A novel label-free sensitive detection method by employing a novel sensitive charge sensor is provided. Dissociation constant information is provided by a simple measurement of the dissociation of the target molecule form the target's receptor. The later process is affected by a novel system and its configuration as described herein. Basic objectives are to provide a drug discovery and characterization system that is an improvement over the current state of the art, low cost, highly sensitive, accurate, fast and easy to use. This invention involves both a physical system and a methodology.