single-point APMO Hartree-Fock calculation.
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Affiliation(s)
- Laura Pedraza-González
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 # 45-03, Bogotá, Colombia.
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22
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Mu X, Song T, Siu CK, Chu IK. Tautomerization and Dissociation of Molecular Peptide Radical Cations. CHEM REC 2017. [DOI: 10.1002/tcr.201700013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Xiaoyan Mu
- Department of Chemistry; University of Hong Kong; Pokfulam, Hong Kong SAR P. R. China
| | - Tao Song
- Department of Chemistry; University of Hong Kong; Pokfulam, Hong Kong SAR P. R. China
| | - Chi-Kit Siu
- Department of Biology and Chemistry; City University of Hong Kong; 83 Tat Chee Avenue Kowloon Tong, Hong Kong SAR P. R. China
| | - Ivan K. Chu
- Department of Chemistry; University of Hong Kong; Pokfulam, Hong Kong SAR P. R. China
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23
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Raczyńska ED, Gal JF, Maria PC. Enhanced Basicity of Push-Pull Nitrogen Bases in the Gas Phase. Chem Rev 2016; 116:13454-13511. [PMID: 27739663 DOI: 10.1021/acs.chemrev.6b00224] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitrogen bases containing one or more pushing amino-group(s) directly linked to a pulling cyano, imino, or phosphoimino group, as well as those in which the pushing and pulling moieties are separated by a conjugated spacer (C═X)n, where X is CH or N, display an exceptionally strong basicity. The n-π conjugation between the pushing and pulling groups in such systems lowers the basicity of the pushing amino-group(s) and increases the basicity of the pulling cyano, imino, or phosphoimino group. In the gas phase, most of the so-called push-pull nitrogen bases exhibit a very high basicity. This paper presents an analysis of the exceptional gas-phase basicity, mostly in terms of experimental data, in relation with structure and conjugation of various subfamilies of push-pull nitrogen bases: nitriles, azoles, azines, amidines, guanidines, vinamidines, biguanides, and phosphazenes. The strong basicity of biomolecules containing a push-pull nitrogen substructure, such as bioamines, amino acids, and peptides containing push-pull side chains, nucleobases, and their nucleosides and nucleotides, is also analyzed. Progress and perspectives of experimental determinations of GBs and PAs of highly basic compounds, termed as "superbases", are presented and benchmarked on the basis of theoretical calculations on existing or hypothetical molecules.
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Affiliation(s)
- Ewa D Raczyńska
- Department of Chemistry, Warsaw University of Life Sciences (SGGW) , ul. Nowoursynowska 159c, 02-776 Warszawa, Poland
| | - Jean-François Gal
- Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France
| | - Pierre-Charles Maria
- Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France
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24
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Noble JE, De Santis E, Ravi J, Lamarre B, Castelletto V, Mantell J, Ray S, Ryadnov MG. A De Novo Virus-Like Topology for Synthetic Virions. J Am Chem Soc 2016; 138:12202-10. [PMID: 27585246 DOI: 10.1021/jacs.6b05751] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A de novo topology of virus-like assembly is reported. The design is a trifaceted coiled-coil peptide helix, which self-assembles into ultrasmall, monodisperse, anionic virus-like shells that encapsulate and transfer both RNA and DNA into human cells. Unlike existing artificial systems, these shells share the same physical characteristics of viruses being anionic, nonaggregating, abundant, hollow, and uniform in size, while effectively mediating gene silencing and transgene expression. These are the smallest virus-like structures reported to date, both synthetic and native, with the ability to adapt and transfer small and large nucleic acids. The design thus offers a promising solution for engineering bespoke artificial viruses with desired functions.
