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Bolognesi P, Avaldi L. Photoelectron-photoion(s) coincidence studies of molecules of biological interest. Phys Chem Chem Phys 2022; 24:22356-22370. [PMID: 36124990 DOI: 10.1039/d2cp03079a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoelectron-photoion(s) coincidence, PEPICO, experiments with synchrotron radiation have become one of the most powerful tools to investigate dissociative photoionization thanks to their selectivity. In this paper their application to the study of molecular species of biological interest in the gas phase is reviewed. Some applications of PEPICO to the study of potential radiosensitizers, amino acids and small peptides and opportunities offered by the advent of novel methods for the production of beams of these molecules are discussed.
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Affiliation(s)
- P Bolognesi
- CNR-Istituto di Struttura della Materia, Area della Ricerca di Roma 1, CP 10 00015 Monterotondo Scalo, Italy.
| | - L Avaldi
- CNR-Istituto di Struttura della Materia, Area della Ricerca di Roma 1, CP 10 00015 Monterotondo Scalo, Italy.
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2
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Staemmler V. Wavefunction-based quantum-chemical ab initiocalculations for core electron binding energies of small open shell molecules. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:354004. [PMID: 35700722 DOI: 10.1088/1361-648x/ac78b9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Core electron binding energies (CEBEs), i.e. ionization energies of 1s core orbitals, are calculated by means of wavefunction-based quantum-chemicalab initiomethods for a series of small open-shell molecules containing first-row atoms. The calculations are performed in three steps: (a) Koopmans' theorem, where the orbitals of the electronic ground state are used unchanged also for the ions, (b) Hartree-Fock or self consistent field (SCF) approximation in which the orbitals are allowed to relax after 1s ionization (ΔSCF), (c) dynamic correlation effects on top of SCF. For open-shell molecules 1s ionization leads to ions in several spin states, mostly to a pair of a triplet and a singlet state. In several cases one or both of these ionic states are only poorly described by a single-reference SCF wavefunction, therefore a multi-reference complete active space self consistent field (CAS-SCF) wavefunction is used instead. The correlation effects are evaluated by means of our multi-reference coupled electron pair approximation program. The accuracy of the calculated CEBEs is in the order of 0.1-0.4 eV. This is in agreement with experimental results for NO and O2. But there exist only very few gas phase data for CEBEs of open-shell molecules.
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Affiliation(s)
- Volker Staemmler
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
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3
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Chiarinelli J, Barreiro-Lage D, Bolognesi P, RICHTER R, Zettergren H, Stockett MH, Díaz-Tendero S, Avaldi L. Electron and ion spectroscopy of the cyclo-alanine-alanine dipeptide. Phys Chem Chem Phys 2022; 24:5855-5867. [DOI: 10.1039/d1cp05811h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The VUV photoionisation and photofragmentation of cyclo-alanine-alanine (cAA) has been studiedin a joint experimental and theoretical work. The photoelectron spectrum and the photoelectron-photoion coincidence (PEPICO) measurements, which enable a control...
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4
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Moore B, Toh SY, Wong YTA, Bashiri T, McKinnon A, Wai Y, Alethea Lee KW, Ovchinnikov P, Chiang CY, Djuricanin P, Momose T. Hydrocarboxyl Radical as a Product of α-Alanine Ultraviolet Photolysis. J Phys Chem Lett 2021; 12:11992-11997. [PMID: 34889613 DOI: 10.1021/acs.jpclett.1c03104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
UV photodissociation of α-alanine was studied by parahydrogen matrix isolation infrared spectroscopy. The temporal behavior of Fourier transform infrared spectra revealed that UV irradiation at 213 nm yielded the HOCO radical as a direct photoproduct from the S2 excited state. The concentration of HOCO quickly approached a steady state due to secondary photodissociation of HOCO to produce CO2 + H or CO + OH. On the other hand, no photoproducts were detected by S1 excitation at 266 nm. Irradiation of fully deuterated α-alanine at 213 nm yielded ∼2 times more cis-DOCO radicals than the lower energy isomer trans-DOCO, indicating that the conformation of the hydroxyl group is fairly well-preserved upon photodissociation of α-alanine. The present study suggests that HOCO may be a good tracer species in the search for amino acids in interstellar space.
