RNA-Mediated Electron Transfer: Double Exponential Distance Dependence

Abstract

We describe the long-range excess electron transfer through RNA duplexes consisting of a pyrene electron donor and a nitrobenzene electron acceptor that shows double exponential distance dependence.

Investigation of Excess‐Electron Transfer in DNA Double‐Duplex Systems Allows Estimation of Absolute Excess‐Electron Transfer and CPD Cleavage Rates

“…Based on these relative values, we can assume that the reduction of the CPD lesion, and not the cyclobutane opening, is the rate-determining step in the electrontrapping process within our DNA double duplexes. Furthermore, we were able to estimate maximum rate constants for excess-electron transfer along a pure (A:T) 4 sequence and mixed (N:N) 4 sequences. We believe our new double-duplex system gives valuable insights into the kinetics of excesselectron transfer, especially new information about the rate of electron trapping by a T=T dimer and by BrdA and BrdG.…”

“…[8,25] In addition, our previous results for excess-electron transfer along mixed sequences such as TTCT or TTCC showed that transfer along these sequences is nearly as fast as electron detection by BrdA and BrdG, because the sequence dependence was hardly resolved. [20] From our experiment through (AT) 4 sequences, we can estimate that the reduction and debromination of BrdA and BrdG proceeds with maximum overall rates of 3.9 10 7 (BrdA) and 2.1 10 7 s À1 (BrdG). These rates roughly correspond to the excess-electron transfer rates through mixed TTCT and TTCC sequences.…”

“…[3] Over the past few years, electron injection into a DNA duplex and movement of an injected excess electron through a DNA duplex have been intensively investigated theoretically and with various DNAbased model compounds. [4][5][6][7][8][9][10] It is now clear that an injected (excess) electron can hop through the DNA duplex by using pyrimidine bases as stepping stones. This allows cleavage of CPD lesions located even a few base pairs away from the injection site of the excess electron.…”

“…This idea is supported by the result, from Giese, Carell and co-workers, that an electron can "overhop" a CPD lesion without opening it. [29] This now allows us to estimate that the rate of electron transfer along an (A:T) 4 sequence is, in the best case, slower than 1.4 10 8 s À1 (BrdU cleavage) and faster than 1.8 10 7 s À1 (T=T dimer cleavage in the duplex). This result is in full agreement with recent results by Lewis and co-workers and by Majima and co-workers, who estimated a rate of about 10 7 and 10 8 s…”

Nucleotides and nucleic acids; oligo- and polynucleotides

“…183 A 2'-O-modified nitrobenzene uridine derivative has been used as an electron acceptor. 545 Various nucleoside analogues have been used as electron donors or acceptors, for example 2-aminopurine 547 and the novel pyrimidine analogue (90), 548 and 5-bromo-dU as electron acceptor. 546,549 Charge transport has been investigated across T:T mispairs, 550 in a G-quadruplex, 551 and in an adenosine aptamer.…”