In plants, cytochrome f gives electrons to plastocyanin, which then transfers them to photosystem 1. Scientists used nuclear magnetic resonance to study the structure of the cytochrome f/plastocyanin complex. They found that the heme iron of cytochrome f and the copper ion of plastocyanin are close together, allowing fast electron transfer. The copper ligand His87 is near the iron ligand Tyr1, suggesting electron transfer happens through a hydrophobic patch on plastocyanin. The complex also relies on electrostatic interactions for efficient electron transfer.