The molecule is colistin A in which each of the primary amino groups is converted to the corresponding aminomethanesulfonic acid, commonly by the action of formaldehyde followed by sodium bisulfite. It is a polymyxin, an amino sulfonic acid and a peptide antibiotic. It derives from a colistin A. It is a conjugate acid of a colistimethate A(5-).
[2-[(2S,5R,8S,11S,14S,17S,22S)-17-[(1R)-1-hydroxyethyl]-22-[[(2S)-2-[[(2S,3R)-3-hydroxy-2-[[(2S)-2-[[(6R)-6-methyloctanoyl]amino]-4-(sulfomethylamino)butanoyl]amino]butanoyl]amino]-4-(sulfomethylamino)butanoyl]amino]-5,8-bis(2-methylpropyl)-3,6,9,12,15,18,23-heptaoxo-11,14-bis[2-(sulfomethylamino)ethyl]-1,4,7,10,13,16,19-heptazacyclotricos-2-yl]ethylamino]methanesulfonic acid