Hallo,

I am looking for the isoelectric points of selenocysteine and pyrrolysin, but so far, I was unable to find them. All sources I have found so far state that the pIs for these two are "unknown" – but can this really be the case? They belong to the 22 proteinogenic amino acids, as proposed by IUPAC, surely someone must have measured the pIs at some point?

The pKas of the respective COOH/NH2 and the sidechains could also help, I could easily calculate the pIs with those, however, if possible, I would prefer the pIs.

So, please, does anyone have a source for one of those values?