scholarly journals Excited states of protonated DNA/RNA bases

2014 ◽  
Vol 16 (22) ◽  
pp. 10643-10650 ◽  
Author(s):  
Matias Berdakin ◽  
Géraldine Féraud ◽  
Claude Dedonder-Lardeux ◽  
Christophe Jouvet ◽  
Gustavo A. Pino
Keyword(s):  
Excited State ◽  
Excited States ◽  
Tautomeric Form ◽  
Excited State Lifetime ◽  
Rna Bases

The excited state lifetime of protonated DNA/RNA bases is strongly dependent on the tautomeric form.

Fluorescence Enhancement of a Microbial Rhodopsin via Electronic Reprogramming

2018 ◽  
Author(s):  
Maria del Carmen Marin ◽  
Damianos Agathangelou ◽  
Yoelvis Orozco-González ◽  
Alessio Valentini ◽  
Yoshitaka Kato ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Excited States ◽  
Fluorescence Quantum Yield ◽  
Fluorescence Enhancement ◽  
Energy Surface ◽  
Wild Type ◽  
Excited State Lifetime ◽  
State Potential ◽  
Microbial Rhodopsin

The manuscript reports on two mutations of the photo-sensory protein Anabaena Sensory Rhodopsin and how these mutations modify the fluorescence quantum yield with respect to the wild-type protein. Experimental results are presented and explained theoretically on the basis of mixing of the S1 and S2 excited states. This mixing modulated by electrostatic and steric effects, tunes the excited state potential energy surface, and thereby the excited state lifetime and the fluorescence quantum yield.<br>

scholarly journals Sequestration Effect on the Open-Cyclic Switchable Property of Warfarin by Cyclodextrin: Ultrafast Dynamical Study

2017 ◽  
Author(s):  
Naji Al-Dubaili ◽  
Na'il Saleh
Keyword(s):  
Excited State ◽  
Excited States ◽  
Time Resolved Fluorescence ◽  
Excited State Lifetime ◽  
Deprotonated Form ◽  
Dynamical Study ◽  
Visible Absorption ◽  
Time Resolved ◽  
Pka Values ◽  
Fluorescence Measurements

The excited-state lifetimes of the anticoagulant drug warfarin (W) in water and in the absence and presence of methyl-&beta;-cyclodextrins (Me-&beta;-CD) were recorded using time-resolved fluorescence measurements. Selective excitation of the open and cyclic protonated isomers of W were acquired with laser emitting diodes (LED) producing 320 and 280 nm excitation pulses, respectively. Formation of the inclusion complex was checked by UV&ndash;visible absorption spectroscopy, and the values of binding constants (2.9 &times; 103 M&ndash;1 and 4.2 &times; 102 M&ndash;1 for protonated and deprotonated forms, respectively) were extracted from the spectrophotometric data. Both absorption and time-resolved fluorescence results established that the interior of the macromolecular host binds preferentially the open protonated form, red shifts the maximum of its absorption of light at ~305 nm, extends its excited-state lifetime, and decreases its emission quantum yield (ФF). Collectively, sequestration of the open guest molecules decreases markedly their radiative rate constants (kr), likely due to formation of hydrogen-bonded complexes in both the ground and excited states. Due to lack of interactions, no change was observed in the excited-state lifetime of the cyclic form in the presence of Me-&beta;-CD. The host also increases the excited-state lifetime and ФF of the drug deprotonated form (W&macr;). These later findings could be attributed to the increased rigidity inside the cavity of Me-&beta;-CD. The pKa values extracted from the variations of the UV&ndash;visible absorption spectra of W versus the pH of aqueous solution showed that the open isomer is more acidic in both ground and excited states. The positive shifts in pKa values induced by three derivatives of cyclodextrins: HE-&beta;-CD, Ac-&beta;-CD, and Me-&beta;-CD supported the preferential binding of these hosts to open isomers over cyclic.

Fluorescence Enhancement of a Microbial Rhodopsin via Electronic Reprogramming

2018 ◽  
Author(s):  
Damianos Agathangelou ◽  
Yoelvis Orozco-González ◽  
Alessio Valentini ◽  
Yoshitaka Kato ◽  
Rei Abe-Yoshizumi ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Excited States ◽  
Fluorescence Quantum Yield ◽  
Fluorescence Enhancement ◽  
Energy Surface ◽  
Wild Type ◽  
Excited State Lifetime ◽  
State Potential ◽  
Microbial Rhodopsin

The manuscript reports on two mutations of the photo-sensory protein Anabaena Sensory Rhodopsin and how these mutations modify the fluorescence quantum yield with respect to the wild-type protein. Experimental results are presented and explained theoretically on the basis of mixing of the S1 and S2 excited states. This mixing modulated by electrostatic and steric effects, tunes the excited state potential energy surface, and thereby the excited state lifetime and the fluorescence quantum yield.<br>

Fluorescence Enhancement of a Microbial Rhodopsin via Electronic Reprogramming

2018 ◽  
Author(s):  
Maria del Carmen Marin ◽  
Damianos Agathangelou ◽  
Yoelvis Orozco-González ◽  
Alessio Valentini ◽  
Yoshitaka Kato ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Excited States ◽  
Fluorescence Quantum Yield ◽  
Fluorescence Enhancement ◽  
Energy Surface ◽  
Wild Type ◽  
Excited State Lifetime ◽  
State Potential ◽  
Microbial Rhodopsin

The manuscript reports on two mutations of the photo-sensory protein Anabaena Sensory Rhodopsin and how these mutations modify the fluorescence quantum yield with respect to the wild-type protein. Experimental results are presented and explained theoretically on the basis of mixing of the S1 and S2 excited states. This mixing modulated by electrostatic and steric effects, tunes the excited state potential energy surface, and thereby the excited state lifetime and the fluorescence quantum yield.<br>

The photochemical reaction of tris(ethylenediamine)cobalt(III) ion with ferrocyanide

1981 ◽  
Vol 59 (4) ◽  
pp. 647-651 ◽  
Author(s):  
Cooper H. Langford ◽  
Roger L. P. Sasseville
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Photochemical Reaction ◽  
Ion Pairs ◽  
Ligand Field ◽  
Excited State Lifetime ◽  
Photochemical Formation ◽  
Reaction Proceeds ◽  
Reactive Excited State

The photochemical formation of [Cl(en)2Co—N≡C—Fe(CN)5]2− from Co(en)33+ and Fe(CN)64− is explored. Earlier evidence established that the reaction proceeds via electron transfer. Ligand field Co(III) excited states are clearly indicated to be effective. There is evidence that free Fe(CN)64− can scavenge these excited states or their successors arising in ion pairs with Fe(CN)64−. This suggests that the reactive excited state lifetime is at least comparable to the rate of diffusional encounters. However, racemization does not accompany reaction if (+)589Co(en)33+ is the reactant. Wavelength studies indicate approximate wavelength independence as far as 647.1 nm. These results are in contrast with the behaviour of photosubstitution yields for Co(III) amines.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

The Malleable Excited States of Benzothiadiazole Dyes and Investigation of their Potential for Photochemical Control

2019 ◽  
Author(s):  
Caroline C. Warner ◽  
andrea thooft ◽  
Bryan J. Lampkin ◽  
selin demirci ◽  
Brett VanVeller
Keyword(s):  
Excited State ◽  
Excited States ◽  
Polar Solvent ◽  
Nonpolar Solvent ◽  
Photochemical Degradation ◽  
Solvent Lead ◽  
Environmentally Sensitive

<p>A strategy to control the efficiency of a photocleavage reaction based on changing the nature of the excited state is presented. A novel class of photoactive compounds has been synthesized by combining the classical o-nitrobenzyl scaffold with an environmentally sensitive dye, 4-amino-nitrobenzothiazole. Irradiation in a polar solvent lead to an excited state that is inoperative for photochemistry whereas excitation in a nonpolar solvent lead to an excited state that is photochemically active. A photochemical degradation appears to be the preferred process in contrast to the intended photocleavage process.</p>

Excited State Tracking During the Relaxation of Coordination Compounds

2018 ◽  
Author(s):  
Juan Sanz García ◽  
Martial Boggio-Pasqua ◽  
Ilaria Ciofini ◽  
Marco Campetella
Keyword(s):  
Excited State ◽  
Excited States ◽  
Potential Energy Surfaces ◽  
Photochemical Reactions ◽  
Complex Nature ◽  
Electronic Excited States ◽  
Ruthenium Nitrosyl ◽  
State Tracking ◽  
Energy Surfaces ◽  
Electronic Wavefunction

<div>The ability to locate minima on electronic excited states (ESs) potential energy surfaces (PESs) both in the case of bright and dark states is crucial for a full understanding of photochemical reactions. This task has become a standard practice for small- to medium-sized organic chromophores thanks to the constant developments in the field of computational photochemistry. However, this remains a very challenging effort when it comes to the optimization of ESs of transition metal complexes (TMCs), not only due to the presence of several electronic excited states close in energy, but also due to the complex nature of the excited states involved. In this article, we present a simple yet powerful method to follow an excited state of interest during a structural optimization in the case of TMC, based on the use of a compact hole-particle representation of the electronic transition, namely the natural transition orbitals (NTOs). State tracking using NTOs is unambiguously accomplished by computing the mono-electronic wavefunction overlap between consecutive steps of the optimization. Here, we demonstrate that this simple but robust procedure works not only in the case of the cytosine but also in the case of the ES optimization of a ruthenium-nitrosyl complex which is very problematic with standard approaches.</div>

scholarly journals Impact of the Dynamic Electron Correlation on the Unusually Long Excited-State Lifetime of Thymine

2021 ◽  
pp. 4339-4346
Author(s):  
Woojin Park ◽  
Seunghoon Lee ◽  
Miquel Huix-Rotllant ◽  
Michael Filatov ◽  
Cheol Ho Choi
Keyword(s):  
Excited State ◽  
Electron Correlation ◽  
Excited State Lifetime

Measurement of excited-state lifetime using two-pulse photon echoes in rubidium vapor

2007 ◽  
Vol 24 (3) ◽  
pp. 671 ◽  
Author(s):  
E. A. Rotberg ◽  
B. Barrett ◽  
S. Beattie ◽  
S. Chudasama ◽  
M. Weel ◽  
...  
Keyword(s):  
Excited State ◽  
Excited State Lifetime ◽  
Rubidium Vapor ◽  
Photon Echoes ◽  
Pulse Photon
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