 we 
 report the discovery of hd5-cd , an unprecedented c2-symmetric -barrel - like covalent dimer of the 
 cysteine - rich host - defense peptide human defensin 5 ( hd5 ) . 
 dimerization 
 results from intermonomer disulfide exchange between the canonical 
 -defensin cysii  
 cysiv ( cys5cys20 ) bonds located at the hydrophobic 
 interface . 
 this disulfide - locked dimeric assembly provides a new element 
 of structural diversity for cysteine - rich peptides as well as increased 
 protease resistance , broad - spectrum antimicrobial activity , and enhanced 
 potency against the opportunistic human pathogen acinetobacter 
 baumannii . 
Supplementary Material