Ultrafast anisotropy measurements on charge transfer dynamics in plastocyanin

Using a blue copper protein, plastocyanin, we have studied protein dynamics associated with optical excitation of the charge-transfer band of plastocy anin by ultrafast pump-probe measurements. In this study we show the first clear evidence of a coherency of the protein motion that is induced by the charge-transfer reaction. The formerly observed low-frequency vibrational m ode (33 cm(-1)) is attributed to the coherent motion of the protein by the anisotropy measurement. In this charge-transfer reaction, not only stochast ic process, but coherent motion of protein is revealed to play a key role i n the reaction.