Can I use chemical shape indicators (CSI) other than TSP or DSS? I normally add compound X as an internal chemical shift reference, since TSP interacts with the proteins in the sample.
8 February 2016 Comments Off on Can I use chemical shape indicators (CSI) other than TSP or DSS? I normally add compound X as an internal chemical shift reference, since TSP interacts with the proteins in the sample. FAQ - Sample Preparation
Chenomx NMR Suite has three predefined compounds for use as a CSI: DSS, TSP and formate.
In addition, Chenomx NMR Suite also allows you to define your own custom CSI. To define your own custom CSI, you must create a calibration spectrum with known quantities of your custom CSI and a known quantity of one of the predefined CSIs.
This calibration to a predefined CSI is necessary because, the CSI serves not only as a shift reference, but also a line shape reference; the shape of the CSI peak is used to correct shimming issues in spectra and to calculate expected line widths for all compounds. The CSI peak is also used as an internal standard for quantification. All of this information must be correctly defined for our advanced library features.
It is possible that DSS or TSP can bind to certain species, typically proteins, causing broadening of the DSS/TSP resonance and complicating the calculation of expected line widths. Methods of compensating for this binding effect are available. For serum samples, ultrafiltration using 3 kDa molecular weight cutoff filters can remove proteins and large lipids, reducing or eliminating their binding effects on DSS and TSP.