Electron Transfer Reactions of C-type Cytochromes with the Self-Assembled Monolayer of the Optically Active CoIII Complex on Au
Transactions of the Materials Research Society of Japan
In order to obtain the structural information around the active site of three c-type cytochromes ( cyt c from horse heart, cyt c2 from Rhodospirillum rubrum, and cyt cm from Alcaligenes xylosoxidans'G'IFU •051) in aqueous solution, we studied their redox behaviors by use of the densely packed monolayer of the (S)-phenylalanine-containing Corn complex. In the case of cyt c, no redox wave was observed, which agrees with the previous report· that the heme is buried inside of the protein. In
... protein. In contrast, the redox wave of cyt c 2 was clearly observed, which coincides with the fact that the heme positions at the protein surface. Interestingly, in the cyclic voltammogram of cyt c 2 , a splitting of the wave was detected, which was elucidated to be attributable to the protonation/deprotonation ofHis42 imidazole of the protein. Cyt cm, of which the structural information has still not been revealed, gave the redox wave without splitting. In the light of the results of cyt c and cyt c 2 , this redox behavior indicates the existence of two structural characteristics for cyt c 553 : (i) the heme is probably located near the protein surface, and (ii) there is no confoon.atiQnal c;llange caused by the protonation. differences were detected. as the different redox behaviors through simple electrochemical measurements.