Onidas Delphine, Gustavsson Thomas, Lazzarotto Elodie, Markovitsi Dimitra
Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM-CNRS URA 2453, CEA/Saclay, 91191, Gif-sur-Yvette, France.
Phys Chem Chem Phys. 2007 Oct 7;9(37):5143-8. doi: 10.1039/b707882j. Epub 2007 Jul 31.
Polymeric and oligomeric DNA helices, poly(dAdT).poly(dAdT) and (dAdT)(10).(dAdT)(10), composed of 200-400 and 20 adenine-thymine base pairs, respectively, are studied by fluorescence upconversion. Fluorescence decays, anisotropy decays and time-resolved spectra, obtained for this alternating base sequence, are compared with those determined previously for the homopolymeric sequence (dA)(n).(dT)(n). It is shown that identical fluorescence decays may correspond to quite different anisotropy decays and vice versa, both varying with the emission wavelength, the base sequence and the duplex size. Our observations cannot be explained in terms of monomer and excimer emission exclusively, as concluded in the past on the basis of steady-state measurements. Excitons also contribute to the fluorescence. These are rapidly trapped by excimers, characterized by long-lived weak emission.
通过荧光上转换研究了分别由200 - 400个和20个腺嘌呤 - 胸腺嘧啶碱基对组成的聚合和寡聚DNA螺旋，聚（dAdT）·聚（dAdT）和（dAdT）₁₀·（dAdT）₁₀。将这种交替碱基序列获得的荧光衰减、各向异性衰减和时间分辨光谱与先前测定的同聚序列（dA）ₙ·（dT）ₙ的光谱进行比较。结果表明，相同的荧光衰减可能对应于相当不同的各向异性衰减，反之亦然，两者均随发射波长、碱基序列和双链体大小而变化。我们的观察结果不能仅用单体和准分子发射来解释，正如过去基于稳态测量得出的结论那样。激子也对荧光有贡献。这些激子会迅速被准分子捕获，其特征是具有长寿命的弱发射。
