Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
J Phys Chem B. 2009 Dec 17;113(50):16276-84. doi: 10.1021/jp907323d.
The structure, spectroscopy, and photophysical behavior of a series of hairpin-forming conjugates possessing a 5'-tethered N-alkylpyrenecarboxamide chromophore have been investigated. Comparison of the NMR spectra of the conjugates and analogs lacking the tethered pyrene indicates that the pyrene does not behave as an end-capping group but rather is intercalated between the two terminal hairpin base pairs. An intercalated structure is also consistent with the thermodynamic parameters for hairpin formation and the steady state and transient spectral properties of the conjugates. Quenching of the pyrene fluorescence and transient absorption spectra is observed only when guanine is located in one of the two terminal base pairs and is attributed to hole injection from singlet pyrene to guanine. The fast component of the transient decay is more rapid when guanine is located in the second vs first base pair, consistent with an intercalated but not an end-capped geometry. Spectral broadening of ultraviolet, fluorescence, and transient absorption spectra is attributed to multiple ground state conformations.
已经研究了一系列具有 5'-键合 N-烷基吡啶酰胺发色团的发夹形成缀合物的结构、光谱和光物理行为。缀合物和缺乏键合芘的类似物的 NMR 光谱的比较表明，芘不作为端封基团，而是被嵌入两个末端发夹碱基对之间。嵌入结构也与发夹形成的热力学参数以及缀合物的稳态和瞬态光谱性质一致。只有当鸟嘌呤位于两个末端碱基对之一中时，才会观察到芘荧光的猝灭和瞬态吸收光谱，这归因于从单重态芘到鸟嘌呤的空穴注入。当鸟嘌呤位于第二个碱基对而不是第一个碱基对中时，瞬态衰减的快组分更快，与嵌入而不是端封的几何形状一致。紫外、荧光和瞬态吸收光谱的光谱展宽归因于多个基态构象。
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