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Lamas I, González J, Longarte A, Montero R. Influence of H-bonds on the photoionization of aromatic chromophores in water: The aniline molecule. J Chem Phys 2023; 158:2890456. [PMID: 37184001 DOI: 10.1063/5.0147503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 05/01/2023] [Indexed: 05/16/2023] Open
Abstract
We have conducted time-resolved experiments (pump-probe and pump-repump-probe) on a model aromatic chromophore, aniline, after excitation in water at 267 nm. In the initial spectra recorded, in addition to the absorption corresponding to the bright ππ* excitation, the fingerprint of a transient state with the electron located on the solvent molecule is identified. We postulate that the latter corresponds to the πσ* state along the N-H bond, whose complete relaxation with a ∼500 ps lifetime results in the formation of the fully solvated electron and cation. This ionization process occurs in parallel with the ππ* photophysical channel that yields the characteristic ∼1 ns fluorescence lifetime. The observed branched pathway is rationalized in terms of the different H-bonds that the water establishes with the amino group. The proposed mechanism could be common for aromatics in water containing N-H or O-H bonds and would allow the formation of separated charges after excitation at the threshold of their electronic absorptions.
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Affiliation(s)
- Iker Lamas
- Facultad de Ciencia y Tecnología, Departamento de Química Física, Universidad del País Vasco (UPV/EHU), Apart. 644, 48080 Bilbao, Spain
| | - Jorge González
- Facultad de Ciencia y Tecnología, Departamento de Química Física, Universidad del País Vasco (UPV/EHU), Apart. 644, 48080 Bilbao, Spain
| | - Asier Longarte
- Facultad de Ciencia y Tecnología, Departamento de Química Física, Universidad del País Vasco (UPV/EHU), Apart. 644, 48080 Bilbao, Spain
| | - Raúl Montero
- Facultad de Ciencia y Tecnología, SGIKER Laser Facility, UPV/EHU, Sarriena, S/N, 48940 Leioa, Spain
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Synthesis of silver nanoparticles and its contribution to the capability of Bacillus subtilis to deal with polluted waters. Appl Microbiol Biotechnol 2019; 103:6319-6332. [DOI: 10.1007/s00253-019-09880-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 04/15/2019] [Accepted: 04/24/2019] [Indexed: 11/27/2022]
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Zhang X, Yang CW, Yu HQ, Sheng GP. Light-induced reduction of silver ions to silver nanoparticles in aquatic environments by microbial extracellular polymeric substances (EPS). WATER RESEARCH 2016; 106:242-248. [PMID: 27728818 DOI: 10.1016/j.watres.2016.10.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/30/2016] [Accepted: 10/01/2016] [Indexed: 06/06/2023]
Abstract
Microbial extracellular polymeric substances (EPS) widely exist in natural environments and affect the migration and transformation of pollutants in aquatic environments. Previous works report that EPS have some reducing functional groups and can reduce heavy metals. However, because of the weak reducing capability of EPS, the reduction of heavy metals by EPS without cells is extremely slow, and its effect on heavy metals species is insignificant. In this work, the accelerated reduction of silver ions (Ag+) by EPS from Shewanella oneidensis MR-1 under illumination was investigated. UV-visible spectroscopy, transmission electron microscopy (TEM) coupled with an energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to confirm the formation of silver nanoparticles (AgNPs) via the reduction of Ag+ by EPS under light illumination. The Ag+ reduction by EPS follows pseudo-first-order kinetics under both visible and UV light, and the light irradiation can significantly accelerate AgNPs formation. On the one hand, visible light can excite AgNPs for their surface plasma resonance (SPR) and accelerate the electrons from the EPS to adjacent Ag+. On the other hand, EPS molecules may be excited by UV light to produce strong reducing species, which enhance Ag+ reduction. Moreover, pH, dissolved oxygen were found to affect the formation of AgNPs by EPS. This work proves the reducing capability of EPS on the reduction of Ag+, and this process can be accelerated under light illumination, which may affect the speciation and transformation of heavy metals in natural waters.
