Mikayama Takeshi, Iida Kouji, Suemori Yoshiharu, Dewa Takehisa, Miyashita Tokuji, Nango Mamoru, Gardiner Alastair T, Cogdell Richard J
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
J Nanosci Nanotechnol. 2009 Jan;9(1):97-107. doi: 10.1166/jnn.2009.j084.
The conductivity of a photosynthetic reaction center (RC) from Rhodobacter sphaeroides was measured with conductive atomic force microscopy (CAFM) on SAM-modified Au(111) substrates. 2-mercaptoethanol (2ME), 2-mercaptoacetic acid (MAC), 2-mercaptopyridine (2MP) and 4-mercaptopyridine (4MP) were prepared as SAM materials to investigate the stability and morphology of RCs on the substrate by using near-IR absorption spectroscopy and AFM, respectively. The clear presence of the three well known RC near-IR absorption peaks indicates that the RCs were native on the SAM-modified Au(111). Dense grains with various diameters of 5-20 nm, which corresponded to mixtures of single RCs up to aggregates of 10, were observed in topographs of RCs adsorbed on all the different SAM-modified Au(111) substrates. The size of currents obtained from the RC using a bare conductive cantilever were produced in the following order for SAM molecules: 2MP > 2ME > 4MP > MAC. A clear rectification of this current was observed for the modification of the Au(111) substrate with the pi-conjugated thiol, 2MP, indicating that 2MP was effective in both promoting the specific orientation of the RCs on the electrode and electron injection into the RC. Cyclic voltammetry measurements indicate that the 2MP is better mediator for the electron transfer between a quinone and substrate. The current with 2MP-modified cantilever was twice as high as that obtained with the Au-coated one alone, indicating that 2MP has an important role in lowering the electron injection barrier between special pair side of RC and gold electrode.
利用导电原子力显微镜（CAFM）在自组装单分子层（SAM）修饰的Au(111)基底上测量了球形红杆菌光合反应中心（RC）的电导率。分别制备了2-巯基乙醇（2ME）、2-巯基乙酸（MAC）、2-巯基吡啶（2MP）和4-巯基吡啶（4MP）作为SAM材料，通过近红外吸收光谱和原子力显微镜（AFM）分别研究了RC在基底上的稳定性和形态。三个众所周知的RC近红外吸收峰的清晰出现表明RC在SAM修饰的Au(111)上是天然存在的。在吸附于所有不同SAM修饰的Au(111)基底上的RC的形貌图中，观察到直径为5-20nm的各种致密颗粒，这些颗粒对应于单个RC直至10个聚集体的混合物。对于SAM分子，使用裸导电悬臂从RC获得的电流大小顺序如下：2MP > 2ME > 4MP > MAC。在用π共轭硫醇2MP修饰Au(111)基底时，观察到该电流有明显的整流现象，这表明2MP在促进RC在电极上的特定取向以及电子注入RC方面都是有效的。循环伏安法测量表明，2MP是醌与基底之间电子转移的更好的媒介。用2MP修饰的悬臂获得的电流是单独使用金涂层悬臂获得的电流的两倍，这表明2MP在降低RC特殊对侧与金电极之间的电子注入势垒方面具有重要作用。
