Anharmonic Backbone Vibrations in Ultrafast Processes at the DNA鈥揥ater Interface

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• 作者：Torsten Siebert ; Biswajit Guchhait ; Yingliang Liu ; Rene Costard ; Thomas Elsaesser
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：July 30, 2015
• 年：2015
• 卷：119
• 期：30
• 页码：9670-9677
• 全文大小：505K
• ISSN：1520-5207

文摘

The vibrational modes of the deoxyribose-phosphodiester backbone moiety of DNA and their interactions with the interfacial aqueous environment are addressed with two-dimensional (2D) infrared spectroscopy on a femto- to picosecond time scale. Beyond the current understanding in the harmonic approximation, the anharmonic character and delocalization of the backbone modes in the frequency range from 900 to 1300 cm^鈥? are determined with both diagonal anharmonicities and intermode couplings on the order of 10 cm^鈥?. Mediated by the intermode couplings, energy transfer between the backbone modes takes place on a picosecond time scale, parallel to vibrational relaxation and energy dissipation into the environment. Probing structural dynamics noninvasively via the time evolution of the 2D lineshapes, limited structural fluctuations are observed on a 300 fs time scale of low-frequency motions of the helix, counterions, and water shell. Structural disorder of the DNA鈥搘ater interface and DNA鈥搘ater hydrogen bonds are, however, preserved for times beyond 10 ps. The different interactions of limited strength ensure ultrafast vibrational relaxation and dissipation of excess energy in the backbone structure, processes that are important for the structural integrity of hydrated DNA.