MUC1 (UniProt ID P15941) synthetic glycopeptide fragment (Pro126-Gly149; UniProt position 126-149, aa length 24) from the variable number tandem repeat (TR) domain. The fragment contains tumour-associated carbohydrate antigen (TACA), Sialyl Tn or STn (Neu5Acα2-6GalNAcα-<i>O</i>-Ser) at Ser130 and Neu5Acα2-6GalNAcα-<i>O</i>-Thr at Thr131. The C-terminus is carboxylic acid.