Observation of ultrafast Q-band fluorescence in horse heart cytochrome c in reduced and oxidized forms.

The dynamics of fluorescence from horse heart cytochrome c is investigated in reduced (ferrous) and oxidized (ferric) forms by a streak camera and an up-conversion technique under B-band excitation at 415 nm. In the reduced form, we found the Q-band emission at 550 and 600 nm originated from the S(1) state in a short time range. A very broad continuum observed from 440 to 660 nm had only shown a slow component and was assigned to impurity. In the reduced form, the lifetime of S(1) was determined to be 120 fs by using the up-conversion technique. In the oxidized form, the S(1) lifetime was estimated to be 21 fs. These values are consistent with the values estimated from the quantum yield in order of their magnitude.