Subpicosecond emission studies of bacterial reaction centers

The spontaneous emission of reaction centers from native and
mutated Rhodobacter sphaeroides and from wild type Chloroflexus
aurantiacus is investigated by fluorescence up-conversion with high
temporal resolution. The time constant of 0.9 ps previously
observed in transient absorption experiments on wild type reaction
centers of Rhodobacter sphaeroides does not appear in the emission
experiment. However, all investigated reaction centers display a
biexponential decay of the emission with time constants in the 2 ps
to 25 ps range. The experimental results are discussed within the
frame of different reaction models including a possible sample
heterogeneity or a transient electron transfer to the inactive
pigment branch.