Ultrafast electron transfer of different vibronic states in flavodoxin

Understanding the ultrafast electron transfer (ET) processes involving various vibronic excitation in biological systems remains challenging and requires well-defined model proteins for in-depth studies. In this work, we selected three types of mutants with different ET lifetimes in flavodoxin to explore the excitation dependence of the photo-induced ET dynamics. For the ultrafast ET processes within the time window of intramolecular vibrational relaxation, with increasing excitation energies, we observed no change of ET lifetimes but with higher vibrational excitation in products, both of which can be attributed to the unique nature of ultrafast ET. For the slower ET, we did not find any dependence of product vibration excitation relative to the initial different excitation due to the complete vibrational relaxation. These results strongly indicate the vibrational energy can be propagated to the subsequent reactions during ultrafast ET processes.