Effect of Backbone Flexibility on Charge Transfer Rates in Peptide Nucleic Acid Duplexes

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• 作者：Emil Wierzbinski ; Arnie de Leon ; Xing Yin ; Alexander Balaeff ; Kathryn L. Davis ; Srinivas Reppireddy ; Ravindra Venkatramani ; Shahar Keinan ; Danith H. Ly ; Marcela Madrid ; David N. Beratan ; Catalina Achim ; David H. Waldeck
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：June 6, 2012
• 年：2012
• 卷：134
• 期：22
• 页码：9335-9342
• 全文大小：393K
• 年卷期：v.134,no.22(June 6, 2012)
• ISSN：1520-5126

文摘

Charge transfer (CT) properties are compared between peptide nucleic acid structures with an aminoethylglycine backbone (aeg-PNA) and those with a 纬-methylated backbone (纬-PNA). The common aeg-PNA is an achiral molecule with a flexible structure, whereas 纬-PNA is a chiral molecule with a significantly more rigid structure than aeg-PNA. Electrochemical measurements show that the CT rate constant through an aeg-PNA bridging unit is twice the CT rate constant through a 纬-PNA bridging unit. Theoretical calculations of PNA electronic properties, which are based on a molecular dynamics structural ensemble, reveal that the difference in the CT rate constant results from the difference in the extent of backbone fluctuations of aeg- and 纬-PNA. In particular, fluctuations of the backbone affect the local electric field that broadens the energy levels of the PNA nucleobases. The greater flexibility of the aeg-PNA gives rise to more broadening, and a more frequent appearance of high-CT rate conformations than in 纬-PNA.