methionine-81 and/or -8 of the transmembrane sialoglycoprotein , glycophorin a , have been specifically alkylated with 13ch3i to produce the sulfonium ion derivatives [ s- [ 13c ] methylmethionine-8 ] glycophorin a and [ s- [ 13c ] methylmethionine-8 and -81 ] glycophorin a .
C0025646
methionine
C0042889
methylmethionine