Perhaps an AA's isomer / isomerization is encoded in its codon

[Seagat2011]

Perhaps at a very fundamental level these AAs are actually a family of pre-isomerized blocks, eg

Typtophan/Tryp/W T:G:G ==> T.1:G.0:G.0 ( RANGE : (D) T.0:G.0:G.0 … (L) T.1:G.0:G.0 )

..this would make folding readily predictable due to only that isomer having been encoded into the protein chain.

(I hope this makes sense; i'm not quite sure with the terminology)