Aptamers are nucleic acids that bind to a target molecule with high affinity and specificity, which are selected from systematic evolution of ligands by exponential enrichment (SELEX). Aptamers feature high affinity and specificity to their target molecule and a large structural diversity; biophysical tools, together with structural studies, are essential to reveal the mechanism of aptamers recognition. Furthermore, understanding the mechanism of action would also contribute to their development for therapeutic applications. Isothermal titration calorimetry (ITC) is a fast and robust method to study the physical basis of molecular interactions. In a single experiment, it provides all thermodynamic parameters of a molecular interaction, including dissociation constant, K_d; Gibbs free energy change, ΔG; enthalpy change, ΔH; entropy change, ΔS; and stoichiometry, N. The development of modern microcalorimeters significantly contributed to the expansion of the ITC use in biological systems. Therefore, ITC has been applied to the development of small therapeutic agents that bind to target proteins and is increasingly being used to study aptamer-target protein interactions. This review focuses on thermodynamic approaches for understanding the molecular principles of aptamer–target interactions.

适体是与靶分子以高亲和力和特异性结合的核酸，其选自通过指数富集（SELEX）的配体的系统进化。适体对它们的靶分子具有高亲和力和特异性，并具有很大的结构多样性。生物物理工具以及结构研究对于揭示适体识别机制至关重要。此外，了解作用机理也将有助于其在治疗应用中的发展。等温滴定热量法（ITC）是研究分子相互作用的物理基础的快速而可靠的方法。在一个实验中，它提供了分子相互作用的所有热力学参数，包括解离常数K _d。; 吉布斯自由能变化ΔG；焓变，ΔH；熵变，ΔS；和化学计量，N。现代微量热量计的发展极大地促进了ITC在生物系统中的使用扩展。因此，ITC已应用于与靶蛋白结合的小型治疗剂的开发，并且越来越多地用于研究适体与靶蛋白的相互作用。这篇综述着重于热力学方法，以了解适体-靶相互作用的分子原理。