Contributions of the Distance-Dependent Reorganization Energy and Proton-Transfer to the Hole-Transfer Process in DNA

✍ Scribed by Tadao Takada; Kiyohiko Kawai; Mamoru Fujitsuka; Tetsuro Majima

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 422 KB
• Volume: 11
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200500052

✦ Synopsis

Abstract

A kinetic study of the single‐step hole transfer in DNA was performed by measuring time‐resolved transient absorption. DNA molecules with various sequences were designed and conjugated with naphthalimide (NI) and phenothiazine (PTZ) to investigate the sequence and distance dependence of the single‐step hole transfer between guanines (Gs). Hole injection into DNA was accomplished by excitation of the NI site with a 355 nm laser pulse, and the kinetics of the hole‐transfer process were investigated by monitoring the transient absorption of the PTZ radical cation (PTZ^.^^+^). Kinetic analysis of the time profile of PTZ^.^^+^ based on the kinetic model showed that the distance dependence of the hole‐transfer process was significantly influenced by the DNA sequence. Results of temperature‐ and isotope‐effect experiments demonstrated that the activation energy increased as the number of bridge bases separating the Gs increased. This is because of the distance‐dependent reorganization energy and contribution of the proton‐transfer process to the hole transfer in DNA.