生物谷报道：在细胞核里有着记载遗传信息的DNA（脱氧核糖核酸），日本大阪大学产业科学研究所真嶋哲朗教授（光化学）的研究小组研究出在DNA中电流流动的情况。DNA的双螺旋链的直径大约在2纳米左右，利用这种纳米级的“电线”，可以制作出类似半导体的超微型电子设备。他们的研究成果发表在本周的《美国科学院学报》在线版上。
据朝日新闻报道，研究揭示了在DNA中电流流通的可能性，这一电子通道人们以前并不了解。真嶋教授的研究小组通过实验，首次确认了电流并非在双螺旋链通过，而是在两条链中间的盐基进行传导。
研究小组在人造玻璃衬底上铺设了排列了10－100个盐基的DNA片断。在一端使用光增感剂，另一端放置荧光色素，玻璃衬底中间进行紫外线照射。于是，从光增感剂那端产生正电荷，并向另一端移动与荧光色素发生反应，便能观测到荧光消失的现象。根据4种盐基排列的顺序不同，电流流动的速度也会发生改变。（引自中国公众科技网）
原始出处:
Published online before print June 25, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0700795104
Chemistry
Biochemistry
Single-molecule observation of DNA charge transfer
( electron transfer | single-molecule fluorescence | SNP detection )
Tadao Takada, Mamoru Fujitsuka, and Tetsuro Majima *
The Institute of Scientific and Industrial Research (SANKEN), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
Edited by Jacqueline K. Barton, California Institute of Technology, Pasadena, CA, and approved May 21, 2007 (received for review January 29, 2007)
DNA charge transfer highly depends on the electronic interaction between base pairs and reflects the difference in the base composition and sequence. For the purpose of investigating the charge transfer process of individual DNA molecules and the optical readout of DNA information at the single-molecule level, we performed single-molecule observation of the DNA charge transfer process by using single-molecule fluorescence spectroscopy. The DNA charge transfer process, leading to the oxidation of the fluorescent dye, was explored by monitoring the on-off signal of the dye after the charge injection by the excitation of a photosensitizer. The photobleaching efficiency of the dyes by the DNA charge transfer specifically depended on the base sequence and mismatch base pair, demonstrating the discrimination of the individual DNA information. Based on this approach, the optical readout of a single-base mismatch contained in a target DNA was performed at the single-molecule level.
Fig. 1. DNA charge transfer detection system. (a) Photobleaching of the fluorescent dyes by DNA charge transfer. The NI and fluorescent dye (Fl) are represented by blue and red, respectively. The fluorescent dye is oxidized when the charge can freely migrate through DNA, leading to the photobleaching of the dyes. In the presence of the mismatch site, the charge transfer to the dyes is inhibited. (b) The positive charge injection (hole) process via A-hopping and the following charge transfer to the reporter fluorophore. Excitation of NI by UV light generates NI in the singlet excited state, which oxidizes the adjacentAbase to give the contacted ion pair. The positive charge on theAbase escapes from the ion pair and migrates to the nearestGthrough hopping between A bases to provide the charge separated state with a long lifetime. The hole injected into DNA migrates to the fluorescent dye, leading to the irreversible reaction of the reporter fluorophore.
