[{"from": "human", "value": "Provide a brief overview of this molecule. [C][C@H1][C@@H1][Branch2][#Branch1][P][C@H1][Branch2][#Branch1][N][C@H1][Branch2][Branch1][=N][C@H1][Branch1][Ring2][O][Ring1][=Branch1][O][C@@H1][C@@H1][Branch2][Ring2][S][C@H1][Branch2][Ring2][=Branch1][C@@H1][Branch1][#Branch2][O][C@@H1][Ring1][=Branch1][C][=Branch1][C][=O][O][O][C@@H1][C@H1][Branch1][#C][C@@H1][Branch1][O][O][C@@H1][Branch1][Branch1][C@@H1][Ring1][=Branch1][O][C][O][O][N][C][=Branch1][C][=O][C][O][C][=Branch1][C][=O][C][O][O][C@H1][C@@H1][Branch2][Ring1][Branch1][C@@H1][Branch1][N][C@H1][Branch1][Branch2][C@@H1][Branch1][Ring2][O][Ring1][=Branch1][C][O][O][C][=Branch1][C][=O][C][O][O][O]"}, {"from": "gpt", "value": "The molecule is a polysaccharide derivative comprised of a [2)-alpha-L-Rhap(III)-(1->2)-alpha-L-Rhap(II)-(1->3)-beta-D-GalpA-(1->3)-beta-D-GalpNAc-(1->] tetrasaccharide repeat modified by the addition of an acetyl group to either O-3 or O-4 of many of the Rha(III) residues (60% to O-3; 30% to O-4). The structure provided is representative of that in Shigella flexneri serotype 6 and shows the most common repeating unit. It has a role as an antigen."}]