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Schneiker A, Góbi S, Joshi PR, Bazsó G, Lee YP, Tarczay G. Non-energetic, Low-Temperature Formation of C α-Glycyl Radical, a Potential Interstellar Precursor of Natural Amino Acids. J Phys Chem Lett 2021; 12:6744-6751. [PMID: 34264091 DOI: 10.1021/acs.jpclett.1c01306] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The reaction of H atoms with glycine was investigated at 3.1 K in para-H2, a quantum-solid host. The reaction was followed by IR spectroscopy, with the spectral analysis aided by quantum chemical computations. Comparison of the experimental IR spectrum with computed anharmonic frequencies and intensities proved that, regardless of the reactant glycine conformation, Cα-glycyl radical is formed in an H-atom-abstraction process with great selectivity. The product of the second H-atom abstraction, iminoacetic acid, was also observed in a smaller amount. The Cα-glycyl radical is sensitive to UV light and decomposes to iminoacetic acid and H atom upon 280 nm radiation. Since the reactive radical center is located on the Cα-atom, it is suggested that natural α-amino acids can be formed from glycine via the Cα-glycyl radical by non-energetic mechanisms in the solid phase of the interstellar medium.
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Affiliation(s)
- Anita Schneiker
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
| | - Sándor Góbi
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
| | - Prasad Ramesh Joshi
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
| | - Gábor Bazsó
- Wigner Research Centre for Physics, P. O. Box 49, H-1525 Budapest, Hungary
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
- Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 300093, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106319, Taiwan
| | - György Tarczay
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
- Laboratory of Molecular Spectroscopy, Institute of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest, Hungary
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Sosnovsky DV, Morozova OB, Yurkovskaya AV, Ivanov KL. Relation between CIDNP formed upon geminate and bulk recombination of radical pairs. J Chem Phys 2017; 147:024303. [DOI: 10.1063/1.4986243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Denis V. Sosnovsky
- International Tomography Center, Siberian Branch of the Russian Academy of Science, Novosibirsk 630090, Russia and Novosibirsk State University, Novosibirsk 630090, Russia
| | - Olga B. Morozova
- International Tomography Center, Siberian Branch of the Russian Academy of Science, Novosibirsk 630090, Russia and Novosibirsk State University, Novosibirsk 630090, Russia
| | - Alexandra V. Yurkovskaya
- International Tomography Center, Siberian Branch of the Russian Academy of Science, Novosibirsk 630090, Russia and Novosibirsk State University, Novosibirsk 630090, Russia
| | - Konstantin L. Ivanov
- International Tomography Center, Siberian Branch of the Russian Academy of Science, Novosibirsk 630090, Russia and Novosibirsk State University, Novosibirsk 630090, Russia
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Morozova OB, Yurkovskaya AV. Aminium Cation Radical of Glycylglycine and its Deprotonation to Aminyl Radical in Aqueous Solution. J Phys Chem B 2008; 112:12859-62. [DOI: 10.1021/jp807149a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Olga B. Morozova
- International Tomography Center of SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia, and Institute of Experimental Physics, Free University of Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Alexandra V. Yurkovskaya
- International Tomography Center of SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia, and Institute of Experimental Physics, Free University of Berlin, Arnimallee 14, 14195 Berlin, Germany
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Lebedeva NV, Gorelik EV, Prowatzke AM, Forbes MDE. Model systems for poly(acrylic acid) main-chain radicals based on the Kemp's triacid framework. J Phys Chem B 2008; 112:7574-80. [PMID: 18517241 DOI: 10.1021/jp712098j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kemp's triacid (KTA) and cyclohexane tricarboxylic acid (CTA) are small-molecule model systems for acrylic acid polymers, having the same functionalities and stereoregularities as isotactic poly(methacrylic acid) (PMAA) and poly(acrylic acid) (PAA), respectively. As part of an ongoing investigation of radicals produced by photolysis of acrylic polymers, the photochemistry and free radicals from the model systems have been studied using time-resolved EPR spectroscopy as a function of temperature and pH. Radicals are created by direct photolysis of the acids at 248 nm or by sensitized photo-oxidation using quinone triplet states at 308 nm. The two methods of radical production lead to different chemically induced electron spin polarization (CIDEP) patterns in the ensuing radicals, which are simulated and discussed. Well-resolved spectra are obtained at all temperatures for the model system radicals, which are determined to be in the slow motion condition. DFT calculations of the model system radicals are presented and discussed in support of the experimental data.
