Local dynamics coupled to hydration water determines DNA-sequence-dependent deformability

Nakagawa, Hiroshi   ; Yonetani, Yoshiteru; Nakajima, Kenji  ; Kawamura, Seiko   ; Kikuchi, Tatsuya  ; Inamura, Yasuhiro  ; Kataoka, Mikio; Kono, Hidetoshi

Molecular dynamics (MD) simulations and Quasi-Elastic Neutron Scattering (QENS) experiments were conducted on hydrated two DNA dodecamers with distinct deformability; 5'CGCGAATTCGCG3' and 5'CGCGTTAACGCG3'. The former is known to be rigid and the latter to be flexible. The mean-square displacements (MSDs) of DNA dodecamers exhibit so-called dynamical transition around 200-240 K for both sequences. To investigate the DNA sequence dependent dynamics, the dynamics of DNA and hydration water above the transition temperature were examined using both MD simulations and QENS experiments. The fluctuation amplitude of the AATT central tetramer is smaller, and its relaxation time is longer, than that observed in TTAA, suggesting that the AT step is kinetically more stable than TA. The sequence-dependent local base pair step dynamics correlate with the kinetics of breaking the hydrogen bond between DNA and hydration water. The sequence dependent DNA base pair step fluctuations appear above the dynamical transition temperature. Together with these results, we conclude that DNA deformability is related to the local dynamics of base pair step, themselves coupled to hydration water in the minor groove.