  We report experimental observations on the effect of disorder on the phase
behavior of DNA-linked nanoparticle assemblies. Variation in DNA linker lengths
results in different melting temperatures of the DNA-linked nanoparticle
assemblies. We observed an unusual trend of a non-monotonic ``zigzag'' pattern
in the melting temperature as a function of DNAlinker length. Linker DNA
resulting in unequal DNA duplex lengths introduces disorder and lowers the
melting temperature of the nanoparticle system. Comparison with free DNA
thermodynamics shows that such an anomalous zigzag pattern does not exist for
free DNA duplex melting, which suggests that the disorder introduced by unequal
DNA duplex lengths results in this unusual collective behavior of DNA-linked
nanoparticle assemblies.
