Figure 1.

Eletron transfer pathway in Re-modified azurin. The red wiggly arrow represents the incident UV pulse that triggers the ET process, and the blue wiggly arrows represent the probe X-ray pulses and the emitted signals. The ET pathway (from the Cu(I) center via the tryptophan group to the Re(I) center) is marked by black arrows. The three X-ray chromophores in the system—Re, Cl, and Cu atoms—are shown in orange, green, and purple, respectively. Ball-and-stick structures represent the electron donor (Cu-complex), intermediate group (Cl-substituted Trp122), and acceptor (Re-complex). Other segments of the protein are represented by solid ribbons.