Ultrafast fluorescence dynamics of NADH in aprotic solvents: Quasi-static self-quenching unmasked

Li, Haoyang; Cao, Simin; Chen, Jinquan; Zhang, Sanjun; Xu, Jianhua; Knutson, Jay R.

doi:10.1016/j.jphotochem.2022.114384

Cited by 2 publications

(2 citation statements)

References 48 publications

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“…The time constants related to this shift are around 7 ps (Table S1). From such timescale and considering that 380 nm corresponds to an excitation wavelength near the S 1 (0–0) vibronic transition, this picosecond shift is assigned to solvation in methanol. ,,, The sensitivity of this chromophore to the relaxation of its solvent shells means that it probably could be used as a probe for environment relaxation in proteins. , We also performed experiments on NBz with 266 nm excitation to compare directly with the experiments on NBzOx and nicotinamide, where the first transitions correspond to a 266 nm-centered band. The respective traces for excitation at 266 nm are included in the Supporting Information for representative wavelengths (Figure S1).…”

Section: Resultsmentioning

confidence: 99%

“…Due to the general interest in the mechanisms for the electronic deactivation of biologically important molecules − and the relevance of these compounds in cellular sciences, we present here the first experimental and computational study of the intrinsic photophysics of the nicotinamide chromophore with a focus on the oxidized forms. For this, we explored three model systems: nicotinamide (niacinamide), 1-benzyl-1,4-dihydronicotinamide (NBz, a nicotinamide-only NADH model), and 1-benzyl-3-carbamoyl-pyridinium in the form of the bromide salt (NBzOx, a nicotinamide-only model for the oxidized form, NAD + ).…”

Section: Introductionmentioning

confidence: 99%

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Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms

Reza,

Durán-Hernández,

González-Cano

et al. 2023

J. Phys. Chem. B

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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 S 1 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 S 1 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 S 1 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* S 1 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* S 1 state.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms

Reza,

Durán-Hernández,

González-Cano

et al. 2023

J. Phys. Chem. B

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Sub-100-fs energy transfer in coenzyme NADH is a coherent process assisted by a charge-transfer state

Jaiswal,

Aranda Ruiz,

Petropoulos

et al. 2024

Nat Commun

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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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Ultrafast fluorescence dynamics of NADH in aprotic solvents: Quasi-static self-quenching unmasked

Cited by 2 publications

References 48 publications

Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms

Primary Photophysics of Nicotinamide Chromophores in Their Oxidized and Reduced Forms

Sub-100-fs energy transfer in coenzyme NADH is a coherent process assisted by a charge-transfer state

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