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Affiliation(s)
- Xin Zhang
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Chuan-Wang Yang
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Han-Qing Yu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Guo-Ping Sheng
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
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Sengupta B, Mukherjee P, Das S, Rafiq S, Gupta S, Dethe DH, Sen P. Femtosecond dynamics of photoinduced cis-trans isomerization of ethyl-3-(1H-indole-3-yl)acrylate. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.08.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Janssen EML, Erickson PR, McNeill K. Dual roles of dissolved organic matter as sensitizer and quencher in the photooxidation of tryptophan. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:4916-24. [PMID: 24708197 DOI: 10.1021/es500535a] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The photooxidation processes of tryptophan (Trp) in the presence of dissolved organic matter (DOM) were identified and quantified by steady-state photolysis experiments, laser spectroscopy and kinetic modeling. In sunlight, Trp photooxidation is dominated by the reaction with excited triplet DOM ((3)DOM), accounting for approximately 50-70% of the total degradation, depending on the DOM concentration and source. Reaction with singlet oxygen and direct photolysis are secondary processes that are both still more important than the reaction with hydroxyl radical. Both direct photolysis and reaction with (3)DOM form Trp radical cation (Trp(•+)) via Trp photoionization and direct oxidation, respectively. The Trp(•+) can be converted back to Trp by suitable electron or hydrogen atom donors. Transient absorption spectroscopy shows that DOM itself and low-molecular-weight analogues of redox-active moieties can reduce the lifetime of photochemically produced Trp(•+) and thus quench Trp degradation. This study demonstrates that DOM plays dual roles in the photodegradation of Trp acting as a sensitizer and quencher. The photochemistry of Trp and the participation of DOM have direct implications for photochemical reactions in extracellular proteins as well as for organic compounds in aquatic systems with similar photoionization processes.
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Affiliation(s)
- Elisabeth M-L Janssen
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich , CH-8092, Zurich, Switzerland
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Steinmann D, Ji JA, Wang YJ, Schöneich C. Photodegradation of human growth hormone: a novel backbone cleavage between Glu-88 and Pro-89. Mol Pharm 2013; 10:2693-706. [PMID: 23721578 DOI: 10.1021/mp400128j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The exposure of protein pharmaceuticals to light can cause loss of potency, oxidation, structural changes and aggregation. To elucidate the chemical pathways of photodegradation, we irradiated human growth hormone (hGH) at λ = 254 nm, λ ≈ 265-340 nm, and λ ≈ 295-340 nm (using the spectral cutoff of borosilicate glass) and analyzed the products by mass spectrometry. By means of LC-MS/MS analysis, we observed an unusual peptide backbone cleavage between Glu-88 and Pro-89. The crystal structure of hGH indicates that these residues are in proximity to Trp-86, which likely mediates this backbone cleavage. The two cleavage fragments observed by MS/MS analysis indicate the loss of CO from the amide bond and replacement of the Glu-C(═ O)Pro bond with a Glu-H bond, accompanied by double bond formation on proline. The reaction is oxygen-independent and likely involves hydrogen transfer to the Cα of Glu-88. To probe the influence of the protein fold, we irradiated hGH in its unfolded state, in 1:1 (v/v) acetonitrile/water, and also the isolated tryptic peptide Ile-78-Arg-90, which contains the Glu-88-Pro-89 sequence. In both cases, the cleavage between Glu-88 and Pro-89 was largely suppressed, while other cleavage pathways became dominant, notably between Gln-84 and Ser-85, as well as Ser-85 and Trp-86.
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Affiliation(s)
- Daniel Steinmann
- Department of Pharmaceutical Chemistry, University of Kansas , Lawrence, Kansas 66047, United States
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Huijser A, Rode MF, Corani A, Sobolewski AL, Sundström V. Photophysics of indole-2-carboxylic acid in an aqueous environment studied by fluorescence spectroscopy in combination with ab initio calculations. Phys Chem Chem Phys 2012; 14:2078-86. [DOI: 10.1039/c2cp22958g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Correia M, Neves-Petersen MT, Parracino A, di Gennaro AK, Petersen SB. Photophysics, photochemistry and energetics of UV light induced disulphide bridge disruption in apo-α-lactalbumin. J Fluoresc 2011; 22:323-37. [PMID: 21997288 DOI: 10.1007/s10895-011-0963-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 08/30/2011] [Indexed: 11/29/2022]
Abstract
Continuous 295 nm excitation of whey protein bovine apo-α-lactalbumin (apo-bLA) results in an increase of tryptophan fluorescence emission intensity, in a progressive red-shift of tryptophan fluorescence emission, and breakage of disulphide bridges (SS), yielding free thiol groups. The increase in fluorescence emission intensity upon continuous UV-excitation is correlated with the increase in concentration of free thiol groups in apo-bLA. UV-excitation and consequent SS breakage induce conformational changes on apo-bLA molecules, which after prolonged illumination display molten globule spectral features. The rate of tryptophan fluorescence emission intensity increase at 340 nm with excitation time increases with temperature in the interval 9.3-29.9°C. The temperature-dependent 340 nm emission kinetic traces were fitted by a 1st order reaction model. Native apo-bLA molecules with intact SS bonds and low tryptophan emission intensity are gradually converted upon excitation into apo-bLA molecules with disrupted SS, molten-globule-like conformation, high tryptophan emission intensity and red-shifted tryptophan emission. Experimental Ahrrenius activation energy was 21.8 ± 2.3 kJ x mol(-1). Data suggests that tryptophan photoionization from the S(1) state is the likely pathway leading to photolysis of SS in apo-bLA. Photoionization mechanism(s) of tryptophan in proteins and in solution and the activation energy of tryptophan photoionization from S(1) leading to SS disruption in proteins are discussed. The observations present in this paper raise concern regarding UV-light pasteurization of milk products. Though UV-light pasteurization is a faster and cheaper method than traditional thermal denaturation, it may also lead to loss of structure and functionality of milk proteins.
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Affiliation(s)
- Manuel Correia
- Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, DK-9220, Aalborg, Denmark.
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Gregersen JA, Tureček F. Mass-spectrometric and computational study of tryptophan radicals (Trp + H)˙ produced by collisional electron transfer to protonated tryptophan in the gas phase. Phys Chem Chem Phys 2010; 12:13434-47. [DOI: 10.1039/c0cp00597e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Sobolewski AL, Domcke W. Computational studies of the photophysics of hydrogen-bonded molecular systems. J Phys Chem A 2007; 111:11725-35. [PMID: 17941621 DOI: 10.1021/jp075803o] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The role of electron- and proton-transfer processes in the photophysics of hydrogen-bonded molecular systems has been investigated with ab initio electronic-structure calculations. Adopting indole, pyridine, and ammonia as molecular building blocks, we discuss generic mechanisms of the photophysics of isolated aromatic chromophores (indole), complexes of pi systems with solvent molecules (indole-ammonia, pyridine-ammonia), hydrogen-bonded aromatic pairs (indole-pyridine), and intramolecularly hydrogen-bonded pi systems (7-(2'-pyridyl)indole). The reaction mechanisms are discussed in terms of excited-state minimum-energy paths, conical intersections, and the properties of frontier orbitals. A common feature of the photochemistry of the various systems is the electron-driven proton-transfer (EDPT) mechanism: highly polar charge-transfer states of 1pipi*, 1npi*, or 1pisigma* character drive the proton transfer, which leads, in most cases, to a conical intersection of the S1 and S0 surfaces and thus ultrafast internal conversion. In intramolecularly hydrogen-bonded aromatic systems, out-of-plane torsion is additionally needed for barrierless access to the S1-S0 conical intersection. The EDPT process plays an essential role in diverse photophysical phenomena, such as fluorescence quenching in protic solvents, the function of organic photostabilizers, and the photostability of biological molecules.
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