RESIDUE ABA 16 CONECT N 3 CA 1HN 2HN CONECT CA 4 N CB C HA CONECT C 3 CA O OXT CONECT O 1 C CONECT OXT 2 C HXT CONECT CB 4 CA CG 1HB 2HB CONECT CG 4 CB 1HG 2HG 3HG CONECT 1HN 1 N CONECT 2HN 1 N CONECT HA 1 CA CONECT 1HB 1 CB CONECT 2HB 1 CB CONECT 1HG 1 CG CONECT 2HG 1 CG CONECT 3HG 1 CG CONECT HXT 1 OXT END HET ABA 16 HETNAM ABA ALPHA-AMINOBUTYRIC ACID FORMUL ABA C4 H9 N1 O2