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Shenandoah uses a combination of methods to determine protein purity and quantity. These methods are protein dependent and can include SDS-PAGE, analytical HPLC analysis, Western blotting, A280 spectrophotometry, and ELISA analysis. Due to the subjective nature of some methods and the inability to objectively distinguish between 96% and 97% purity, Shenandoah documentation denotes purity acceptance criteria and results as ≥90% or ≥95%.
Our primary method of determining product purity is by Coomassie Blue stained 4-20% Tris-Glycine SDS-PAGE gel under reducing and non-reducing conditions. SDS-PAGE analysis is an excellent tool for determining proper protein folding and sample purity.
Example of Coomassie-stained SDS-Page gel:
Analytical high-performance liquid chromotography (HPLC) is used to identify the quality and quantity of the protein sample.
Western blotting is a great tool that Shenandoah uses to validate product purity and protein identity. The protein samples used in western blotting are mainly mammalian-produced proteins that undergo multiple post-translational modifications, such as glycosylation. These types of proteins tend to run as a smear or multiple bands on a Coomassie-stained SDS-PAGE gel and require further validation using the western blot assay.
Example of Western Blotting Data: