page_title: KinITC
section_title: The practical problems
hierarchical_section_title: KinITC / The practical problems
caption_attribution_description: Ænglisc: Simulated response curves obtained in an ITC experiments with the instrument response times varying from 0.5 s (red) to 9.5 s (blue) in steps of 1 s Français&#160;: Simulation des réponses obtenues dans une expérience ITC avec le temps de réponse de l'instrument variant de 0.5 s (rouge) à 9.5 s (bleu) par pas de 1 s
context_page_description: The method kinITC for kinetic Isothermal Titration Calorimetry is an extension of the classical ITC technique in view of obtaining kinetic information in addition to thermodynamic information. It has been described in full in, and in a simplified and less general form in. In short, kinITC allows obtaining with a single technique both the information obtained with classical ITC and with a technique like Surface Plasmon Resonance. In situations where a chemical reaction proceeds clearly through two successive kinetic steps, the major interest of kinITC is of being potentially more informative alone than ITC and SPR used jointly, but in a classical way. The experimental limitation for its successful application comes from the response time of the instrument, which prevents from obtaining kinetic information if the reaction proceeds too rapidly. It turns out that this is not so much a severe limitation for many reactions occurring with biological macromolecules. The kinITC method is thus quite appropriate in biology. Note that, as pionereed long time ago by J.
context_section_description: The previous analysis is a simplified one because the power signal Pₛ(t) given by equation (4) does not correspond to the actually measured power Pₘ(t). There are two reasons for that. First, neither the injection, nor the mixing of compound B are instantaneous. Second, the ITC instrument has also a finite response time τITC, which implies that a sudden heat signal Pₛ(t) delivered into the measurement cell will in fact give rise to an actually measured signal Pₘ(t) decreasing exponentially with a characteristic time τITC. Such a response is named the impulse response. These two complications can nevertheless be dealt with by using standard methods in signal processing. Essentially, the actual signal is obtained by a Convolution of the ideal signal with the impulse response function. This is exemplified with the influence of τITC on the shape of the actually measured signal Pₘ(t)(Fig. 2). The influence of all parameters can be visualized on kinITCdemo. 
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  The practical consequence of such a convolution is a smoothing of the actual signal (compare the sharp ideal response curves in Fig. 1 with the realistic response curves in Fig. 2). Importantly, the convolution operation "dilutes" the power response curve, but does not change its time-integral, which corresponds to the total heat evolved during the titration step.
caption: Fig. 2: Influence of τITC
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