Ultrafast Site-Specific Fluorescence Quenching of 2-Aminopurine in a DNA Hairpin Studied by Femtosecond Down-Conversion

作者：Gelot Thomas; Touron Touceda Patricia; Cregut Olivier; Leonard Jeremie; Haacke Stefan^*

来源：Journal of Physical Chemistry A, 2012, 116(11): 2819-2825.

DOI：10.1021/jp212187m

The Delta P(-)PBS analog of the DNA primary binding sequence (PBS) of the HIV-1 genome labeled at different positions by 2-aminopurine (2-AP) is investigated by a novel femtosecond fluorescence down-conversion experiment with 0.3-ps time resolution. The high signal-to-noise ratio of the fluorescence kinetics makes it possible to reveal four distinct decay times ranging from 0.8 ps to 2-3 ns for all the three labeling positions. This suggests the existence of at least four different quenching conformations of 2-AP with its nearest neighbors, and underscores the structural heterogeneity of the loop region of Delta P(-)PBS. Sub-5-ps components are found and attributed to stacking interactions of 2-AP with the flanking guanine (G) side chains, consistent with the NMR structure of Delta P(-)PBS. The observation of a significant increase of their total amplitude when 2-AP is positioned close to the rigid 3%26apos;-half of the G-rich stem gives further support to this assignment. Only a minor portion of conformations involves slow nanosecond collisional quenching.

• 出版日期2012-3-22