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Affiliation(s)
- Natalia V Lebedeva
- Caudill Laboratories, CB # 3290, Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Tarabek P, Bonifacić M, Beckert D. Time-resolved FT EPR and optical spectroscopy study on photooxidation of aliphatic alpha-amino acids in aqueous solutions; electron transfer from amino vs carboxylate functional group. J Phys Chem A 2007; 110:7293-302. [PMID: 16737283 DOI: 10.1021/jp060764m] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Using time-resolved Fourier transform electron paramagnetic resonance, FT EPR, and optical spectroscopy, the photooxidation of glycine, alpha-alanine, alpha-aminoisobutyric acid, and model compounds beta-alanine, methylamine and sodium acetate, by excited triplets of anthraquinone-2,6-disulfonate dianion was studied in aqueous solutions in the pH range 5-13. Anthraquinone radical trianions showing strong emissive spin-polarization (CIDEP) were formed, indicating fast electron transfer from the quenchers to the spin-polarized quinone triplet as the primary reaction. None of the primary radicals formed upon one-electron oxidation of quenchers could be detected at the nanosecond time scale of FT EPR measurements because of their very fast transformation into secondary products. The latter were identified to be decarboxylated alpha-aminoalkyl radicals for alpha-amino acids anions and zwitterions, beta-aminoalkyl radicals for beta-alanine zwitterions, and methyl radicals for acetate anions; corresponding aminyl radicals were the first EPR detectable products from beta-alanine anions and methylamine. Thus, anthraquinone-2,6-disulfonate triplet can take an electron from both NH(2)- and -CO(2)(-) functional groups forming aminium ((+*)NH(2)-) and acyloxyl (-CO(2)(*)) radicals, respectively. Aminium radicals derived from beta-alanine anions and CH(3)-NH(2) stabilize by deprotonation into aminyl radicals, whereas these derived from alpha-amino acids anions are known to suffer ultrafast decarboxylation (tau approximately 10 ps). Analysis of the polarization patterns revealed that decarboxylation from acyloxyl radicals are considerably slower (ns < tau < 0.1 micros). Therefore, in the case of alpha-amino acids, the isoelectronic structures NH(2)-CR(2)-CO(2)(*) and (+*)NH(2)-CR(2)-CO(2)(-) probably do not constitute resonance mesomeric forms of one and the same species and the decarboxylation of aminium radicals is not preceded by the intramolecular carboxylate to amino group electron transfer. Absolute triplet quenching rate constants at zero ionic strength were in the range of 2 x 10(8) to 2 x 10(9) M(-1) s(-1) for R-NH(2) and 2 x 10(7) to 10(8) M(-1) s(-1) for R-CO(2)(-) type of electron donors, reflecting in principle their standard reduction potentials. The strengths of acids: (+)NH(3)-(*)CH(2), (+)NH(3)-(*)C(CH(3))H, and (+)NH(3)-(*)C(CH(3))(2), pK(a) <4, >6, and >7, respectively, were found to be remarkably strongly dependent on alpha-C substitution. The conjugate bases of these alpha-aminoalkyl radicals reduce anthraquinone-2,6-disulfonate dianion ground state with k(sec) = 3 x 10(9) M(-1) s(-1).
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Affiliation(s)
- Peter Tarabek
- Interdisciplinary Research Group Time-Resolved Spectroscopy, Faculty of Chemistry and Mineralogy, University of Leipzig, Germany
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Görner H. Electron transfer from aromatic amino acids to triplet quinones. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2007; 88:83-9. [PMID: 17604179 DOI: 10.1016/j.jphotobiol.2007.05.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Revised: 05/03/2007] [Accepted: 05/03/2007] [Indexed: 10/23/2022]
Abstract
The photoreduction of 1,4-benzoquinone, 1,4-naphthoquinone, 9,10-anthraquinone (AQ) and several methylated or halogenated derivatives in argon-saturated acetonitrile-water mixtures by indole, N-acetyltryptophan and N-acetyltyrosine was studied by time-resolved UV-vis spectroscopy using 20 ns UV laser pulses. The quinone triplet state is quenched by the aromatic amino acids and the rate constants are (1-5)x10(9)M(-1)s(-1). The semiquinone radical anion Q.(-) is the major observable transient after electron transfer from amino acids to the quinone triplet state. Termination of Q.(-) and amino acid derived radicals takes place in the mus-ms range. The effects of structure and other specific properties of quinones and amino acids are discussed. The radicals are subjects of intercept with oxygen, whereby hydrogen peroxide is eventually formed. The quantum yield of oxygen uptake Phi(-O2) as a measure of formation of hydrogen peroxide increases with increasing amino acid concentration, approaching Phi(-O2) for AQ in air-saturated solution.
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Affiliation(s)
- Helmut Görner
- Max-Planck-Institut für Bioanorganische Chemie, D-45413 Mülheim an der Ruhr, Germany.
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White RC, Gorelik V, Bagryanskaya EG, Forbes MDE. Photoredox chemistry of AOT: electron transfer and hydrogen abstraction in microemulsions involving the surfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:4183-91. [PMID: 17343399 DOI: 10.1021/la063322a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Time-resolved magnetic resonance experiments (TREPR and CIDNP) are used to investigate previously unobserved redox chemistry of the surfactant dioctyl sulfosuccinate ester (AOT) using the photoexcited triplet state of anthraquinone 2,6-disulfonate (3AQDS*). Several different free radicals resulting from two independent oxidation pathways (electron transfer and hydrogen abstraction) are observed. These include the radical ions of AQDS and sulfite from electron-transfer processes, carbon-centered radicals from H-atom abstraction reactions, and an additional carbon-centered radical formed by electron transfer from the AOT sulfonate head group followed by the loss of SO3. The radicals exhibit intense chemically induced dynamic electron spin polarization (CIDEP) in their TREPR spectra. The intensity ratios of the observed TREPR signals for each radical depend on the water pool size and temperature, which in turn affect the predominant CIDEP mechanism. All signal carriers are accounted for by simulation, and CIDNP results provide strong supporting evidence for the assignments.
