Proteins can be reduced before being run on an SDS-PAGE gel. In reducing conditions β-mercaptoethanol (β-ME or 2-ME) or dithiothreitol (DTT) is added; this reduces the disulfide bridges in proteins so that when they are run on the gel, they are better separated by size. Many of our growth factors are disulfide-linked dimers so running non-reduced proteins on the same gel as reduced proteins allows confirmation of the correct dimeric state.
As standard, we run all 3ug and 7ug of our recombinant proteins in reduced and non-reduced conditions to ensure there are no contaminants, aggregates or degradants. We also test our recombinant proteins by quantitative densitometry to ensure all our proteins are >98% pure.
Why are your proteins stated 98% pure, what is the other 2%?
We believe our proteins are >99.9% pure. However, due to limitations of gel staining and densitometry, there is an inherent error of +2%, which means that we can only ever state the limit of the assay, or >98% purity. To ensure purity, we always run a gel with a large amount of protein (7 ug) to ensure that we can detect any other proteins, aggregates, or degradation products. The SDS-PAGE results are validated with mass spectrometry analysis for every lot of protein manufactured.