While it is generally accepted that the functional tertiary structures formed by RNA cannot be replicated by a deoxy version of the same sequence, here we demonstrate conservation of function for a DNA homolog of an RNA aptamer. Using fluorescence anisotropy experiments, this work demonstrates that the all-DNA version of the RNA dopamine aptamer is able to bind dopamine with improved affinity and similar specificity relative to the RNA aptamer. Mutation studies suggest that the binding site is maintained in both structure types. These findings will help to elucidate what sequences and secondary structures allow for retention of function in both RNA and DNA. (C) 2009 Elsevier Inc. All rights reserved.