ich can be accommodated 
without overlap with the van der Waals surface of any atom.  The optimization
is achieved by a Monte Carlo simulated annealing procedure.  This method was
initially chosen to avoid becoming trapped in local "minima" but has
subsequently proved to be useful in follow alternative routes through channels
with a complex internal cavity, such as annexin V (Smart, Wallace and
Goodfellow, 1993).  Once the largest sphere which can be accommodated on a
particular plane is found a small displ