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Lu J, Teleanu F, Zou H, Zhang C, Hollingsworth A, Jerschow A. Conformational Landscape of NADH and Ion Binding in Water/DMSO Mixtures via 31P NMR Spectroscopy. J Phys Chem B 2024; 128:8504-8511. [PMID: 39018118 PMCID: PMC11382270 DOI: 10.1021/acs.jpcb.4c03162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/19/2024]
Abstract
This study reports on the conformational states of nicotinamide adenine dinucleotide (NADH) in water/DMSO mixtures and examines the influence of ion binding. We observe evidence of conformational changes through a series of NMR techniques, including 31P NMR relaxation (R1 and R2), chemical exchange saturation transfer (CEST), and diffusion-ordered spectroscopy (DOSY) experiments. The observed variation of the conformational states is indicative of the solvent's influence on NADH's structural flexibility. The experimental findings, in combination with viscosity data, are shown to be in line with findings from earlier molecular dynamics studies. The reported observations emphasize the critical role of the solvent environment in determining the conformational states of NADH and similar molecules with relevance for the biophysiological context. The results found herein can help in studying the biophysical behavior of NADH and similar biomolecules and their associated metabolic pathways under various solvent conditions.
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Affiliation(s)
- Jiaqi Lu
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Florin Teleanu
- Department of Chemistry, New York University, New York, New York 10003, United States
- Interdisciplinary School of Doctoral Studies, University of Bucharest, Bucharest 010041, Romania
- Biophysics and Biomedical Application Laboratory, Extreme Light Infrastructure Nuclear Physics, IFIN-HH, Măgurele 77125, Romania
| | - Huijing Zou
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Chengtong Zhang
- Department of Chemistry, New York University, New York, New York 10003, United States
| | - Andrew Hollingsworth
- Department of Physics, New York University, New York, New York 10003, United States
| | - Alexej Jerschow
- Department of Chemistry, New York University, New York, New York 10003, United States
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2
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Jaiswal VK, Aranda Ruiz D, Petropoulos V, Kabaciński P, Montorsi F, Uboldi L, Ugolini S, Mukamel S, Cerullo G, Garavelli M, Santoro F, Nenov A. Sub-100-fs energy transfer in coenzyme NADH is a coherent process assisted by a charge-transfer state. Nat Commun 2024; 15:4900. [PMID: 38851775 PMCID: PMC11162464 DOI: 10.1038/s41467-024-48871-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 05/15/2024] [Indexed: 06/10/2024] Open
Abstract
Excitation energy transfer (EET) is a key photoinduced process in biological chromophoric assemblies. Here we investigate the factors which can drive EET into efficient ultrafast sub-ps regimes. We demonstrate how a coherent transport of electronic population could facilitate this in water solvated NADH coenzyme and uncover the role of an intermediate dark charge-transfer state. High temporal resolution ultrafast optical spectroscopy gives a 54±11 fs time constant for the EET process. Nonadiabatic quantum dynamical simulations computed through the time-evolution of multidimensional wavepackets suggest that the population transfer is mediated by photoexcited molecular vibrations due to strong coupling between the electronic states. The polar aqueous solvent environment leads to the active participation of a dark charge transfer state, accelerating the vibronically coherent EET process in favorably stacked conformers and solvent cavities. Our work demonstrates how the interplay of structural and environmental factors leads to diverse pathways for the EET process in flexible heterodimers and provides general insights relevant for coherent EET processes in stacked multichromophoric aggregates like DNA strands.
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Affiliation(s)
- Vishal Kumar Jaiswal
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
| | - Daniel Aranda Ruiz
- ICMol, Universidad de Valencia, Catedrático José Beltrán Martínez, 2, 46980, Paterna, Spain
| | - Vasilis Petropoulos
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy
| | - Piotr Kabaciński
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy
| | - Francesco Montorsi
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
| | - Lorenzo Uboldi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy
| | - Simone Ugolini
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
| | - Shaul Mukamel
- Department of Chemistry and Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
| | - Marco Garavelli
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy.
| | - Fabrizio Santoro
- Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area della Ricerca del CNR, Via Moruzzi 1, I-56124, Pisa, Italy
| | - Artur Nenov
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy.
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3
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Reza MM, Durán-Hernández J, González-Cano B, Jara-Cortés J, López-Arteaga R, Cadena-Caicedo A, Muñoz-Rugeles L, Hernández-Trujillo J, Peon J. Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms. J Phys Chem B 2023; 127:8432-8445. [PMID: 37733881 DOI: 10.1021/acs.jpcb.3c03246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
Nicotinamide adenine dinucleotide (NADH) is an important enzyme cofactor with emissive properties that allow it to be used in fluorescence microscopies to study cell metabolism. Its oxidized form NAD+, on the other hand, is considered to produce negligible fluorescence. In this contribution, we describe the photophysics of the isolated nicotinamidic system in both its reduced and oxidized states. This was achieved through the study of model molecules that do not carry the adenine nucleotide since its absorbance would overlap with the absorption spectrum of the nicotinamidic chromophores. We studied three model molecules: nicotinamide (niacinamide, an oxidized form without nitrogen substitution), the oxidized chromophore 1-benzyl-3-carbamoyl-pyridinium bromide (NBzOx), and its reduced form 1-benzyl-1,4-dihydronicotinamide (NBz). For a full understanding of the dynamics, we performed both femtosecond-resolved emission and transient absorption experiments. The oxidized systems, nicotinamide and NBzOx, have similar photophysics, where the originally excited bright state decays on an ultrafast timescale of less than 400 fs. The depopulation of this state is followed by excited-state positive absorption signals, which evolve in two timescales: the first one is from 1 to a few picoseconds and is followed by a second decaying component of 480 ps for nicotinamide in water and of 80-90 ps for nicotinamide in methanol and NBzOx in aqueous solution. The long decay times are assigned as the S1 lifetimes populated from the original higher-lying bright singlet, where this state is nonemissive but can be detected by transient absorption. While for NBzOx in aqueous solution and for nicotinamide in methanol, the S1 signal decays to the solvent-only level, for the aqueous solutions of nicotinamide, a small transient absorption signal remains after the 480 ps decay. This residual signal was assigned to a small population of triplet states formed during the slower S1 decay for nicotinamide in water. The experimental results were complemented by XMS-CASPT2 calculations, which reveal that in the oxidized forms, the rapid evolution of the initial π-π* state is due to a direct crossing with lower-energy dark n-π* singlet states. This coincides with the experimental observation of long-lived nonemissive states (80 to 480 ps depending on the system). On the other hand, the reduced model compound NBz has a long-lived emissive π-π* S1 state, which decays with a 510 ps time constant, similarly to the parent compound NADH. This is consistent with the XMS-CASPT2 calculations, which show that for the reduced chromophore, the dark states lie at higher energies than the bright π-π* S1 state.
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Affiliation(s)
- Mariana M Reza
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Durán-Hernández
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Beatriz González-Cano
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Jara-Cortés
- Unidad Académica de Ciencias Básicas e Ingenierías, Universidad Autónoma de Nayarit, Tepic 63155, México
| | - Rafael López-Arteaga
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Andrea Cadena-Caicedo
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Leonardo Muñoz-Rugeles
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
| | - Jesús Hernández-Trujillo
- Departamento de Física y Química Teórica, Facultad de Química, UNAM, Ciudad de México 04510, México
| | - Jorge Peon
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México 04510, México
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Abstract
Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.
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Affiliation(s)
- Erick L Bastos
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Frank H Quina
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
- Department of Chemical Engineering, Polytechnic School, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Maurício S Baptista
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
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Li H, Cao S, Chen J, Zhang S, Xu J, Knutson JR. Ultrafast fluorescence dynamics of NADH in aprotic solvents: Quasi-static self-quenching unmasked. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2022.114384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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6
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Smolin AG. Ab Initio Studies of NMNH(2-) Conformers in Water-Methanol Solutions: Comparative Analysis of the Biexponential Fluorescence Signals for NMNH(2-) and NADH. J Phys Chem B 2022; 126:10870-10881. [PMID: 36524597 DOI: 10.1021/acs.jpcb.2c08220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ab initio studies of the structure of reduced β-nicotinamide d-ribonucleotide (NMNH(2-)) conformations in water and methanol solutions have been carried out for clarifying the role of the phosphate groups in fluorescence parameters of the NMNH(2-) molecule and the reduced β-nicotinamide adenine dinucleotide (NADH) molecule. Relaxed potential energy surfaces as a function of the dihedral rotation angle of the amide group in the NMNH(2-) molecule were calculated in the ground electronic state and the first excited electronic state to better understand the effect of phosphate groups on the nonradiative decay rates in the nicotinamide chromophore groups. The differences in the weighting coefficients in the biexponential fluorescence signals for NMNH(2-) and NADH molecules in solution were explained. A strong hydrogen bonding between the amide hydrogen atom and the nearest oxygen O- atom from the phosphate group was detected by ab initio calculations for the folded NMNH(2-) conformations in the ground electronic state at trans configurations of the nicotinamide ring. This hydrogen bonding turned out to be much weaker for the first excited electronic state. These calculated data show that, after optical excitation of the NMNH(2-) molecule, a rapid change in the geometry of the molecule is possible. The strong interaction of the phosphate group with the amide group in NMNH(2-) molecules in aqueous solution leads to the predominance of the folded NMNH(2-) conformations and trans configurations of the nicotinamide ring. This explains the reason for the dominance of one fluorescence decay time of NMNH(2-) in the aqueous solution. Based on these data, an important conclusion can be drawn that the contribution of the exponent with the short decay time τ ≈ 0.28 ns to the fluorescence signal of NMNH(2-), NADH, and NADPH molecules is related to the trans configuration of the nicotinamide ring.
