October 22, 2020, 04:34:12 PM
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Topic: Need clarification of interpreting isothermal titration calorimetry readout  (Read 888 times)

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Offline woadleaves

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I am new to reading ITC readouts and I'm unclear on why, if little to no binding is occurring, there are still peaks.
I am looking at supp. fig. 3 in PMID: 23644599

To my understanding, peaks are the result of the energy the heater uses to maintain a constant temperature changing in response to the temperature of the sample cell changing when a binding event occurs. What I don't understand is why, in fig. 3C where little to no binding should be occurring, there are still severe peaks, which would imply an exothermic reaction is occurring--but between what? I would have expected that, if no binding is occurring, there would be no peaks. The titrant must be held at the same temperature as the analyte, I'm sure.

Can someone explain this to me?

(edited to better comply with rules for attaching images)

Offline Babcock_Hall

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Figure 3B is similar to what one hopes to see.  One thing that I noticed was that the y-scales in Figure 3C are much smaller than in Figure 3B.  Somewhat against my better judgment I will offer a tentative suggestion.  Suppose that there was a minor difference in pH or ionic strength between the two solutions.  This should produce an enthalpy of mixing.  However, I don't have an special knowledge of this paper.

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