a thiol + 2-aminoprop-2-enoate => an S-substituted L-cysteine
a thiol + 2-aminoprop-2-enoate => an s-substituted l-cysteine
a thiol + 2-aminoprop-2-enoate => an S-substituted L-cysteine
a thiol + 2-aminoprop-2-enoate => an s-substituted l-cysteine