Goddard N L, Bonnet G, Krichevsky O, Libchaber A
Center for Studies in Physics and Biology, The Rockefeller University, New York, New York 10021, USA.
Phys Rev Lett. 2000 Sep 11;85(11):2400-3. doi: 10.1103/PhysRevLett.85.2400.
Single stranded DNA (ssDNA) equilibrium dynamics are investigated using a fluorophore/quencher-labeled hairpin structure which thermally fluctuates between open and closed states. Temporal correlations of the fluorescence fluctuations are used to determine the energy barrier to conformational change. We find that ssDNA distortion is purely entropic for poly(T) but requires an additional enthalpy of +0.5 kcal x mol(-1) x base(-1) for poly(A), consistent with the disruption of base stacking. Such sequence dependent dynamics challenge the classical model of ssDNA as a completely flexible coil.
利用一种在开放和闭合状态之间热波动的荧光团/猝灭剂标记的发夹结构，研究了单链DNA（ssDNA）的平衡动力学。荧光涨落的时间相关性被用于确定构象变化的能垒。我们发现，对于聚（T），ssDNA的扭曲纯粹是熵驱动的，但对于聚（A），则需要额外的0.5千卡·摩尔⁻¹·碱基⁻¹的焓，这与碱基堆积的破坏一致。这种序列依赖性动力学挑战了将ssDNA视为完全柔性线圈的经典模型。
