“…Since the E'0 values (pH 7) of iron porphyrins are positive (i.e., the removal of electrons from such compounds represents an endergonic process), the release of energy in transferring electrons from one "positive" system to another more "positive" must be due 6 "Unter Reduktion versteht man chemische Vorgange in der Materie, die mit Energiebindung, unter Oxydation solche, die mit Energiea&ja&e einhergehen." (142). to the reduction of the most "positive" system.…”