Picosecond dynamics of iron proteins.

The excitation of hemoproteins containing either Fe(2+) or Fe(3+) with a picosecond light pulse resulted in the bleaching and recovery of the iron absorbance bands within 6 psec. A new absorbance band also was observed whose formation and decay rate of less than 6 psec suggests that it is probably due to S(1)-->S(n) absorbance. The Soret band relaxation time is deduced to be approximately 0.5 psec whereas the free base hemoprotein does not show any of the above fast-decay characteristics. Therefore, there is a strong influence of the metal on the energy dissipation process.