Vectorial Photo-Energy Transmission on Chromophore-Array Constructed by DNA Assembly

在非共价分子组装体系中，用生色团/寡聚DNA偶联物构建了由约等于DNA双链体的一个节距（34 π）的调节距离分开的三种生色团的特定顺序排列。三种不同的发色团，6-羧基-4，5 '-二氯-2，7'-二甲氧基荧光素（JOE），6-羧基-四甲基罗丹明（塔姆拉）和6-羧基-X-罗丹明（ROX），分别作为能量供体，介体和受体，基于它们的重叠的激发和发射光谱。这些发色团连接在不同序列的10聚体寡聚DNA的5 ′端。将缀合物与由缀合物的互补序列组成的基质寡聚DNA（30聚体）混合，以在DNA双链体中构建连续的JOE-TAMRA-ROX阵列（发色团阵列），其中10个残基分隔每个发色团组分。利用飞秒脉冲激光系统，通过时间分辨荧光光谱和寿命测量，观察和分析了有序发色团阵列中荧光共振能量转移（FRET）引起的光能沿着DNA螺旋轴的矢量传输.结果表明，FRET发生在皮秒尺度上的供体发色团和受体发色团之间，通过介体发色团，通过多步FRET分子组装体（两个螺距，68 μ m）。此外，通过在DNA双链体（20 mer）的特定位置引入供体发色团（荧光素，Flu）和在DNA双链体末端引入受体发色团（六氯荧光素，Hex），研究了发色团之间的FRET距离依赖性。此外，通过在DNA双链体的某个位置引入2-5个供体发色团（Flu）和在DNA双链体末端引入受体发色团（Hex），研究了能量迁移引起的光捕获效应。观察到光捕获效应。

Specific sequential arrangements of three kinds of chromophores separated by regulated distances equaling approximately one pitch of the DNA duplex (34 Å) in non-covalent molecular assembly systems are constructed using chromophore/oligo-DNA conjugates. Three different chromophores, 6-carboxy-4,5'-dichloro-2,7'-dimethoxyfluoresein (JOE), 6-carbxy-teramethylrhodamine (TAMRA), and 6-carboxy-X-rhodamine (ROX), were employed as the energy donor, mediator, and acceptor, respectively, based on their overlapping excitation and emission spectra. These chromophores were attached to the 5'-termials of 10mer oligo-DNAs with different sequences. The conjugates were mixed with matrix oligo-DNA (30mer) consisting of complementary sequences for the conjugates in order to construct a sequential JOE-TAMRA-ROX array (chromophore array) in a DNA duplex with 10 residues separating each chromophore component. Vectorial photoenergy transmission along the DNA helix axis by fluorescence resonance energy transfer (FRET) in a sequential chromophore array was observed and analyzed by time-resolved fluorescence spectroscopy and lifetime measurements using a femtosecond pulse laser system. The results suggest a FRET occurs on a picosecond scale between the donor chromophore and the acceptor chromophore through a mediator chromophore via a multi-step FRET over the molecular assemblies (two helical pitches, 68 Å). In addition, by introduction of donor chromophore (Fluorescein, Flu) at certain position of DNA duplex (20mer) and acceptor chromophore (hexachrolofluorescein, Hex) at terminal of 'DNA duplex, distance dependence of FRET between the chromophores was investigated. Moreover, by introduction of 2-5 donor chromophore (Flu) at certain position of DNA duplex and acceptor chromophore (Hex) at terminal of DNA duplex, photo-harvesting effects resulted from energy migration was also investigated. Photo-harvesting effect was observed.