Kinetics and Thermodynamics of the Association of DNA Coated Colloids

We have investigated the aggregation kinetics and thermodynamics of complementary DNA coated particles as a function of DNA coverage. The streptavidin on our particles can accommodate 69800 biotinalated DNA which has 50 base pair double strands and 11 base sticky ends. For full 100\% coverage, the melting temperature, $T_m$, is 50.3 C. The transition width, $\Delta T$, is 0.8 C, and the characteristic aggregation time, $\tau$, is 4 minutes. For 2.5\% (40 times less) coverage $T_m$ = 22 C, $\Delta T$ = 5 C, and $\tau$ = 11 hours. A simple model which takes into account the number of DNA bonds and the multiplicity of their arrangements accounts for the full time and temperature dependence of the particle aggregation.