User`s manual

68 Chapter 6: Sample Experiments
Calorimetry Sciences Corp.
CSC 5300 N-ITC III 69
User’s Manual
Chapter Seven: Troubleshooting
Minimizing Blank Corrections
There will always be blank corrections for experiments. However, minimizing the blank
correction can greatly improve experiments. Even when injecting water into water there
will be some heat produced due to viscous mixing. The viscous mixing heat is determined
by many factors.
There are several steps that can be taken in order to minimize the dilution heats and
hence the need for blank titrations. Ligand solution should always be made up in the
same dialysis buffer used for the protein. If the ligand is also a protein then it should be
dialyzed in the same buffer. Less concentrated solutions also have lower dilution heats
and should be used when possible.
Operation Away from Ambient Temperature
The N-ITC III is designed to perform over a wide temperature range. When operating the
N-ITC III away from ambient temperature it is important to allow adequate time between
injections for the titrant to equilibrate to the calorimeter temperature before injection.
Thorough degassing of the titrant is especially important when operating above the
ambient temperature.
Stirring Speeds
Adequate stirring is required in order to have rapid mixing of the titrant upon injection,
but excessive stirring will result in noisy baselines. Generally, a stirring speed of 150-200
rpm is appropriate.