This is the photosynthetic reaction center of Rb. sphaeroides, one of the proteins,
that I did research on in the past, in particular with accumulated photon echo
techniques.
Click on the picture to see a chime presentation of the Reaction center of
Rps. viridis, which is distinguished from Rb. sphaeroides by a tightly attached Cytochrome
unit and whose absorption is red-shifted in comparison.
Note, that you need the Chime Plug-in
to do this. It is easy to install and truly worth doing !