Small structural changes in the vicinity of
ASP-96 may lead to a significant decrease in its pK in the N state.
in the relative energies of protonation states (as calculated from structural
changes in the photo-cycle)
the vectoriality of proton transfer. No need for change of accessibility during
of the cycle (O -> BR) may involve proton transfer from
ARG-82 to the release group and subsequent re-protonation of ARG-82 from
protonation state of the O-intermediate can be reproduced by assuming BR-like
structure in the Schiff
base region and
M-like in the release group region.