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Affiliation(s)
- Andrey G Smolin
- Ioffe Institute, Politekhnicheskaya 26, 194021Saint Petersburg, Russia
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7
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Determination of fluorescence quantum yields and decay times of NADH and FAD in water-alcohol mixtures: The analysis of radiative and nonradiative relaxation pathways. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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8
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Buckley DP, Migaud ME, Tanner JJ. Conformational Preferences of Pyridone Adenine Dinucleotides from Molecular Dynamics Simulations. Int J Mol Sci 2022; 23:11866. [PMID: 36233167 PMCID: PMC9570408 DOI: 10.3390/ijms231911866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 09/23/2022] [Accepted: 10/01/2022] [Indexed: 11/25/2022] Open
Abstract
Pyridone adenine dinucleotides (ox-NADs) are redox inactive derivatives of the enzyme cofactor and substrate nicotinamide adenine dinucleotide (NAD) that have a carbonyl group at the C2, C4, or C6 positions of the nicotinamide ring. These aberrant cofactor analogs accumulate in cells under stress and are potential inhibitors of enzymes that use NAD(H). We studied the conformational landscape of ox-NADs in solution using molecular dynamics simulations. Compared to NAD+ and NADH, 2-ox-NAD and 4-ox-NAD have an enhanced propensity for adopting the anti conformation of the pyridone ribose group, whereas 6-ox-NAD exhibits greater syn potential. Consequently, 2-ox-NAD and 4-ox-NAD have increased preference for folding into compact conformations, whereas 6-ox-NAD is more extended. ox-NADs have distinctive preferences for the orientation of the pyridone amide group, which are driven by intramolecular hydrogen bonding and steric interactions. These conformational preferences are compared to those of protein-bound NAD(H). Our results may help in identifying enzymes targeted by ox-NADs.
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Affiliation(s)
- David P. Buckley
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Marie E. Migaud
- Mitchell Cancer Institute, Department of Pharmacology, College of Medicine, University of South Alabama, Mobile, AL 36604, USA
| | - John J. Tanner
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
- Department of Chemistry, University of Missouri, Columbia, MO 65211, USA
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9
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Heidelman M, Dhakal B, Gikunda M, Silva KPT, Risal L, Rodriguez AI, Abe F, Urayama P. Cellular NADH and NADPH Conformation as a Real-Time Fluorescence-Based Metabolic Indicator under Pressurized Conditions. Molecules 2021; 26:5020. [PMID: 34443607 PMCID: PMC8402201 DOI: 10.3390/molecules26165020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/15/2021] [Accepted: 08/16/2021] [Indexed: 11/25/2022] Open
Abstract
Cellular conformation of reduced pyridine nucleotides NADH and NADPH sensed using autofluorescence spectroscopy is presented as a real-time metabolic indicator under pressurized conditions. The approach provides information on the role of pressure in energy metabolism and antioxidant defense with applications in agriculture and food technologies. Here, we use spectral phasor analysis on UV-excited autofluorescence from Saccharomyces cerevisiae (baker's yeast) to assess the involvement of one or multiple NADH- or NADPH-linked pathways based on the presence of two-component spectral behavior during a metabolic response. To demonstrate metabolic monitoring under pressure, we first present the autofluorescence response to cyanide (a respiratory inhibitor) at 32 MPa. Although ambient and high-pressure responses remain similar, pressure itself also induces a response that is consistent with a change in cellular redox state and ROS production. Next, as an example of an autofluorescence response altered by pressurization, we investigate the response to ethanol at ambient, 12 MPa, and 30 MPa pressure. Ethanol (another respiratory inhibitor) and cyanide induce similar responses at ambient pressure. The onset of non-two-component spectral behavior upon pressurization suggests a change in the mechanism of ethanol action. Overall, results point to new avenues of investigation in piezophysiology by providing a way of visualizing metabolism and mitochondrial function under pressurized conditions.
