VP-ITC MicroCalorimeter User’s Manual
at or below the experimental temperature. If the loaded sample is at a higher temperature, there
will be a long equilibration period before the experiment will begin. (See page 78 more
information).
Reference Power (
µ
Cal/sec.)
Throughout an ITC experiment, a small constant amount of power (equal to the value entered
here) is continuously supplied to the offset heater of the reference cell. This causes the DP
feedback system to become positive to supply compensating power to the sample cell that will
equilibrate the temperatures. During an experiment the DP baseline will equilibrate near the value
entered in this box. The reference power setting is often referred to as the baseline setting.
The best choice for the reference power setting will be determined by the anticipated size and
direction of the titration peaks. Large exotherms will require a large reference power setting (ca.
30 uCal/sec.) and large endotherms will require a very small reference power setting (ca. 2
uCal/sec.).
Initial Delay (sec.)
Enter the time, in seconds, from the start of the experimental data collection till the time of the
first injection. The minimum time allowed by VPViewer for this parameter is 60 seconds, this is
necessary to establish a baseline prior to the first injection.
Syringe Concentration (mM)
Enter the mM concentration of the solution in the syringe.
This value is stored in the data file header and used in Origin for ITC data analysis. This value is
used only during data analysis and an entry is not required to perform an experiment. If the value
is not entered or entered incorrectly the user will be warned, but it can also be entered/edited in
data analysis.
Cell Concentration (mM)
Enter the mM concentration of the solution in the cell.
This value is stored in the data file header and used in Origin for ITC data analysis. This value is
used only during data analysis and an entry is not required to perform an experiment. If the value
is not entered or entered incorrectly the user will be warned, but it can also be entered/edited in
data analysis.
Stirring Speed
Select the desired stirring rate from the drop down list (310 is recommended for most ITC
experiments).
There are 5 stirring rates available, they are ca. 0, 270, 310, 500 and 580 RPM (revolutions per
minute). The exact stir rate for your instrument is measured and the value is entered into the
software. The default rate of ca. 310 RPM has been found to be desirable for most experiments.
If the solution in the sample cell contains suspended particles (e.g. agarose beads), faster stirring
will be necessary.
Please refer to the section
Selecting the Proper Stirring Rate
starting on page
22