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Affiliation(s)
- Ryan C White
- Caudill Laboratories, CB#3290, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Yashiro H, White RC, Yurkovskaya AV, Forbes MDE. Methionine Radical Cation: Structural Studies as a Function of pH Using X- and Q-Band Time-Resolved Electron Paramagnetic Resonance Spectroscopy. J Phys Chem A 2005; 109:5855-64. [PMID: 16833920 DOI: 10.1021/jp051551k] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A comprehensive high resolution electron paramagnetic resonance (EPR) characterization of the l-methionine radical cation and its N-acetyl derivative in liquid solution at room temperature is presented. The cations were generated photochemically in high yield by excimer laser excitation of a water soluble dye, anthraquinone sulfonate sodium salt, the excited triplet state of which is quenched by electron transfer from the side chain sulfur atom of methionine or N-acetylmethionine. The radicals were detected by continuous wave (CW) time-resolved electron paramagnetic resonance (TREPR) spectroscopy at X-band (9.5 GHz) and Q-band (35 GHz) microwave frequencies. At pH values well below the pK(a) of the protonated amine nitrogen, the cation forms a dimer with another ground-state methionine molecule through a S-S three-electron bond. In basic solution, the lone pair on the nitrogen of the amino acid is available to make an intramolecular S-N three-electron bond with the side chain sulfur atom, leading to a five-membered ring structure for the cation. When the amino acid nitrogen is unsubstituted (methionine itself), rapid deprotonation to an aminyl radical takes place at high pH values. If the nitrogen is substituted (N-acetylmethionine), the cyclic structure is observed within its electron spin relaxation time at about 1 micros. Spectral simulation provides chemical shifts (g-factors) and hyperfine coupling constants for all structures, and isotopic labeling experiments strongly support the assignments.
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Affiliation(s)
- Haruhiko Yashiro
- Venable and Kenan Laboratories, Department of Chemistry, CB#3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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White RC, Tarasov VF, Forbes MDE. Photooxidation of diglycine in confined media. Application of the microreactor model for spin-correlated radical pairs in reverse micelles and water-in-oil microemulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:2721-2727. [PMID: 15779940 DOI: 10.1021/la047382x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Time-resolved electron paramagnetic resonance spectra (X-band) of correlated radical pairs created in AOT reverse micelles and microemulsions are presented, simulated, and discussed using the microreactor model. The radicals are formed inside the water pool using photooxidation of diglycine by the excited triplet states of two different anthraquinone sulfonate salts. Water pool size and temperature effects on the spectra are reported, and the simulations allow for extraction of the diffusion coefficient in the interior, which monotonically increases with water pool size. The data directly correlate with the diffusional properties of correlated radical pairs in regular aqueous micelle solutions studied previously by similar methods. Competition between H-atom abstraction and electron transfer is observed with anthraquinone sulfonate, but electron transfer is the only reaction pathway observed when anthraquinone disulfonate triplet state is the sensitizing species.
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Affiliation(s)
- Ryan C White
- Venable and Kenan Laboratories, Department of Chemistry, CB #3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Tarábek P, Bonifačić M, Beckert D. Photooxidation of Glycylglycine. Two-Channel Reaction Mechanism as Studied by Time-Resolved FT EPR. J Phys Chem A 2004. [DOI: 10.1021/jp037779u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peter Tarábek
- Interdisciplinary Research Group “Time-Resolved Spectroscopy”, Faculty of Chemistry and Mineralogy, University of Leipzig, Permoserstrasse 15, Leipzig, D-04318 Germany, and Department of Physical Chemistry, Rud̄er Bošković Institute, Bijenička c. 54, HR-10 000 Zagreb, Croatia
| | - Marija Bonifačić
- Interdisciplinary Research Group “Time-Resolved Spectroscopy”, Faculty of Chemistry and Mineralogy, University of Leipzig, Permoserstrasse 15, Leipzig, D-04318 Germany, and Department of Physical Chemistry, Rud̄er Bošković Institute, Bijenička c. 54, HR-10 000 Zagreb, Croatia
| | - Dieter Beckert
- Interdisciplinary Research Group “Time-Resolved Spectroscopy”, Faculty of Chemistry and Mineralogy, University of Leipzig, Permoserstrasse 15, Leipzig, D-04318 Germany, and Department of Physical Chemistry, Rud̄er Bošković Institute, Bijenička c. 54, HR-10 000 Zagreb, Croatia
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