Hi,
When doing ITC in our lab we have recently observed an osculating behaviour of the raw ITC data. We have tested different systems and the behaviour is the same (however, most visible with systems with a low heat detected). So the behaviour is somehow an artefact of the machine. If was considering if the syringe was slightly bended, but I wasn't expecting the result of a bended syringe to behave like this..
Have any of you seen such a behavior before?
Hi Frederik - I have occasionally seen such results from ITC - if you are using a MicroCal VP-ITC, there are some specific injection volumes that cause this pattern, due to the injection system. If you are using a MicroCal iTC200 this kind of effect may be due to specific experimental set up of injection volume, response time, and filter period, as well as the version of software you are using to collect the ITC data. This is not due to a bent syringe. Please email me the actual itc data files, to [email protected] this will help me evaluate the issue.
Regards, Verna
Hi Frederik – I sent you an email but it got blocked.
Looking at the information you provided, it looks like that “oscillation” in the apparent peak heights is due to a software artifact, on how the data are collected. You have an older version of the iTC200 control software, where using a 5 second filter has collected data at 5 sec, 10 sec, 15 sec, and data points every 5 seconds. If you notice the actual integrated areas are not that different in the deltaH plot.
You may not have noticed this effect with larger injection volumes, or different heat changes.
The current version of iTC200 software has the data sampling at more frequent intervals, this software should eliminate this issue.
You should contact your local Malvern Panalytical support group, they can let you know how to get the current version of ITC200 software.
I also notice there is a bit of noise in the ITC baseline, and that the heat changes at the end of the titration are not significantly different that the binding heat at the beginning. I can assist you further with troubleshooting, or you can contact your regional support team. Verna
Hi,
I realized that it might have something to do with the filter period. But do I need a new version of the software, or can I just use a shorter filter period (eg 2 sec?).
The noise in the baseline is expected since i have a reducing agent in the buffer, and the low change in heat is due to a weak interaction. Therefore there is a lot of protein in the syringe, which then causes the dilution heats in the end..
Hi Frederik!
I do have the same problem as yours while working with ITC200 and wondering if you found a solution for oscillation problem? I have carried out several injections including ligand to buffer and always get the same profile.
Regards,
Seda
Unfortunately, I have not found a solution. I will try to update the software that runs the instrument, since this has been suggested earlier. But changing settings have not solved the problem for me.
Which version of the software do you run?
Best
Frederik
I am using Origin 7.0.
I also have tried to change nearly all settings which did not work for me as well. But, once, I could able to get a good profile with same protein and ligand at the same conditions, and thus I am not sure if this is a software issue.
Regards,
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