  We investigate the mechanisms underlying selective molecular recognition of
single heteropolymers at chemically structured planar surfaces. To this end, we
study systems with two-letter (HP) lattice heteropolymers by exact enumeration
techniques. Selectivity for a particular surface is defined by an adsorption
energy criterium. We analyze the distributions of selective sequences and the
role of mutations. A particularly important factor for molecular recognition is
the small-scale structure on the polymers.
