Pressure perturbation calorimetry instruments and methods

A method of determining a change in volume occupied by a target molecule as the molecule transitions from a first structure to a second structure in response to a change temperature, the method comprising:

• (a) providing a first liquid holder containing a solution comprising a plurality of target molecules, and a second liquid holder containing a liquid in which no target molecules are present;
• (b) at each of a plurality of temperatures that span a range in which the target molecules transition from the first structure to the second structure,
• (i) applying a pressure perturbation to the solution in the liquid holder and to the liquid in the second liquid holder at that temperature;
• (ii) determining a differential heat effect between the first and second liquid holders in response to the pressure perturbation;
• (iii) calculating, from the differential heat effect, the heat effect of the target molecule in response to the pressure perturbation;
• and
• (iv) determining, from the calculated heat effect at that temperature, the value of a specific property of the substance at that temperature, said specific property being a function of the thermal coefficient of expansion of the target molecules;
• and
• (c) from the values of said specific property at the plurality of temperatures, calculating a change in volume occupied by the target molecule.