Refinement and Truncation of DNA Aptamers based on Molecular Dynamics Simulations: Computational Protocol and Experimental Validation

Aptamers have proven useful for a wide variety of applications, such as drug delivery systems and analytical reagents for diagnosis or food safety control. Conventional aptamer selection methods typically produce sequences longer than necessary, which are optimized through a post-selection trial and error process to obtain the shortest-length sequence that preserves binding affinity. Herein, we describe a general strategy to obtain the tridimensional structure of DNA aptamers using a semiautomated molecular dynamics protocol, which serves as a guide to rationally improve experimentally selected candidates. Based on this approach, we designed truncated aptamers from previously described ligands recognizing different peptides and proteins, which are 20-35% shorter than the original candidates and present similar or even improved binding affinities. Moreover, we also discriminate between energetically similar secondary structures in terms of the energetic scoring of the molecular dynamics trajectories, and rationally explain the role of poly-thymine spacers in the (de)stabilization of the structure. This work demonstrates how a protocol for generating the aptamers tridimensional structure can accelerate their optimization for obtaining better analytical reagents and therapeutic agents.