'Changed how 6 PI3K sites on ErbB3 dimers are handled.  Assumed
sequential binding for all of the six sites (most likely not what's
happening) but assigned individual parameters to each sequential binding
so that hopefully an effective rate constant can be fitted.  Also
assigned separate catalytic rates to complexes with 1 to 6 PI3K
molecules bound.  All of these simplifications used to try to cut back
on species.  Model runs and and species have been quickly checked (still
need a thorough species check).  Species: 1172. Parameters: 226.'