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Affiliation(s)
- Martin Heidelman
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Bibek Dhakal
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Millicent Gikunda
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Kalinga Pavan Thushara Silva
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Laxmi Risal
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Andrew I. Rodriguez
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
| | - Fumiyoshi Abe
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara 252-5258, Japan;
| | - Paul Urayama
- Department of Physics, Miami University, Oxford, OH 45056, USA; (M.H.); (B.D.); (M.G.); (K.P.T.S.); (L.R.); (A.I.R.)
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Gorbunova IA, Sasin ME, Beltukov YM, Semenov AA, Vasyutinskii OS. Anisotropic relaxation in NADH excited states studied by polarization-modulation pump-probe transient spectroscopy. Phys Chem Chem Phys 2020; 22:18155-18168. [PMID: 32766648 DOI: 10.1039/d0cp02496a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We present the results of experimental and theoretical studies of fast anisotropic relaxation and rotational diffusion in the first electron excited state of biological coenzyme NADH in water-ethanol solutions. The experiments have been carried out by means of a novel polarization-modulation transient method and fluorescence polarization spectroscopy. For interpretation of the experimental results a model of the anisotropic relaxation in terms of scalar and vector properties of transition dipole moments has been developed based on the Born-Oppenheimer approximation. This model allows for the description of fast isotropic and anisotropic excited state relaxation under excitation of molecules by ultrafast laser pulses in transient absorption and upconversion experiments. The results obtained suggest that the dynamics of anisotropic rovibronic relaxation in NADH under excitation with 100 fs pump laser pulses can be characterised by a single vibrational relaxation time τv lying in the range of 2-15 ps and a single rotation diffusion time τr lying in the range of 100-450 ps, both depending on ethanol concentration. The dependence of the times τv and τr on the solution polarity (static permittivity) and viscosity has been determined and analyzed. Limiting values of the term P2(cos θ) describing the rotation of the transition dipole moment in the course of vibrational relaxation have been determined from experiments as a function of ethanol concentration and analyzed.
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Affiliation(s)
| | - Maxim E Sasin
- Ioffe Institute, Polytekhnicheskaya 26, St. Petersburg, Russia.
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Gorbunova IA, Sasin ME, Rubayo-Soneira J, Smolin AG, Vasyutinskii OS. Two-Photon Excited Fluorescence Dynamics in NADH in Water-Methanol Solutions: The Role of Conformation States. J Phys Chem B 2020; 124:10682-10697. [PMID: 33175534 DOI: 10.1021/acs.jpcb.0c07620] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dynamics of polarized fluorescence in reduced nicotinamide adenine dinucleotide (NADH) at 460 nm under two-photon excitation at 720 nm by femtosecond laser pulses in water-methanol solutions has been studied experimentally and theoretically as a function of methanol concentration. A number of fluorescence parameters have been determined from experiment by means of the global fit procedure and then compared with the results reported by other authors. A comprehensive analysis of experimental errors was made. Ab initio calculations of the structure of NADH in water and methanol and of β-nicotinamide mononucleotide (NMNH) in vacuum have been carried out for clarifying the role of decay time heterogeneity. The main results obtained are as follows. An explanation of the heterogeneity in the measured fluorescence decay times in NADH has been suggested based on the influence of the internal molecular electric field in the nicotinamide ring on nonradiative decay rates. We suggest that different charge distributions in the cis and trans configurations result in different internal electrostatic field distributions that lead to the decay time heterogeneity. A slight but noticeable rise of the fluorescence decay times τ1 and τ2 with methanol concentration was observed and treated as a minor effect of a nonradiative relaxation slowing due to the decrease in solution polarity. Relative concentrations of the folded and unfolded NADH conformations in solutions have been determined using a new method of analysis of the rotational diffusion time τr as a function of methanol concentration on the basis of the Stokes-Einstein-Debye equation. The analysis of the fluorescence anisotropy parameters obtained under linearly and circularly polarized excitation and the parameter Ω has been carried out and resulted in the determination of the two-photon excitation tensor components and suggested the existence of two excitation channels with comparable intensities. These were the longitudinal excitation channel dominated by the diagonal tensor component Szz and the mixed excitation channel dominated by the off-diagonal tensor components |Sxz2 + Syz2|1/2.
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Affiliation(s)
| | - Maxim E Sasin
- Ioffe Institute, 26 Polytekhnicheskaya, St.Petersburg 194021, Russia
| | - Jesus Rubayo-Soneira
- Universidad de La Habana, Instituto Superior de Tecnologías y Ciencias Aplicadas, La Habana 10400, Cuba
| | - Andrey G Smolin
- Ioffe Institute, 26 Polytekhnicheskaya, St.Petersburg 194021, Russia
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