  We examine the crystallization dynamics of nanoparticles reversibly tethered
by DNA hybridization. We show that the crystallization happens readily only in
a narrow temperature "slot," and always proceeds via a two-step process,
mediated by a highly-connected amorphous intermediate. For lower temperature
quenches, the dynamics of unzipping strands in the amorphous state is
sufficiently slow that crystallization is kinetically hindered. This accounts
for the well-documented difficulty of forming crystals in these systems. The
strong parallel to the crystallization behavior of proteins and colloids
suggests that these disparate systems crystallize in an apparently universal
manner.
