Abstract: A method of screening a test agent for its ability to cause a thermodynamic change in a cell-free sample, comprising the steps of: i) measuring the temperature of said sample using electrothermometry; ii) contacting the sample with said test agent; iii) measuring the temperature of the sample resulting from step (ii) using electrothermometry; and iv) comparing the temperature obtained in step (i) with the temperature obtained in step (iii), wherein temperature measurement steps (i) and (iii) are conducted using a non-invasive electro thermometric method.