Substance is stainable with Ninhydrin, but does not appear on SDS when stained with very sensitive coomassie staining.
Coomassie apparently binds more avidly to basic amino acids (arginine, lysine), but this binding is not covalent.
Ninhydrin forms covalent bonds with most primary amines.
Thanks! So that is why I asked the question, because Ninhydrin also binds to primary amines. But you would say, if those primary amines are rather acidic or neutral coomassie doesn't bind well and that would explain the results.
Hi, interestingly enough, the exact mechanism by which coomassie binds the basic amino acids is apparently still not fully understood.
http://193.146.160.29/gtb/sod/usu/$UBUG/repositorio/10311883_Sapan.pdf
Maybe the ninhydrin works better because it forms a stable covalent complex with your compound while coomassie does not.
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