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Affiliation(s)
- Brendan Moore
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Shin Yi Toh
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Y T Angel Wong
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Termeh Bashiri
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Alexandra McKinnon
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Yonnie Wai
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Ka Wing Alethea Lee
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Polina Ovchinnikov
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Chih-Yu Chiang
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Pavle Djuricanin
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Takamasa Momose
- Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
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David J, Gómez S, Guerra D, Guerra D, Restrepo A. A Comprehensive Picture of the Structures, Energies, and Bonding in the Alanine Dimers. Chemphyschem 2021; 22:2401-2412. [PMID: 34554628 DOI: 10.1002/cphc.202100585] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/22/2021] [Indexed: 12/14/2022]
Abstract
High level quantum mechanical computations and extensive stochastic searches of the potential energy surfaces of the Alanine dimers uncover rich and complex structural and interaction landscapes. A total of 416 strongly bound (up 13.4 kcal mol-1 binding energies at the DLPNO-CCSD(T)/6-311++G(d,p) level corrected by the basis set superposition error and by the zero point vibrational energies over B3LYP-D3 geometries), close energy equilibrium structures were located, bonded via 32 specific types of intermolecular contacts including Y⋅⋅⋅H-X primary and Y⋅⋅⋅H-C secondary hydrogen bonds, H⋅⋅⋅H dihydrogen contacts, and non conventional anti-electrostatic Y δ - ⋯ X δ - interactions. The putative global minimum is triply degenerate, corresponding to the structure of the common dimer of a carboxylic acid. All quantum descriptors of chemical bonding point to a multitude of weak individual interactions within each dimer, whose cumulative effect results in large binding energies and in an attractive fluxional wall of non-covalent interactions in the interstitial region between the monomers.
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Affiliation(s)
- Jorge David
- Escuela de Ciencias, Departamento de Ciencias Físicas, Universidad Eafit, AA 3300, Medellín, Colombia
| | - Sara Gómez
- Scuola Normale Superiore, Classe di Scienze, Piazza dei Cavalieri 7, 56126, Pisa, Italy
| | - Doris Guerra
- Instituto de Química, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia
| | - Dario Guerra
- Departamento de Educación y Ciencias Básicas, Instituto Tecnológico Metropolitano, Calle 73 No. 76 A-354, Medellín, Colombia
| | - Albeiro Restrepo
- Instituto de Química, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia
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6
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Kostko O, Xu B, Ahmed M. Local electronic structure of histidine in aqueous solution. Phys Chem Chem Phys 2021; 23:8847-8853. [DOI: 10.1039/d1cp00361e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
X-Ray spectroscopy coupled with DFT calculations reveals the pH dependent electronic structure of an amino acid in an aqueous environment.
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Affiliation(s)
- O. Kostko
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
- Advanced Light Source
| | - B. Xu
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - M. Ahmed
- Chemical Sciences Division
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
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7
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Gloaguen E, Mons M, Schwing K, Gerhards M. Neutral Peptides in the Gas Phase: Conformation and Aggregation Issues. Chem Rev 2020; 120:12490-12562. [PMID: 33152238 DOI: 10.1021/acs.chemrev.0c00168] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Combined IR and UV laser spectroscopic techniques in molecular beams merged with theoretical approaches have proven to be an ideal tool to elucidate intrinsic structural properties on a molecular level. It offers the possibility to analyze structural changes, in a controlled molecular environment, when successively adding aggregation partners. By this, it further makes these techniques a valuable starting point for a bottom-up approach in understanding the forces shaping larger molecular systems. This bottom-up approach was successfully applied to neutral amino acids starting around the 1990s. Ever since, experimental and theoretical methods developed further, and investigations could be extended to larger peptide systems. Against this background, the review gives an introduction to secondary structures and experimental methods as well as a summary on theoretical approaches. Vibrational frequencies being characteristic probes of molecular structure and interactions are especially addressed. Archetypal biologically relevant secondary structures investigated by molecular beam spectroscopy are described, and the influences of specific peptide residues on conformational preferences as well as the competition between secondary structures are discussed. Important influences like microsolvation or aggregation behavior are presented. Beyond the linear α-peptides, the main results of structural analysis on cyclic systems as well as on β- and γ-peptides are summarized. Overall, this contribution addresses current aspects of molecular beam spectroscopy on peptides and related species and provides molecular level insights into manifold issues of chemical and biochemical relevance.
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Affiliation(s)
- Eric Gloaguen
- CEA, CNRS, Université Paris-Saclay, CEA Paris-Saclay, Bât 522, 91191 Gif-sur-Yvette, France
| | - Michel Mons
- CEA, CNRS, Université Paris-Saclay, CEA Paris-Saclay, Bât 522, 91191 Gif-sur-Yvette, France
| | - Kirsten Schwing
- TU Kaiserslautern & Research Center Optimas, Erwin-Schrödinger-Straße 52, D-67663 Kaiserslautern, Germany
| | - Markus Gerhards
- TU Kaiserslautern & Research Center Optimas, Erwin-Schrödinger-Straße 52, D-67663 Kaiserslautern, Germany
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8
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Oliveira CX, Mocellin A, Menezes de Souza Lima F, Jesus Chaves Neto AM, Lima Azevedo D. DFT Study of L‐Cysteine Fragmentation Route using a Novel Protocol. ChemistrySelect 2019. [DOI: 10.1002/slct.201903453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Carlos Xavier Oliveira
- Institute of Physics University of Brasília Campus Darcy Ribeiro, Asa Norte Brasília-DF Brazil 70919-970
| | - Alexandra Mocellin
- Institute of Physics University of Brasília Campus Darcy Ribeiro, Asa Norte Brasília-DF Brazil 70919-970
| | | | | | - David Lima Azevedo
- Institute of Physics University of Brasília Campus Darcy Ribeiro, Asa Norte Brasília-DF Brazil 70919-970
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9
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Castrovilli MC, Bolognesi P, Bodo E, Mattioli G, Cartoni A, Avaldi L. An experimental and theoretical investigation of XPS and NEXAFS of 5-halouracils. Phys Chem Chem Phys 2018; 20:6657-6667. [PMID: 29457179 DOI: 10.1039/c8cp00026c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The C, N and O 1s excitation and ionization processes of 5X-uracil (X = F, Cl, Br, and I) were investigated using near edge X-ray absorption fine structure (NEXAFS) and X-ray photoemission (XPS) spectroscopies. This study aims at the fine assessment of the effects of the functionalization of uracil molecules by halogen atoms having different electronegativity and bound to the same molecular site. Two DFT-based approaches, which rely on different paradigms, have been used to simulate the experimental spectra and to assign the corresponding features. The analysis of the screening of the core holes of the different atoms via electronic charge density plots has turned out to be a useful tool to illustrate the competition between the partially aromatic and partially conjugate properties of this class of molecules.
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Affiliation(s)
- M C Castrovilli
- Istituto di Struttura della Materia-CNR, ISM-CNR, Area della Ricerca di Roma 1, CP10, 00015 Monterotondo Scalo, Italy.
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10
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Benchmarking density functionals and Gaussian basis sets for calculation of core-electron binding energies in amino acids. Theor Chem Acc 2017. [DOI: 10.1007/s00214-017-2115-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Xu B, Jacobs MI, Kostko O, Ahmed M. Guanidinium Group Remains Protonated in a Strongly Basic Arginine Solution. Chemphyschem 2017; 18:1503-1506. [DOI: 10.1002/cphc.201700197] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Bo Xu
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Michael I. Jacobs
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
- Department of Chemistry University of California Berkeley CA 94720 USA
| | - Oleg Kostko
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Musahid Ahmed
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
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12
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Abstract
We introduce a general theoretical approach for the simulation of photochemical dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochemistry. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. We show that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochemistry of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7%, which is also in good correspondence to the experimental findings. Our method is generally applicable to complex systems and might serve to systematically explore the photochemical origin of homochirality.
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Affiliation(s)
- Matthias Wohlgemuth
- Institute for Physical and Theoretical Chemistry, Julius Maximilians University Würzburg , Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - Roland Mitrić
- Institute for Physical and Theoretical Chemistry, Julius Maximilians University Würzburg , Emil-Fischer-Str. 42, 97074 Würzburg, Germany
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13
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Abstract
This chapter examines the structural characterisation of isolated neutral amino-acids and peptides. After a presentation of the experimental and theoretical state-of-the-art in the field, a review of the major structures and shaping interactions is presented. Special focus is made on conformationally-resolved studies which enable one to go beyond simple structural characterisation; probing flexibility and excited-state photophysics are given as examples of promising future directions.
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14
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Förstel M, Neustetter M, Denifl S, Lelievre F, Hergenhahn U. A source for microhydrated biomolecules. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:073103. [PMID: 26233352 DOI: 10.1063/1.4923247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We describe the construction of an apparatus for the production of a molecular jet of microhydrated biomolecules. Our design uses a water reservoir producing water vapour, which then passes through a separate reservoir containing a vapour of a sublimated biomolecule. The mixture coexpands into a molecular beam apparatus through a conical nozzle. Mass spectra showing water-adenin and water-uracil complexes are shown as typical examples. Suitable expansion conditions are reached without the use of an inert carrier gas.
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Affiliation(s)
- M Förstel
- Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald, Germany
| | - M Neustetter
- Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - S Denifl
- Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria
| | - F Lelievre
- Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald, Germany
| | - U Hergenhahn
- Max-Planck-Institut für Plasmaphysik, Wendelsteinstraße 1, 17491 Greifswald, Germany
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15
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Wang F, Ahmed M. Sitting above the maze: recent model discoveries in molecular science. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.923570] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Tia M, Cunha de Miranda B, Daly S, Gaie-Levrel F, Garcia GA, Nahon L, Powis I. VUV photodynamics and chiral asymmetry in the photoionization of gas phase alanine enantiomers. J Phys Chem A 2014; 118:2765-79. [PMID: 24654892 DOI: 10.1021/jp5016142] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The valence shell photoionization of the simplest proteinaceous chiral amino acid, alanine, is investigated over the vacuum ultraviolet region from its ionization threshold up to 18 eV. Tunable and variable polarization synchrotron radiation was coupled to a double imaging photoelectron/photoion coincidence (i(2)PEPICO) spectrometer to produce mass-selected threshold photoelectron spectra and derive the state-selected fragmentation channels. The photoelectron circular dichroism (PECD), an orbital-sensitive, conformer-dependent chiroptical effect, was also recorded at various photon energies and compared to continuum multiple scattering calculations. Two complementary vaporization methods-aerosol thermodesorption and a resistively heated sample oven coupled to an adiabatic expansion-were applied to promote pure enantiomers of alanine into the gas phase, yielding neutral alanine with different internal energy distributions. A comparison of the photoelectron spectroscopy, fragmentation, and dichroism measured for each of the vaporization methods was rationalized in terms of internal energy and conformer populations and supported by theoretical calculations. The analytical potential of the so-called PECD-PICO detection technique-where the electron spectroscopy and circular dichroism can be obtained as a function of mass and ion translational energy-is underlined and applied to characterize the origin of the various species found in the experimental mass spectra. Finally, the PECD findings are discussed within an astrochemical context, and possible implications regarding the origin of biomolecular asymmetry are identified.
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Affiliation(s)
- Maurice Tia
- Synchrotron SOLEIL, l'Orme des Merisiers, Saint Aubin BP 48, 91192 Gif sur Yvette Cedex, France
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17
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Farrokhpour H, Ghandehari M. Photoelectron Spectra of Some Important Biological Molecules: Symmetry-Adapted-Cluster Configuration Interaction Study. J Phys Chem B 2013; 117:6027-41. [DOI: 10.1021/jp311213c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Hossein Farrokhpour
- Chemistry Department, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Maryam Ghandehari
- Chemistry Department, Isfahan University of Technology, Isfahan, 84156-83111, Iran
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19
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Blum M, Odelius M, Weinhardt L, Pookpanratana S, Bär M, Zhang Y, Fuchs O, Yang W, Umbach E, Heske C. Ultrafast Proton Dynamics in Aqueous Amino Acid Solutions Studied by Resonant Inelastic Soft X-ray Scattering. J Phys Chem B 2012; 116:13757-64. [DOI: 10.1021/jp302958j] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M. Blum
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
- Experimentelle Physik
VII, Universität Würzburg, Würzburg, Germany
| | - M. Odelius
- Fysikum, Albanova University Center, Stockholm University, Stockholm, Sweden
| | - L. Weinhardt
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
- Experimentelle Physik
VII, Universität Würzburg, Würzburg, Germany
| | - S. Pookpanratana
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
| | - M. Bär
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
- Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
- Brandenburgische Technische Universität, Cottbus, Germany
| | - Y. Zhang
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
| | - O. Fuchs
- Experimentelle Physik
VII, Universität Würzburg, Würzburg, Germany
| | - W. Yang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States
| | | | - C. Heske
- Department of Chemistry, University of Nevada, Las Vegas, Nevada,
United States
- Institute for Chemical
Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany
- ANKA Synchrotron
Radiation Facility, Karlsruhe Institute of Technology, Karlsruhe, Germany
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20
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Farrokhpour H, Fathi F, De Brito AN. Theoretical and Experimental Study of Valence Photoelectron Spectrum of d,l-Alanine Amino Acid. J Phys Chem A 2012; 116:7004-15. [DOI: 10.1021/jp3023716] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- H. Farrokhpour
- Chemistry Department, Isfahan University of Technology, Isfahan 84156-83111,
Iran
| | - F. Fathi
- Chemistry Department, Isfahan University of Technology, Isfahan 84156-83111,
Iran
| | - A. Naves De Brito
- Laboratório Nacional de Luz Síncrotron (LNLS), Box 6192-CEP,
13084-971 Campinas-Sp, Brazil
- Instituto de Física “Gleb
Wataghin”, Universidade Estadual de Campinas, 13083-859 Campinas-SP, Brazil
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21
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Lago A, Oliva J, Dávalos J. Experimental and theoretical investigation of the parabanic acid molecule following VUV excitation and photodissociation. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2011.11.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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22
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Ganesan A, Wang F, Brunger M, Prince K. Effects of alkyl side chains on properties of aliphatic amino acids probed using quantum chemical calculations. JOURNAL OF SYNCHROTRON RADIATION 2011; 18:733-742. [PMID: 21862853 DOI: 10.1107/s0909049511029499] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 07/21/2011] [Indexed: 05/31/2023]
Abstract
Effects of alkyl side chains (R-) on the electronic structural properties of aliphatic amino acids are investigated using quantum mechanical approaches. The carbon (C 1s) binding energy spectra of the aliphatic amino acids are derived from the C 1s spectrum of glycine (the parent spectrum) by the addition of spectral peaks, depending on the alkyl side chains, appearing in the lower energy region IP < 290 eV (where IP is the ionization potential). The two glycyl parent spectral peaks of the amide 291.0 eV [C((2))] and carboxylic 293.5 eV [C((1))] C atoms are shifted in the aliphatic amino acids owing to perturbations depending on the size and structure of the alkyl chains. The pattern of the N 1s and O 1s spectra in glycine is retained in the spectra of the other amino acids with small shifts to lower energy, again depending on the alkyl side chain. The Hirshfeld charge analyses confirm the observations. The alkyl effects on the valence binding energy spectra of the amino acids are concentrated in the middle valence energy region of 12-16 eV, and hence this energy region of 12-16 eV is considered as the `fingerprint' of the alkyl side chains. Selected valence orbitals, either inside or outside of the alkyl fingerprint region, are presented using both density distributions and orbital momentum distributions, in order to understand the chemical bonding of the amino acids. It is also observed that the HOMO-LUMO energy gaps of the aliphatic amino acids are reduced with the growth of the alkyl side chain.
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Affiliation(s)
- Aravindhan Ganesan
- Faculty of Life and Social Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
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23
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Selvam L, Chen FF, Wang F. Methylation of zebularine investigated using density functional theory calculations. J Comput Chem 2011; 32:2077-83. [PMID: 21541952 DOI: 10.1002/jcc.21785] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 12/01/2010] [Accepted: 02/10/2011] [Indexed: 11/09/2022]
Abstract
Deoxyribonucleic acid (DNA) methylation is an epigenetic phenomenon, which adds methyl groups into DNA. This study reveals methylation of a nucleoside antibiotic drug 1-(β-D-ribofuranosyl)-2-pyrimidinone (zebularine or zeb) with respect to its methylated analog, 1-(β-D-ribofuranosyl)-5-methyl-2-pyrimidinone (d5) using density functional theory calculations in valence electronic space. Very similar infrared spectra suggest that zeb and d5 do not differ by types of the chemical bonds, but distinctly different Raman spectra of the nucleoside pair reveal that the impact caused by methylation of zeb can be significant. Further valence orbital-based information details on valence electronic structural changes caused by methylation of zebularine. Frontier orbitals in momentum space and position space of the molecules respond differently to methylation. Based on the additional methyl electron density concentration in d5, orbitals affected by the methyl moiety are classified into primary and secondary contributors. Primary methyl contributions include MO8 (57a), MO18 (47a), and MO37 (28a) of d5, which concentrates on methyl and the base moieties, suggest certain connection to their Frontier orbitals. The primary and secondary methyl affected orbitals provide useful information on chemical bonding mechanism of the methylation in zebularine.
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Affiliation(s)
- Lalitha Selvam
- Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, Hawthorn, Melbourne, Victoria 3122 Australia
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24
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Ramaniah LM, Chakrabarti A, Kshirsagar R, Kamal C, Banerjee A. Density functional study of α-amino acids: structural, energetic and vibrational properties. Mol Phys 2011. [DOI: 10.1080/00268976.2011.558027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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25
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Close DM. Calculated vertical ionization energies of the common α-amino acids in the gas phase and in solution. J Phys Chem A 2011; 115:2900-12. [PMID: 21410277 DOI: 10.1021/jp200503z] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The vertical ionization energies of the low-lying conformers of the α-amino acids found in proteins have been calculated. Geometry optimizations were first performed at the B3LYP/6-311G(d,p) level of theory, and then reoptimized at the MP2/6-311G(d,p) level of theory. Vertical ionization energies were then computed by three methods, electron propagator in the partial third-order (P3) approximation, Outer-Valence-Green's Functions, and by evaluating the difference in the total energy between the cation radical and the neutral amino acid in the geometry of the neutral species. When available, the results are compared to the experimental vertical ionization energies. The vertical ionization energies calculated using the MP2/P3 method gave the best overall agreement with the experimental results. Next, the ionization energies in solution are calculated for the zwitterionic forms of the α-amino acids by using IEFPCM methods. To obtain the vertical ionization energy in solution, it is necessary to use the nonequilibrium polarizable continuum model (NEPCM), the results of which are reported here for the α-amino acids.
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Affiliation(s)
- David M Close
- Department of Physics, Box 70652, East Tennessee State University, Johnson City, Tennessee 37614, United States.
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26
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Gao YK, Traeger F, Kotsis K, Staemmler V. A theoretical study of the XP and NEXAFS spectra of alanine: gas phase molecule, crystal, and adsorbate at the ZnO(101̄0) surface. Phys Chem Chem Phys 2011; 13:10709-18. [DOI: 10.1039/c0cp02295k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Bolognesi P, O'Keeffe P, Ovcharenko Y, Coreno M, Avaldi L, Feyer V, Plekan O, Prince KC, Zhang W, Carravetta V. Pyrimidine and halogenated pyrimidines near edge x-ray absorption fine structure spectra at C and N K-edges: experiment and theory. J Chem Phys 2010; 133:034302. [PMID: 20649325 DOI: 10.1063/1.3442489] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The inner shell excitation of pyrimidine and some halogenated pyrimidines near the C and N K-edges has been investigated experimentally by near edge x-ray absorption fine structure spectroscopy and theoretically by density functional theory calculations. The selected targets, 5-Br-pyrimidine, 2-Br-pyrimidine, 2-Cl-pyrimidine, and 5-Br-2-Cl-pyrimidine, allow the effects of the functionalization of the pyrimidine ring to be studied either as a function of different halogen atoms bound to the same molecular site or as a function of the same halogen atom bound to different molecular sites. The results show that the individual characteristics of the different spectra of the substituted pyrimidines can be rationalized in terms of variations in electronic and geometrical structures of the molecule depending on the localization and the electronegativity of the substituent.
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Affiliation(s)
- P Bolognesi
- CNR-IMIP, Area della Ricerca di Roma 1, Monterotondo Scalo 00016, Italy.
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28
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29
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Ganesan A, Wang F, Falzon C. Intramolecular interactions of L-phenylalanine: Valence ionization spectra and orbital momentum distributions of its fragment molecules. J Comput Chem 2010; 32:525-35. [DOI: 10.1002/jcc.21639] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 05/24/2010] [Accepted: 06/23/2010] [Indexed: 01/12/2023]
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30
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The gas phase conformers and vibrational spectra of valine, leucine and isoleucine: An ab initio study. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.theochem.2010.04.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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31
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Vibrational and electronic characterisation of Staphylococcus aureus wall teichoic acids and relevant components in thin films. Anal Bioanal Chem 2010; 397:2429-37. [PMID: 20506013 DOI: 10.1007/s00216-010-3832-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2010] [Revised: 04/29/2010] [Accepted: 05/05/2010] [Indexed: 10/19/2022]
Abstract
This work reports an investigation of S. aureus wall teichoic acid (WTA) and compares this biopolymer with its major occurring components, D: -alanine and glycerol phosphate. Detailed insight into molecular structures and electronic properties is obtained by vibrational and photoemission spectroscopy. Calculations are performed to support the analysis of our experimental vibrational spectra. It is shown that there are contributions of positive and negative charges in WTAs, but the number of negative charges is expected to be higher. The presence of both positive and negative charges on WTA may offer a route for modification of surfaces with the objective of avoiding the formation of biofilms.
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32
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Bolognesi P, Mattioli G, O'Keeffe P, Feyer V, Plekan O, Ovcharenko Y, Prince KC, Coreno M, Amore Bonapasta A, Avaldi L. Investigation of halogenated pyrimidines by X-ray photoemission spectroscopy and theoretical DFT methods. J Phys Chem A 2010; 113:13593-600. [PMID: 19929014 DOI: 10.1021/jp908512v] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The inner shell ionization of pyrimidine and some halogenated pyrimidines has been investigated experimentally by X-ray photoemission spectroscopy (XPS) and theoretically by density functional theory (DFT) methods. The selected targets-5-Br-pyrimidine, 2-Br-pyrimidine, 2-Cl-pyrimidine, and 5-Br-2-Cl-pyrimidine-allowed the study of the effect of the functionalization of the pyrimidine ring by different halogen atoms bound to the same molecular site, or by the same halogen atom bound to different molecular sites. The theoretical investigation of the inductive and resonance effects in the C(1s) ionization confirms the soundness of the resonance model for a qualitative description of the properties of an aromatic system. Moreover, the combination of the experimental results and the theoretical analysis provides a detailed description of the effects of the halogen atom on the screening of a C(1s) hole in the aromatic pyrimidine ring.
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Affiliation(s)
- P Bolognesi
- CNR-IMIP and CNR-ISM, Area della Ricerca di Roma 1, Via Salaria Km. 29.300, Monterotondo Scalo, Roma, Italy.
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33
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Bhattacharya A, Shin JW, Clawson KJ, Bernstein ER. Conformation specific and charge directed reactivity of radical cation intermediates of α-substituted (amino, hydroxy, and keto) bioactive carboxylic acids. Phys Chem Chem Phys 2010; 12:9700-12. [DOI: 10.1039/c003416a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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34
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Gronert S, Simpson DC, Conner KM. A reevaluation of computed proton affinities for the common alpha-amino acids. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:2116-2123. [PMID: 19683940 DOI: 10.1016/j.jasms.2009.07.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 07/01/2009] [Accepted: 07/01/2009] [Indexed: 05/28/2023]
Abstract
The proton affinities of the 20 common amino acids have been computed at the G3MP2 level using structures derived from broad conformational searches at a variety of levels including G3MP2. In some cases, the conformational surveys identified more stable species than had been used in previous studies of proton affinities, though the differences in energy are sometimes rather small. The present values are likely the most reliable measure of amino acid proton affinities in the gas phase. An analysis of differences between these values and those obtained experimentally via the kinetic method indicates that the extraction of proton affinities from kinetic method data can potentially lead to large errors linked to the estimation of relative protonation entropies.
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Affiliation(s)
- Scott Gronert
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, USA.
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35
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Ganesan A, Wang F. Intramolecular interactions of L-phenylalanine revealed by inner shell chemical shift. J Chem Phys 2009; 131:044321. [DOI: 10.1063/1.3187033] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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36
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Affiliation(s)
| | - Mark S. Gordon
- Department of Chemistry, Iowa State University, Ames, Iowa 50011
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37
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Feyer V, Plekan O, Richter R, Coreno M, Prince KC. Photoion mass spectroscopy and valence photoionization of hypoxanthine, xanthine and caffeine. Chem Phys 2009. [DOI: 10.1016/j.chemphys.2008.12.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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38
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Pan Y, Zhang L, Zhang T, Guo H, Hong X, Sheng L, Qi F. Intramolecular hydrogen transfer in the ionization process of α-alanine. Phys Chem Chem Phys 2009; 11:1189-95. [DOI: 10.1039/b813268b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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39
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40
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Kishor S, Dhayal S, Mathur M, Ramaniah LM. Structural and energetic properties ofα-amino acids: a first principles density functional study. Mol Phys 2008. [DOI: 10.1080/00268970802422577] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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41
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Feyer V, Plekan O, Richter R, Coreno M, Prince KC, Carravetta V. Core Level Study of Alanine and Threonine. J Phys Chem A 2008; 112:7806-15. [DOI: 10.1021/jp803017y] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Vitaliy Feyer
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Oksana Plekan
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Robert Richter
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Marcello Coreno
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Kevin C. Prince
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Vincenzo Carravetta
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti, Rome, I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
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42
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Catone D, Turchini S, Contini G, Zema N, Irrera S, Prosperi T, Stener M, Di Tommaso D, Decleva P. 2-amino-1-propanol versus 1-amino-2-propanol: Valence band and C 1s core-level photoelectron spectra. J Chem Phys 2007; 127:144312. [DOI: 10.1063/1.2798113] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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43
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Plekan O, Feyer V, Richter R, Coreno M, de Simone M, Prince KC, Carravetta V. Investigation of the Amino Acids Glycine, Proline, and Methionine by Photoemission Spectroscopy. J Phys Chem A 2007; 111:10998-1005. [DOI: 10.1021/jp075384v] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Oksana Plekan
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Vitaliy Feyer
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Robert Richter
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Marcello Coreno
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Monica de Simone
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Kevin C. Prince
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
| | - Vincenzo Carravetta
- Sincrotrone Trieste, Area Science Park, I-34012 Basovizza (Trieste), Italy, CNR-IMIP, Montelibretti (Rome), I-00016 Italy, Laboratorio Nazionale TASC, CNR-INFM, 34012 Trieste, Italy, and CNR-Institute of Chemical Physical Processes, Via Moruzzi 1, 56124 Pisa, Italy
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44
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Plekan O, Feyer V, Richter R, Coreno M, de Simone M, Prince K, Carravetta V. Photoemission and the shape of amino acids. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.05.110] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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45
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Thomas TD, Saethre LJ, Børve KJ, Gundersen M, Kukk E. Reactivity and core-ionization energies in conjugated dienes. Carbon 1s photoelectron spectroscopy of 1,3-pentadiene. J Phys Chem A 2007; 109:5085-92. [PMID: 16833862 DOI: 10.1021/jp051196y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The high-resolution carbon 1s photoelectron spectrum of trans-1,3-pentadiene has been resolved into contributions from the five inequivalent carbon atoms, and carbon 1s ionization energies have been assigned to each of these atoms. Spectra have also been measured for propene and 1,3-butadiene at better resolution than has previously been available. The ionization energies for the sp2 carbons are found to correlate well with activation energies for electrophilic addition and with proton affinities. Comparing the results for 1,3-pentadiene with those for ethene, propene, and 1,3-butadiene as well as with results of theoretical calculations makes it is possible to assess the effect of the terminal methyl group in 1,3-pentadiene. As in propene, the methyl group contributes electrons to the beta carbon through the pi system. In addition, there is a significant (though smaller) contribution from the methyl group to the terminal (delta) CH2 carbon, also through the pi system. Most of the effect of the methyl group is present in the ground-state molecule. There are only relatively small contributions from the methyl group to the ionization energies from redistribution of charge in the pi system in response to the removal of a core electron. In addition to these specific effects, there is an overall decrease in average ionization energy as the size of the molecule increases as well as effects that are specific to the conjugated systems in 1,3-butadiene and 1,3-pentadiene. The results provide insight into the reactivity and regioselectivity of conjugated dienes.
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Affiliation(s)
- T Darrah Thomas
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, USA.
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46
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Maul R, Preuss M, Ortmann F, Hannewald K, Bechstedt F. Electronic excitations of glycine, alanine, and cysteine conformers from first-principles calculations. J Phys Chem A 2007; 111:4370-7. [PMID: 17461555 DOI: 10.1021/jp068294j] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The electronic and optical properties are studied for three conformers of amino acid molecules using gradient-corrected (spin-) density functional theory within a projector-augmented wave scheme and the supercell method. We investigate single-particle excitations such as ionization energies and electron affinities as well as pair excitations. By comparing eigenvalues resulting from several local and nonlocal energy functionals, the influence of treatment of exchange and correlation is demonstrated. The excitations are described within the Delta-self-consistent field method with an occupation number constraint to obtain excitation energies and Stokes shifts. The results are used to also discuss the optical absorption properties. In contrast to the lowest single- and two-particle excitation energies, remarkable changes are found in absorption spectra in dependence on the conformation of the molecule geometry.
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Affiliation(s)
- R Maul
- Institut für Festkörpertheorie und-optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
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47
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Otero E, Urquhart SG. Nitrogen 1s Near-Edge X-ray Absorption Fine Structure Spectroscopy of Amino Acids: Resolving Zwitterionic Effects. J Phys Chem A 2006; 110:12121-8. [PMID: 17078606 DOI: 10.1021/jp064082a] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Considerable variation is observed in the near-edge X-ray absorption fine structure (NEXAFS) spectra of amino acids. To unambiguously characterize the chemical origin of this variation, we have acquired the nitrogen 1s NEXAFS spectra of several amino acids and other model compounds and complemented these experimental measurements with ab initio calculations of isolated molecules and molecular clusters. The systematic differences observed between the zwitterionic and un-ionized forms of amino acids arise directly from the structural difference (-NH2 vs -NH3+), which leads to a change in the degree of Rydberg-valence mixing. Further change arises from quenching of this Rydberg character in the spectra of condensed amino acids. Ab initio calculations are used to explore the degree of Rydberg-valence mixing in the solid state.
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Affiliation(s)
- Edwige Otero
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9, Canada
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48
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Marinho R, Lago A, Homem M, Coutinho L, de Souza G, Naves de Brito A. Gas phase photoabsorption and mass spectra of l-alanine and l-proline in the soft X-ray region. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.10.038] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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49
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Abstract
Ten low-lying conformers of beta-alanine have been studied by the hybrid density functional B3LYP/aug-cc-pVDZ method. Energetic extrapolation calculations at the MP3 and MP4(SDQ) levels of theory and the theoretical photoelectron spectra simulated with the electron propagation theory demonstrate that there are at least three gauche conformers (G1, G2, and G3) in gas-phase experiments. The calculated ionization potentials are in good agreement with the experimental data available in the literature. Natural bond orbital and atoms-in-molecules analyses exhibit a remarkable influence on the molecular electronic structures by the strong intramolecular hydrogen bonding O-H...N in the neutral conformer G2. Remarkable internal rotations of the COOH group are found in the cationic G1+ and G3+ with respect to the neutral conformers. A distonic [NH3+-(CH2)2-COO*] radical can be formed through the spontaneous intramolecular proton transfer in G2+. A novel intramolecular hydrogen bonding, C-H...O, is found in the anti A1+ cation.
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Affiliation(s)
- Shan Xi Tian
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Bond Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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50
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Zhang M, Lin Z. Ab initio studies of the conformers and conformational distribution of the gaseous hydroxyamino acid threonine. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2005.12.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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