Dynamics and efficiency of photoinduced charge transport in DNA: Toward the elusive molecular wire

2013 ◽  
Vol 85 (7) ◽  
pp. 1379-1387 ◽  
Author(s):  
Frederick D. Lewis ◽  
Michael R. Wasielewski

Experimental investigations of photoinduced charge transport in synthetic DNA capped hairpins possessing electron acceptor and donor stilbene chromophores at either end have established the mechanism, dynamics, and efficiency of charge transport in DNA. The mechanism for charge transport in repeating A-T base pairs (A-tracts) was found to change from single-step superexchange at short distances to multistep incoherent hole hopping at longer distances. The rate constants for base-to-base hole hopping in longer A- and G-tract sequences are 1.2 × 109 s–1 and 4.3 × 109 s–1, respectively, considerably slower than the rate constants associated with molecular wires. Even slower rate constants are observed for alternating or random base sequences such as those encountered in natural DNA. The efficiency of charge separation in capped hairpins with A-tract sequences is also low as a consequence of the competition of hole hopping with charge recombination. Significantly higher efficiencies for charge separation are possible using diblock purine base sequences consisting of two or three adenines followed by a larger number of guanines. The short A-block serves as a molecular rectifier, slowing down charge recombination. More efficient charge separation can also be achieved using non-natural bases or by using the triplet acceptor anthraquinone for hole injection.

2015 ◽  
Vol 185 ◽  
pp. 105-120 ◽  
Author(s):  
Arunoday P. N. Singh ◽  
Michelle A. Harris ◽  
Ryan M. Young ◽  
Stephen A. Miller ◽  
Michael R. Wasielewski ◽  
...  

The effects of an artificial cyclohexyl base pair on the quantum yields of fluorescence and dynamics of charge separation and charge recombination have been investigated for several synthetic DNA hairpins. The hairpins possess stilbenedicarboxamide, perylenediimide, or naphthalenediimide linkers and base-paired stems. In the absence of the artificial base pair hole injection into both adenine and guanine purine bases is exergonic and irreversible, except in the case of stilbene with adenine for which it is slightly endergonic and reversible. Insertion of the artificial base pair renders hole injection endergonic or isoergonic except in the case of the powerful naphthalene acceptor for which it remains exergonic. Both hole injection and charge recombination are slower for the naphthalene acceptor in the presence of the artificial base pair than in its absence. The effect of an artificial base pair on charge separation and charge recombination in hairpins possessing stilbene and naphthalene acceptor linkers and a stilbenediether donor capping group has also been investigated. In the case of the stilbene acceptor–stilbene donor capped hairpins photoinduced charge separation across six base pairs is efficient in the absence of the artificial base pair but does not occur in its presence. In the case of the naphthalene acceptor–stilbene donor capped hairpins the artificial base pair slows but does not stop charge separation and charge recombination, leading to the formation of long-lived charge separated states.


2014 ◽  
Vol 16 (47) ◽  
pp. 25775-25788 ◽  
Author(s):  
Igor V. Sazanovich ◽  
Jonathan Best ◽  
Paul A. Scattergood ◽  
Michael Towrie ◽  
Sergei A. Tikhomirov ◽  
...  

The Pt(ii)-based molecular triad engages in step-wise photoinduced charge-separation; the charge recombination occurs through-space via two distinct pathways.


2019 ◽  
Vol 21 (8) ◽  
pp. 4387-4393 ◽  
Author(s):  
Lorenzo Cupellini ◽  
Paweł Wityk ◽  
Benedetta Mennucci ◽  
Janusz Rak

Neither the rates of photoinduced charge separation nor charge recombination account for the substantial damage observed in the 5′-ABrU sequence.


2014 ◽  
Vol 136 (37) ◽  
pp. 12966-12973 ◽  
Author(s):  
Duoduo Bao ◽  
Srigokul Upadhyayula ◽  
Jillian M. Larsen ◽  
Bing Xia ◽  
Boriana Georgieva ◽  
...  

2006 ◽  
Vol 79 (12) ◽  
pp. 1860-1868 ◽  
Author(s):  
Mamoru Fujitsuka ◽  
Takashi Makinoshima ◽  
Atushi Takamizawa ◽  
Yasuyuki Araki ◽  
Osamu Ito ◽  
...  

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