The PsaF subunit of photosystem I in a type of algae called Chlamydomonas reinhardtii is crucial for fast electron transfer from plastocyanin and cytochrome c6 to photosystem I. This was discovered through experiments using cross-linking techniques and flash absorption spectroscopy. In C. reinhardtii, both plastocyanin and cytochrome c6 can efficiently reduce P700+ with unique kinetics, taking only 3 μs to do so.