Structure and activity of (2,8)-dicarba-(3,12)-cystino alpha-ImI, an alpha-conotoxin containing a nonreducible cystine analogue.

The alpha-conotoxins are potent and selective antagonists of nicotinic acetylcholine receptors (nAChR). Exploitation of these and other peptides in research and clinical settings has been hampered by the lability of the disulfide bridges that are essential for toxin structure and activity. One solution to this problem is replacement of cystine bridges with nonreducible dicarba linkages.