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

在非共价分子组装系统中，使用发色团/寡聚DNA偶联物构建了三种发色团的特定顺序排列，这些发色团的距离大约等于DNA双链的一个间距（34 Å）。根据三种不同的发色团，6-羧基-4,5'-二氯-2,7'-二甲氧基荧光素（JOE）、6-羧基-teramethylrhodamine （TAMRA）和6-羧基- x -rhodamine （ROX）的重叠激发和发射光谱，分别作为能量供体、介质和受体。这些发色团以不同的序列连接在10mer寡聚dna的5'端。将偶联物与由偶联物互补序列组成的基质寡聚DNA （30mer）混合，在DNA双工中构建顺序的jo - tamra - rox阵列（发色团阵列），每个发色团成分有10个残基分离。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，观察和分析了序列发色团阵列中荧光共振能量传递（FRET）对DNA螺旋轴的矢量光能传输。结果表明，在供体发色团和受体发色团之间，通过中介发色团，通过分子组装（两个螺旋间距，68 Å）上的多步FRET发生在皮秒尺度上。此外，通过在DNA双链（20mer）的特定位置引入供体发色团（Fluorescein, Flu）和在DNA双链末端引入受体发色团（hexachrolofluorescein, Hex），研究了两个发色团之间FRET的距离依赖性。此外，通过在DNA双链的特定位置引入2-5个供体发色团（Flu）和在DNA双链末端引入受体发色团（Hex），研究了能量迁移引起的光收集效应。观察到光收获效应。

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.