Monolayers were loaded with colloidal gold
either by sonication (see below) or by uid-phase uptake. For uid-phase uptake, approximately 24 hours before
the experiments the culture medium was supplemented
with the colloidal gold suspension either at approximately
3300 particles per cell or at 330 particles per cell. Im- mediately before the experiments, free gold was removed
by rinsing the monolayers in Hank’s Balanced Salt Solution
(HBSS) without sodium bicarbonate or phenol red, buffered at pH 7.4 with 10 mM HEPES (both from Sig- ma, St. Louis, MO