Utilization of kinITC in AFFINImeter
This application note describes how and when can kinetic information be retrieved from ITC power curves. The results shown here were obtained with programs developed with Mathematica from Wolfram Research, which was employed to implement and validate the method. The underlying algorithms were all introduced into AFFINImeter.
sponsored by Malvern Panalytical
Introduction
It is commonly thought that ITC is a typical thermodynamic technique that is not really suited to extract kinetic information. It is thus commonplace to oppose ITC to SPR since the latter is a kinetic technique par excellence. However, this is at best an oversimplification since ITC is based upon kinetic measurements. Indeed, the raw signal measured in any ITC experiment is a heat power (in µJ s-1 or µcal s-1), that is essentially the rate of heat production, and not the heat itself evolved in a reaction. Obviously, this rate of heat production is directly related to the kinetics of the reaction taking place in the measurement cell, which is the reason why a microcalorimeter is potentially much more than merely a ‘heat-meter’. This is in line with the common observation that there are systems showing after each injection a quick return to baseline, that is a quick equilibration time, and others, on the contrary, showing slow, and even very slow, return to baseline. It should not come as a surprise, therefore, that ITC has already been used to derive kinetic information. Many readers, however, will probably be surprised to learn that the first “compensation-mode” calorimeter (the ancestor of the MicroCal VP-ITC and MicroCal ITC200 instruments) was devised in 1924 and used first to measure the heat power produced by flies [1, 2]. Therefore, the first “compensation-mode” calorimeter was used for what we now call a kinITC experiment.
