Density functional calculations with B3LYP/aug-cc-pVDZ level of theory suggest that the vertical ionization energy (VIE) is minimum for 0° orientation angle of guanine-cytosine (GC). n (. n=. 2-6) base pairs, and maximum at around 30°, which is close to the natural base orientation angle (36°) in DNA. As the (GC). n cluster size is increased, the VIE value is decreased substantially from n=. 1 to n=. 3 (7.23-5.76. eV) followed by a less dramatic decrease for larger n values. In each cationic (GC). n cluster, the charge distribution among the G bases shows a pattern that depends upon odd or even number of base pairs in the cluster. At a very low temperature, when the orientation angle is frozen to its equilibrium value (around 36°), the CT rate is expected to drop significantly (large VIE value) in comparison with the rates at higher temperatures when small orientation angles are accessible with lower VIE values.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Physical and Theoretical Chemistry