We have examined the adsorption of different DNA sequences to mercaptoethanol-capped CdS quantum dots, ∼40 Å diameter, as a minimalist model for nonspecific protein−DNA interactions, and compared these results to what we have previously found for Cd 2+ -surface-rich dots of the same size (Mahtab, R.; Rogers, J. P.; Murphy, C. J. J. Am. Chem. Soc. 1995, 117, 9099). We find that neutralization of the surface leads to no detectable binding, based on our luminescence assay, for “straight” and A-tract oligonucleotides, while a crystallographically “kinked” sequence does still bind, but by a factor of 4 less than that observed for a divalent metal ion-rich surface. The binding constants for both surfaces are within the range of nonspecific protein−DNA interactions. The kinetics of binding are also monitored and are compared to nonspecific protein−DNA interactions for large DNA fragments. Issues of biopolymer static bending vs flexibility are also addressed with fluorescence resonance energy transfer experiments.
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Mahtab et al. (1996) studied this question.