Compound QC at ZoBio by NMR: Structure Confirmation and Solubility Assay
Just as good quality data is essential to draw the right conclusions from experiments, so are good quality compounds. There are many ways to assess compound quality and one technique we regularly use for this purpose at ZoBio is NMR.
We start by dissolving incoming compounds in d6-DMSO to generate stock solutions for use in various assays. The advantage of using d6-DMSO is that the same stock can not only be used for biochemical and SPR assays, but also for ligand- or protein observed NMR. This way, we reduce batch to batch variance and generate consistent data over the various assays.
The simplest form of QC is a 1H NMR spectrum of the stock in d6-DMSO. This data is used to confirm compound identity and structure, i.e. is the compound in the vial the correct compound? Additionally, we can see if there are any proton containing impurities. We also regularly determine compound solubility in aqueous buffer by NMR. To this end, a sample of the d6-DMSO stock is diluted into a deuterated phosphate buffer at pH 7.2 containing NaCl and an internal standard. The solubility of the compound in buffer can be calculated by comparing the NMR resonances of the compound to those of the standard. The advantage of this assay is that it is insensitive to impurities like silica and dust and even upon partial precipitation of the compound, we can still calculate the amount of compound remaining in solution. Additionally, we can also check the stability in buffer, as many compounds can hydrolyze or oxidize in aqueous solution. This solubility data is then directly used to determine the appropriate concentration to use for each compound in subsequent assays. If you want to know more about NMR QC and solubility assays, don’t hesitate to contact us.