scholarly journals Theoretical Study on the Photo-Oxidation and Photoreduction of an Azetidine Derivative as a Model of DNA Repair

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2911
Author(s):  
Miriam Navarrete-Miguel ◽  
Antonio Francés-Monerris ◽  
Miguel A. Miranda ◽  
Virginie Lhiaubet-Vallet ◽  
Daniel Roca-Sanjuán
Keyword(s):  
Electron Transfer ◽  
Energy Barrier ◽  
Ring Opening ◽  
Dna Lesions ◽  
Barrier Heights ◽  
Dna Lesion ◽  
Electron Reduction ◽  
The Stability ◽  
Electron Transfer Processes

Photocycloreversion plays a central role in the study of the repair of DNA lesions, reverting them into the original pyrimidine nucleobases. Particularly, among the proposed mechanisms for the repair of DNA (6-4) photoproducts by photolyases, it has been suggested that it takes place through an intermediate characterized by a four-membered heterocyclic oxetane or azetidine ring, whose opening requires the reduction of the fused nucleobases. The specific role of this electron transfer step and its impact on the ring opening energetics remain to be understood. These processes are studied herein by means of quantum-chemical calculations on the two azetidine stereoisomers obtained from photocycloaddition between 6-azauracil and cyclohexene. First, we analyze the efficiency of the electron-transfer processes by computing the redox properties of the azetidine isomers as well as those of a series of aromatic photosensitizers acting as photoreductants and photo-oxidants. We find certain stereodifferentiation favoring oxidation of the cis-isomer, in agreement with previous experimental data. Second, we determine the reaction profiles of the ring-opening mechanism of the cationic, neutral, and anionic systems and assess their feasibility based on their energy barrier heights and the stability of the reactants and products. Results show that oxidation largely decreases the ring-opening energy barrier for both stereoisomers, even though the process is forecast as too slow to be competitive. Conversely, one-electron reduction dramatically facilitates the ring opening of the azetidine heterocycle. Considering the overall quantum-chemistry findings, N,N-dimethylaniline is proposed as an efficient photosensitizer to trigger the photoinduced cycloreversion of the DNA lesion model.

scholarly journals Reflections on the outer-sphere mechanism of electron transfer

1996 ◽  
Vol 74 (5) ◽  
pp. 631-638 ◽  
Author(s):  
Thomas W. Swaddle
Keyword(s):  
Electron Transfer ◽  
Large Change ◽  
Outer Sphere ◽  
Pressure Effects ◽  
Spherical Approximation ◽  
Mean Spherical Approximation ◽  
Redox Kinetics ◽  
Electron Transfer Processes ◽  
Low Pressures

The quantitative efficacy of the Stranks–Marcus–Hush theory of volumes of activation ΔV‡ for outer-sphere electron transfer between metal complexes in solution is assessed. The theory predicts ΔV‡ accurately for several couples in aqueous solution, but is satisfactory for polar nonaqueous solvents only at pressures of ca. 100 MPa and above, and accuracy is not improved when the molecular nature of the solvent is allowed for through the Mean Spherical Approximation approach. At low pressures, the calculations become numerically unstable when the isothermal compressibility of the solvent is high and its relative permittivity is low, particularly for the more highly charged couples. For aqueous systems, departures from the predicted ΔV‡ afford insights into the role of the counterions, the incursion of inner-sphere pathways, the enhanced reactivity of CoIII/II cage complexes relative to conventional chelates, and the question of "spin forbiddenness" of electron transfer processes that involve a large change in spin multiplicity. Key words: redox kinetics, inorganic reaction mechanisms, pressure effects, Marcus–Hush theory, activation volumes.

On the theory of electron-transfer processes in aqueous solutions

1954 ◽  
Vol 222 (1148) ◽  
pp. 128-141 ◽  
Keyword(s):  
Electron Transfer ◽  
Point Of View ◽  
Complex Ions ◽  
Gaseous State ◽  
Biochemical Processes ◽  
Transfer Processes ◽  
Oxidation Reduction ◽  
Mechanical Interpretation ◽  
Electron Transfer Processes

It has been realized for some time that simple electron-transfer processes play an important part in the mechanism of many oxidation-reduction reactions in solution. An attempt has been made to give a quantum-mechanical interpretation of these processes on the basis of the earlier theories of electron transfer in the gaseous state (Landau 1932; Bates & Massey 1943). The present treatment for solutions takes into account the role of the solvent, with particular reference to the operation of the Franck—Condon principle and it also leads to some definite picture of the transition state for the electron transfer process. A number of examples are discussed, including electron transfer between like ions of different valency and also reactions involving complex ions, e.g. metal porphyrins, the reactions of which are of importance in certain biochemical processes. It appears that the application of certain theoretical principles leads to a satisfactory understanding of electron-transfer processes in solution from a qualitative and, in some cases, also from a semi-quantitative point of view.

Cyclic voltammetry of diphenylpicrylhydrazyl in tetrahydrofuran

1968 ◽  
Vol 46 (8) ◽  
pp. 1337-1340 ◽  
Author(s):  
B. Lionel Funt ◽  
Derek G. Gray
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Free Radical ◽  
Anionic Polymerization ◽  
Single Electron ◽  
Single Electron Transfer ◽  
Transfer Processes ◽  
Suitable Medium ◽  
The Stability ◽  
Electron Transfer Processes

Cyclic voltammetry has revealed four reversible single electron transfer processes in the oxidation and reduction of diphenylpicrylhydrazyl (DPPH) in tetrahydrofuran (THF). These are associated with a cation, a free radical, a monoanion, a dianion radical, and a trianion of DPPH.THF is a good solvent for cyclic voltammetry as evidenced by the stability of the products generated at the electrodes. It is also one of the few excellent solvents for anionic polymerization and is therefore a remarkably suitable medium for studies of electropolymerization phenomena.

Unusual Role of Oxygen in Electron-Transfer Processes

2002 ◽  
Vol 124 (16) ◽  
pp. 4212-4213 ◽  
Author(s):  
Sergei Smirnov ◽  
Ivan Vlassiouk ◽  
Olaf Kutzki ◽  
Michael Wedel ◽  
Franz-Peter Montforts
Keyword(s):  
Electron Transfer ◽  
Transfer Processes ◽  
Electron Transfer Processes

scholarly journals Forever Young: Structural Stability of Telomeric Guanine-Quadruplexes in Presence of Oxidative DNA Lesions

2020 ◽  
Author(s):  
Tom Miclot ◽  
Camille Corbier ◽  
Alessio Terenzi ◽  
Cécilia Hognon ◽  
Stéphanie Grandemange ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Molecular Dynamics ◽  
Structural Stability ◽  
Md Simulations ◽  
Dna Lesions ◽  
Computational Investigation ◽  
Telomeric Dna ◽  
G Quadruplex ◽  
The Stability

AbstractHuman telomeric DNA (h-Telo), in G-quadruplex (G4) conformation, is characterized by a remarkable structural stability that confers it the capacity to resist to oxidative stress producing one or even clustered 8-oxoguanine lesions. We present a combined experimental/computational investigation, by using circular dichroism in aqueous solutions, cellular immunofluorescence assays and molecular dynamics (MD) simulations, that identifies the crucial role of the stability of G4s to oxidative lesions, related also to their biological role as inhibitors of telomerase, an enzyme overexpressed in most cancers associated to oxidative stress.

The electron that breaks the catalyst’s back – excited state dynamics in intermediates of molecular photocatalysts

2021 ◽  
Author(s):  
Carolin Müller ◽  
Ilse Friedländer ◽  
Benedikt Bagemihl ◽  
Sven Rau ◽  
Benjamin Dietzek
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Single Electron ◽  
Intramolecular Electron Transfer ◽  
Excited State Dynamics ◽  
Transfer Processes ◽  
Electron Reduction ◽  
Electron Transfer Processes ◽  
Franck Condon

In situ spectroelectrochemical studies focussing on the Franck-Condon region and sub-ns electron transfer processes in Ru(II)-tpphz-Pt(II) based photocatalysts reveal that single-electron reduction effectively hinders intramolecular electron transfer between the photoexcited...

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