The degradation pathways leading to Asn degradation are quite different from those of Asp (e.g. Asn is hydrolised at pH 1-4, is stable between pH 4-5 and undergoes general buffer catalised Asu formation at neutral to alkaline pHs. Asp hydrolises the peptide bond at low pHs, gives rapidly rise to Asu at pH 4-5 and is more ´´stable´´ at neutral to alkaline pHs. Does somebody have references for similar process and/or comments with regard to the pyroglutamate formation from Glu and Gln OR a paper showing the dependence of Pyrogl. formation from Gln vs pH? Has moreover somebody heard or read of peptide bond bydrolysis at Glu under acidic conditions (like happens for Asp)? Thanks 1000