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Affiliation(s)
- James E Noble
- National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom
| | - Emiliana De Santis
- National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom
| | - Jascindra Ravi
- National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom
| | - Baptiste Lamarre
- National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom
| | - Valeria Castelletto
- Department of Chemistry, University of Reading , Reading RG6 6AD, United Kingdom
| | - Judith Mantell
- Wolfson Bio-imaging Facility, Department of Biochemistry, University of Bristol , Bristol BS8 1TD, United Kingdom
| | - Santanu Ray
- SET, University of Brighton , Brighton BN2 4GJ, United Kingdom
| | - Maxim G Ryadnov
- National Physical Laboratory , Hampton Road, Teddington TW11 0LW, United Kingdom
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25
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Calculated bond dissociation energies and enthalpy of formation of α-amino acid radicals. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-1975-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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26
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Feng R, Yin H, Kong X. Structure of protonated tryptophan dimer in the gas phase investigated by IRPD spectroscopy and theoretical calculations. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30 Suppl 1:24-28. [PMID: 27539410 DOI: 10.1002/rcm.7615] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
RATIONAL In addition to proton affinity (PA), side chains may also have an effect on the structures of amino acid complex ions in the gas phase. A previous study showed that the most stable isomer of Pro2 H(+) favored a salt-bridged structure. Tryptophan has a PA close to that of proline, but a quite different side chain. Thus, it will be interesting to discover whether the salt-bridged or charge-solvated conformation is energetically more favorable for Trp2 H(+) in the gas phase. METHODS The infrared photodissociation (IRPD) spectrum of Trp2 H(+) was obtained using a Fourier transform ion cyclotron resonance mass spectrometer equipped with a tunable OPO laser. The non-covalent cluster ions were generated by electrospray ionization. Structural optimization and frequency calculation of the selected isomers were performed at the M062X/6-311++G(d,p) level. RESULTS The experimental IRPD spectrum of Trp2 H(+) was reported in the region of 2700-3750 cm(-1) . Theoretical calculations show that the most stable isomer has a charge-solvated structure. Its energy was found to be 9 kcal/mol lower than that of the most stable salt-bridged isomer. The experimental spectrum is consistent with the predicted spectra of the most stable charge-solvated structures. Temperature effect on the stability of isomers was also evaluated and it was revealed that the contribution from salt-bridged isomers can be neglected at a temperature of 300 K. CONCLUSIONS Combining the method of IRPD spectroscopy with theoretical calculations, the structures of Trp2 H(+) were investigated. It is shown that the structures of Trp2 H(+) are dominated by charge-solvated forms. The results also indicate that the side chain may considerably affect the stability of the zwitterionic forms. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Ruxia Feng
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, China
| | - Hong Yin
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, China
| | - Xianglei Kong
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, China
- Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, 300071, China
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27
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Akashi S, Downard KM. Effect of charge on the conformation of highly basic peptides including the tail regions of histone proteins by ion mobility mass spectrometry. Anal Bioanal Chem 2016; 408:6637-48. [DOI: 10.1007/s00216-016-9777-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 06/28/2016] [Accepted: 07/06/2016] [Indexed: 10/21/2022]
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28
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Hadadi N, Ataman M, Hatzimanikatis V, Panayiotou C. Molecular thermodynamics of metabolism: quantum thermochemical calculations for key metabolites. Phys Chem Chem Phys 2016; 17:10438-53. [PMID: 25799954 DOI: 10.1039/c4cp05825a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The present work is the first of a series of papers aiming at a coherent and unified development of the thermodynamics of metabolism and the rationalization of feasibility analysis of metabolic pathways. The focus in this part is on high-level quantum chemical calculations of the thermochemical quantities of relatively heavy metabolites such as amino acids/oligopeptides, nucleosides, saccharides and their derivatives in the ideal gas state. The results of this study will be combined with the corresponding hydration/solvation results in subsequent parts of this work in order to derive the desired thermochemical quantities in aqueous solutions. The above metabolites exist in a vast conformational/isomerization space including rotational conformers, tautomers or anomers exhibiting often multiple or cooperative intramolecular hydrogen bonding. We examine the challenges posed by these features for the reliable estimation of thermochemical quantities. We discuss conformer search, conformer distribution and averaging processes. We further consider neutral metabolites as well as protonated and deprotonated metabolites. In addition to the traditional presentation of gas-phase acidities, basicities and proton affinities, we also examine heats and free energies of ionic species. We obtain simple linear relations between the thermochemical quantities of ions and the formation quantities of their neutral counterparts. Furthermore, we compare our calculations with reliable experimental measurements and predictive calculations from the literature, when available. Finally, we discuss the next steps and perspectives for this work.
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Affiliation(s)
- N Hadadi
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland
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29
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Mirzaei S, Khalilian MH, Taherpour AA. Mechanistic study of the hydrolytic degradation and protonation of temozolomide. RSC Adv 2015. [DOI: 10.1039/c5ra04680g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Two pathways for the degradation of the anticancer agent, temozolomide, were investigated, in which the most energy-favoured mechanism was a combination of the two possible pathways.
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Affiliation(s)
| | | | - Avat Arman Taherpour
- Faculty of Chemistry
- Razi University
- Kermanshah
- Iran
- Medical Biology Research Center
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30
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Govender KK, Naidoo KJ. Evaluating AM1/d-CB1 for Chemical Glycobiology QM/MM Simulations. J Chem Theory Comput 2014; 10:4708-17. [DOI: 10.1021/ct500373p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Krishna K. Govender
- Scientific Computing
Research Unit and Department
of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Kevin J. Naidoo
- Scientific Computing
Research Unit and Department
of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
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31
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Liu F, Lu W, Fang Y, Liu J. Evolution of oxidation dynamics of histidine: non-reactivity in the gas phase, peroxides in hydrated clusters, and pH dependence in solution. Phys Chem Chem Phys 2014; 16:22179-91. [PMID: 25213401 DOI: 10.1039/c4cp03550j] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxidation of histidine by (1)O2 is an important process associated with oxidative damage to proteins during aging, diseases and photodynamic therapy of tumors and jaundice, and photochemical transformations of biological species in the troposphere. However, the oxidation mechanisms and products of histidine differ dramatically in these related environments which range from the gas phase through aerosols to aqueous solution. Herein we report a parallel gas- and solution-phase study on the (1)O2 oxidation of histidine, aimed at evaluating the evolution of histidine oxidation pathways in different media and at different ionization states. We first investigated the oxidation of protonated and deprotonated histidine ions and the same systems hydrated with explicit water molecules in the gas phase, using guided-ion-beam-scattering mass spectrometry. Reaction coordinates and potential energy surfaces for these systems were established on the basis of density functional theory calculations, Rice-Ramsperger-Kassel-Marcus modeling and direct dynamics simulations. Subsequently we tracked the oxidation process of histidine in aqueous solution under different pH conditions, using on-line UV-Vis spectroscopy and electrospray mass spectrometry monitoring systems. The results show that two different routes contribute to the oxidation of histidine depending on its ionization states. In each mechanism hydration is essential to suppressing the otherwise predominant dissociation of reaction intermediates back to reactants. The oxidation of deprotonated histidine in the gas phase involves the formation of 2,4-endoperoxide and 2-hydroperoxide of imidazole. These intermediates evolve to hydrated imidazolone in solution, and the latter either undergoes ring-closure to 6α-hydoxy-2-oxo-octahydro-pyrrolo[2,3-d]imidazole-5-carboxylate or cross-links with another histidine to form a dimeric product. In contrast, the oxidation of protonated histidine is mediated by 2,5-endoperoxide and 5-hydroperoxide, which convert to stable hydrated imidazolone end-product in solution. The contrasting mechanisms and reaction efficiencies of protonated vs. deprotonated histidine, which lead to pH dependence in the photooxidation of histidine, are interpreted in terms of the chemistry of imidazole with (1)O2. The biological implications of the results are also discussed.
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Affiliation(s)
- Fangwei Liu
- Department of Chemistry and Biochemistry, Queens College and the Graduate Center of the City University of New York, 65-30 Kissena Blvd., Queens, New York 11367, USA.
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Conformational analysis of glutamic acid: a density functional approach using implicit continuum solvent model. J Mol Model 2014; 20:2396. [PMID: 25135067 DOI: 10.1007/s00894-014-2396-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 07/23/2014] [Indexed: 10/24/2022]
Abstract
Amino acids are constituents of proteins and enzymes which take part almost in all metabolic reactions. Glutamic acid, with an ability to form a negatively charged side chain, plays a major role in intra and intermolecular interactions of proteins, peptides, and enzymes. An exhaustive conformational analysis has been performed for all eight possible forms at B3LYP/cc-pVTZ level. All possible neutral, zwitterionic, protonated, and deprotonated forms of glutamic acid structures have been investigated in solution by using polarizable continuum model mimicking water as the solvent. Nine families based on the dihedral angles have been classified for eight glutamic acid forms. The electrostatic effects included in the solvent model usually stabilize the charged forms more. However, the stability of the zwitterionic form has been underestimated due to the lack of hydrogen bonding between the solute and solvent; therefore, it is observed that compact neutral glutamic acid structures are more stable in solution than they are in vacuum. Our calculations have shown that among all eight possible forms, some are not stable in solution and are immediately converted to other more stable forms. Comparison of isoelectronic glutamic acid forms indicated that one of the structures among possible zwitterionic and anionic forms may dominate over the other possible forms. Additional investigations using explicit solvent models are necessary to determine the stability of charged forms of glutamic acid in solution as our results clearly indicate that hydrogen bonding and its type have a major role in the structure and energy of conformers.
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Meng L, Wang Z, Zhang J, Zhou M, Wu W. Low Energy Conformations and Gas-Phase Acidity and Basicity of Pyrrolysine. J Phys Chem A 2014; 118:7085-95. [DOI: 10.1021/jp503444h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Lingbiao Meng
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Zhuo Wang
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Jicheng Zhang
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Minjie Zhou
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Weidong Wu
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
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Meng L, Wu W, Zhang J. Gas Phase Conformations of Selenocysteine and Related Ions: A Comprehensive Theoretical Study. J Phys Chem A 2014; 118:1684-96. [DOI: 10.1021/jp411403w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Lingbiao Meng
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Weidong Wu
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
| | - Jicheng Zhang
- Research Center of Laser
Fusion, China Academy of Engineering Physics, Mianyang 621900, China
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Dunbar RC. Spectroscopy of Metal-Ion Complexes with Peptide-Related Ligands. Top Curr Chem (Cham) 2014; 364:183-223. [DOI: 10.1007/128_2014_578] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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36
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Gupta M, da Silva EF, Svendsen HF. Explicit Solvation Shell Model and Continuum Solvation Models for Solvation Energy and pKa Determination of Amino Acids. J Chem Theory Comput 2013; 9:5021-37. [DOI: 10.1021/ct400459y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mayuri Gupta
- Department
of Chemical Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Eirik F. da Silva
- Department
of Process Technology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Hallvard F. Svendsen
- Department
of Chemical Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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37
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Thorough theoretical search of conformations of neutral, protonated and deprotonated glutamine in gas phase. COMPUT THEOR CHEM 2013. [DOI: 10.1016/j.comptc.2013.07.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Amorim Madeira PJ, Vaz PD, Bettencourt da Silva RJN, Florêncio MH. Can Semi-empirical Calculations Help Solve Mass Spectrometry Problems? Protonation Sites and Proton Affinities of Amino Acids. Chempluschem 2013; 78:1149-1156. [DOI: 10.1002/cplu.201300173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/19/2013] [Indexed: 11/10/2022]
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Schmidt J, Kass SR. Zwitterion vs Neutral Structures of Amino Acids Stabilized by a Negatively Charged Site: Infrared Photodissociation and Computations of Proline–Chloride Anion. J Phys Chem A 2013; 117:4863-9. [DOI: 10.1021/jp402267c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Jacob Schmidt
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Steven R. Kass
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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40
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Riffet V, Bouchoux G. Gas-phase structures and thermochemistry of neutral histidine and its conjugated acid and base. Phys Chem Chem Phys 2013; 15:6097-106. [DOI: 10.1039/c3cp00043e] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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41
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Song T, Ma CY, Chu IK, Siu CK, Laskin J. Mechanistic Examination of Cβ–Cγ Bond Cleavages of Tryptophan Residues during Dissociations of Molecular Peptide Radical Cations. J Phys Chem A 2012; 117:1059-68. [PMID: 22697598 DOI: 10.1021/jp303562e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tao Song
- Department
of Chemistry and ‡School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Ching-Yung Ma
- Department
of Chemistry and ‡School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Ivan K. Chu
- Department
of Chemistry and ‡School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Chi-Kit Siu
- Department
of Biology and Chemistry, City University of Hong Kong, Hong Kong,
China
| | - Julia Laskin
- Chemical
and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, Washington
99354, United States
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43
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Roux MV, Notario R, Segura M, Chickos JS, Liebman JF. The enthalpy of formation of methionine revisited. J PHYS ORG CHEM 2012. [DOI: 10.1002/poc.2961] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- María Victoria Roux
- Institute of Physical Chemistry “Rocasolano”; CSIC; Serrano 119 28006 Madrid Spain
| | - Rafael Notario
- Institute of Physical Chemistry “Rocasolano”; CSIC; Serrano 119 28006 Madrid Spain
| | - Marta Segura
- Perkin Elmer España S.L.; Ronda de Poniente 19, 28760 Tres Cantos Madrid Spain
| | - James S. Chickos
- Department of Chemistry and Biochemistry; University of Missouri-St. Louis; One University Boulevard St. Louis Missouri 63121-4499 USA
| | - Joel F. Liebman
- Department of Chemistry and Biochemistry; University of Maryland; Baltimore County Baltimore MD 21250 USA
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44
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Bouchoux G. Gas phase basicities of polyfunctional molecules. Part 3: Amino acids. MASS SPECTROMETRY REVIEWS 2012; 31:391-435. [PMID: 22611554 DOI: 10.1002/mas.20349] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The present article is the third part of a general overview of the gas-phase protonation thermochemistry of polyfunctional molecules (first part: Mass Spectrom. Rev., 2007, 26:775-835, second part: Mass Spectrom. Rev., 2011, in press). This review is devoted to the 20 proteinogenic amino acids and is divided in two parts. In the first one, the experimental data obtained during the last 30 years using the equilibrium, thermokinetic and kinetic methods are presented. A general re-assignment of the values originating from these various experiments has been done on the basis of the commonly accepted Hunter & Lias 1998 gas-phase basicity scale in order to provide an homogeneous set of data. In the second part, theoretical investigations on gaseous neutral and protonated amino acids are reviewed. Conformational landscapes of both types of species were examined in order to provide theoretical protonation thermochemistry based on the truly identified most stable conformers. Proton affinities computed at the presently highest levels of theory (i.e. composite methods such as Gn procedures) are presented. Estimates of thermochemical parameters calculated using a Boltzmann distribution of conformers at 298K are also included. Finally, comparison between experiment and theory is discussed and a set of evaluated proton affinities, gas-phase basicities and protonation entropies is proposed.
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Affiliation(s)
- Guy Bouchoux
- Département de Chimie, Laboratoire des Mécanismes Réactionnels, Ecole Polytechnique, 91120 Palaiseau, France.
