Abstract
In this work we report the mapping of the binding site of the only progesterone aptamer published to date, in an approach referred to as aptatope mapping. By linking the binding data obtained from microscale thermophoresis analysis to the structural differences on the ring structure of a range of steroids, we elucidated the moieties involved in aptamer-progesterone binding. This approach can be further exploited for the characterization of aptamer specificity and ultimately facilitate the development of aptamer-based assays depending on the desired specificity.