Photoinduced charge-transfer fluorescence quenching of a fluorescent dye produces the nonemissive charge-separated state, and subsequent charge recombination makes the reaction reversible. While the information available from the photoinduced charge-transfer process provides the basis for monitoring the microenvironment around the fluorescent dyes and such monitoring is particularly important in live-cell imaging and DNA diagnosis, the information obtainable from the charge recombination process is usually overlooked. When looking at fluorescence emitted from each single fluorescent dye, photoinduced charge-transfer, charge-migration, and charge recombination cause a "blinking" of the fluorescence, in which the charge-recombination rate or the lifetime of the charge-separated state (τ) is supposed to be reflected in the duration of the off time during the single-molecule-level fluorescence measurement. Herein, based on our recently developed method for the direct observation of charge migration in DNA, we utilized DNA as a platform for spectroscopic investigations of charge-recombination dynamics for several fluorescent dyes: TAMRA, ATTO 655, and Alexa 532, which are used in single-molecule fluorescence measurements. Charge recombination dynamics were observed by transient absorption measurements, demonstrating that these fluorescent dyes can be used to monitor the charge-separation and charge-recombination events. Fluorescence correlation spectroscopy (FCS) of ATTO 655 modified DNA allowed the successful measurement of the charge-recombination dynamics in DNA at the single-molecule level. Utilizing the injected charge just like a pulse of sound, such as a "ping" in active sonar systems, information about the DNA sequence surrounding the fluorescent dye was read out by measuring the time it takes for the charge to return.
Charge-separation and charge-recombination dynamics and oxidative DNA degradation were investigated for DNA modified with a photosensitizer (Sens) naphthalimide (NI), naphthaldiimide (ND), or anthraquinone (AQ). In all three Sens-modified DNA systems, the formation of long-lived charge-separated states was observed in which the lifetime increased with increasing numbers of A-T base pairs between Sens and the neighboring G-C base pair. The lifetime of the charge-separated state correlated well with the DNA damage yield, indicating that the charge-separated state provides time for the irreversible DNA oxidative damage to occur. The quantum yield of DNA damage was the lowest for ND-modified DNA due to the slow reaction of ND radical anion with molecular oxygen; the process needed to preclude charge recombination. The AQ-modified DNA resulted in the highest charge separation and subsequent DNA damage yield, which would be partly explained by the formation of the spin-forbidden triplet radical ion pairs during charge separation.
The kinetics and efficiency of oxidative degradation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in DNA during the photosensitized one-electron oxidation of DNA was investigated. The presence of 8-oxodGuo was shown to increase the lifetime of the charge-separated state in DNA by serving as a "hole sink" resulting in efficient and exclusive degradation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.