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Uddin KM, Warburton PL, Poirier RA. Comparisons of Computational and Experimental Thermochemical Properties of α-Amino Acids. J Phys Chem B 2012; 116:3220-34. [DOI: 10.1021/jp210948m] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Kabir M. Uddin
- Department of Chemistry, Memorial University, St. John’s, Newfoundland A1B 3X7, Canada
| | - Peter L. Warburton
- Department of Chemistry, Memorial University, St. John’s, Newfoundland A1B 3X7, Canada
| | - Raymond A. Poirier
- Department of Chemistry, Memorial University, St. John’s, Newfoundland A1B 3X7, Canada
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Stover ML, Jackson VE, Matus MH, Adams MA, Cassady CJ, Dixon DA. Fundamental Thermochemical Properties of Amino Acids: Gas-Phase and Aqueous Acidities and Gas-Phase Heats of Formation. J Phys Chem B 2012; 116:2905-16. [DOI: 10.1021/jp207271p] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michele L. Stover
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
| | - Virgil E. Jackson
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
| | - Myrna H. Matus
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
| | - Margaret A. Adams
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
| | - Carolyn J. Cassady
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
| | - David A. Dixon
- Chemistry
Department, The University of Alabama, Shelby Hall, Box 870336,
Tuscaloosa, Alabama 35487-0336, United States
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47
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Meng L, Lin Z. Comprehensive computational study of gas-phase conformations of neutral, protonated and deprotonated glutamic acids. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2011.07.037] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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48
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Saminathan IS, Zhao J, Siu KWM, Hopkinson AC. Doubly charged protonated a ions derived from small peptides. Phys Chem Chem Phys 2011; 13:18307-14. [PMID: 21773645 DOI: 10.1039/c1cp21522a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Protonated a(2) and a(3) (therefore doubly charged) ions in which both charges lie on the peptide backbone are formed in collision-induced dissociations of [La(III)(peptide)(CH(3)CN)(m)](3+) complexes. Abundant (a(3)+H)(2+) ions are formed from triproline (PPP) and peptides with a proline residue at the N-terminus; these peptides are the most effective in producing ions of the type (a(2)+H)(2+) and (a(3)+H)(2+). A systematic study of the effect of the location of the proline residue and other residues of aliphatic amino acids on the generation of protonated a ions is reported. Density functional theory calculations at B3LYP/6-311++G(d,p) gave the proton affinity of the a(3) ion derived from PPP to be 167.6 kcal mol(-1), 2.6 kcal mol(-1) higher than that of water. The protonated a(2) ions of diglycine and diproline and a(3) ions of triglycine have lower proton affinities and are only observed in lower abundances, possibly due to proton transfer to water in ion-molecule reactions.
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Affiliation(s)
- Irine S Saminathan
- Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Canada M3J 1P3
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49
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Harrison AG. Effect of the identity of Xaa on the fragmentation modes of doubly-protonated Ala-Ala-Xaa-Ala-Ala-Ala-Arg. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:906-911. [PMID: 21472525 DOI: 10.1007/s13361-011-0091-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 01/20/2011] [Accepted: 01/22/2011] [Indexed: 05/30/2023]
Abstract
The product ion mass spectra resulting from collisional activation of doubly-protonated tryptic-type peptides Ala-Ala-Xaa-Ala-Ala-Ala-Arg have been determined for Xaa = Ala(A), Ser(S), Val(V), Thr(T), Ile(I), Phe(F), Tyr(Y), Sar, Met(M), Trp(W), Pro(P), and Gln(Q). The major fragmentation reaction involves cleavage of the second amide bond (counting from the N-terminus) except for Xaa = Ser and Thr where elimination of H(2)O from the [M + 2H](+2) ion forms the base peak. In general, the extent of cleavage of the second amide bond shows little dependence on the identity of Xaa and little dependence on whether the bond cleavage involves symmetrical bond cleavage to form a y(5)/b(2) ion pair or asymmetrically to form y (5) (+2) and a neutral b(2) species. Notable exceptions to this generalization occur for Xaa equal to Pro or Sar. For Xaa = Pro only cleavage of the second amide bond is observed, consistent with a pronounced proline effect, i.e., cleavage N-terminal to Pro. When Xaa = Sar considerably enhanced cleavage of the second amide bond also is observed, suggesting that at least part of the proline effect relates to the tertiary nature of the amide nitrogen. In the competition between symmetric and asymmetric bond cleavage an attempt to establish a linear free energy correlation in relating ln(y(5)(+2)/y(5)) to PA(H-Xaa-OH) did not lead to a reasonable correlation although the trend of increasing y(5)(+2)/y(5) ratio with increasing proton affinity of H-Xaa-OH was clear. Proline showed a unique behavior in giving a much higher y(5)(+2)/y(5) ratio than any of the other residues studied.
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Affiliation(s)
- Alex G Harrison
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada.
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50
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Song T, Ng DCM, Quan Q, Siu CK, Chu IK. Arginine-Facilitated α- and π-Radical Migrations in Glycylarginyltryptophan Radical Cations. Chem Asian J 2011; 6:888-98. [DOI: 10.1002/asia.201000677] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Indexed: 12/16/2022]
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