Fluorescence quenching over short range in a donor-DNA-acceptor system

Inhibiting guanine oxidation and enhancing the excess-electron-transfer efficiency of a pyrene-modified oligonucleotide by introducing an electron-donating group on pyrene

PipPyU and OMePyU enhance the reduction efficiency without oxidizing guanine in DNA-mediated electron transfer.

Preparation and characterization of pyrene modified uridine derivatives as potential electron donors in RNA

Charge transfer across double stranded DNA was observed for the first time about 20 years ago, and ever since it has been the subject of a large number of studies. RNA has been hardly investigated in this regard, which not least is due to the lack of suitably functionalized ribonucleotide building blocks to serve as electron sources upon incorporation into oligoribonucleotides. We have synthesized two uridine derivatives carrying pyrene or dimethylaminopyrene linked to C5 of the nucleobase. The key to successful synthesis was the adaptation of Suzuki-Miyaura conditions to the coupling of the pyrene moiety with the ribonucleoside. Final decoration of the pyrenylated nucleosides with standard 5'-O- and 2'-O-protecting groups and subsequent 3'-O-phosphitylation delivered the building blocks for incorporation into RNA. Spectroscopic analysis of the two pyrenylated uridines and of the accordingly modified oligonucleotides showed that in particular the dimethyaminopyrene functionalized nucleoside is a promising candidate as an electron source for RNA charge transport studies.

Distance dependence of hole transfer rates from G radical cations to GGG traps in DNA

Relative reaction rates for hole transfer between G radical cations and GGG triplets in DNA, through different bridges of varying lengths, are numerically calculated and the obtained results are compared with corresponding experimental observations [Giese et al., 2001, Nature, 412, 318; Angew. Chem., Int. Ed., 1999, 38, 996]. Hole donors and acceptors are separated either by (T-A)n bridges or by N repeated barriers consisting of (T-A,T-A) double base-pairs which are connected through single G-C base-pairs. In the former case, hole transfer rates show a strong exponential decrease with the length of the bridge for short bridges, while a switching to weak distance dependence has been observed for longer bridges. In the latter case, a power law seems to better describe the distance dependence of charge transfer rates. All these experimental observations are qualitatively reproduced by our simulations without any adjustable parameter, considering only tunneling as the charge transfer mechanism. Physical insights into the mechanism providing the switching behavior in the case of (T-A)n bridges are presented through an analysis of the eigenfunctions of the system.