Key terms associated with protein purity and validation. Purity
The percentage of the supplied product that is the protein of interest. Protein purity can be determined by multiple methods including SDS-PAGE, liquid chromatography (LC), and mass spectrometry (MS). The most accurate measurement of purity can be made using LC and MS together.
Animal-free
A protein is animal-free if has been produced without the use of any animal-derived materials.
Carrier-free
A protein is carrier-free if it provided to the customer without a carrier protein. Carrier proteins such as BSA are often added to proteins for stability; however, researchers often require carrier-free products for cell culture and in vivo use.
Endotoxin level
​Endotoxins are bacterial toxins which may be present as contaminants within protein products. The LAL method is a standard method of measuring endotoxins. Endotoxin levels tend to be higher in proteins expressed using E.coli than those expressed in other systems.