Biosensors are among the most important biomolecular tools used to detect and quantify molecules and molecular processes both in vitro and inside the cell. Among the different types of biosensors in use, the most common category takes advantage of conformational changes that are induced in a biomolecule upon its binding to a specific target. So far, biosensors have been successfully designed using all possible natural polymers (DNA, RNA, proteins), using many different conformational change-based mechanisms and many different assays (absorbance, fluorescence, luminescence, electron transfert…). However, up to date, very few or no studies have focused on the implication and importance of the thermodynamic of the sensor. In the present work, we describe the equations that predict how a sensor's dynamic range, detection limit, and specificity will be affected by its thermodynamic. As a proof of principle, here we show how the dynamic range and detection limit of a simple classic DNA molecular beacon can vary by more than 4 orders of magnitude by simply stabilizing the stem portion of its stem loop by increasing its G-C content. The same equations also predict how a sensor can be tuned to obtain the best specificity to distinguish between two targets that display similar affinities. These findings may be applicable to all conformation change-based sensors and will greatly help to enhance both the sensitivity and the dynamic range of all sensors presently in use.

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