Published Research - Department of Chemistry


Date of this Version



Peptides. 2019 September ; 119: 170119. doi:10.1016/j.peptides.2019.170119


This work was funded by UNMC-startup funds (MC-S), National Institute of Health-NIGMS, Nebraska Center for Molecular Target Discovery and Development (1P20GM121316-01A1, PI: Robert Lewis, Project Leader, MC-S), and by the USA Department of Defense-Peer Reviewed Medical Research Program 2017 (W81XWH-18-1-0113, MC-S). This work was supported by funding from the Redox Biology Center (P30 GM103335, NIGMS, RP) and the Nebraska Center for Integrated Biomolecular Communication (P20 GM113126, NIGMS, RP). The research was performed in facilities renovated with support from the N.I.H. (RR015468-01). Some antimicrobial tests (as detailed in the SI) were performed by The Community for Antimicrobial Drug Discovery (CO-ADD), funded by the Wellcome Trust (UK) and The University of Queensland (Australia). The authors thank Dr. Andrew Dudley, Tom Bargar, and Nicholas Conoan (UNMC-Electron Microscopy Core Facility, EMCF) and Samantha Wall (UNMC-Flow Cytometry Research Facility, FCRF) for technical assistance. The EMCF and FCRF are supported by the Nebraska Research Initiative (NRI), the University of Nebraska Foundation, and the UNMC-Office of the Vice Chancellor for Research. FCRF is also supported by The Fred and Pamela Buffett Cancer Center’s through the NCI.


The rapid emergence of resistant bacterial strains has made the search for new antibacterial agents an endeavor of paramount importance. Cationic antimicrobial peptides (AMPs) have the ability to kill resistant pathogens while diminishing the development of resistance. Citropin 1.1 (Cit 1.1) is an AMP effective against a broad range of pathogens. 20 analogues of Cit 1.1 were prepared to understand how sequence variations lead to changes in structure and biological activity. Various analogues exhibited an increased antimicrobial activity relative to Cit 1.1. The two most promising, AMP-016 (W3F) and AMP-017 (W3F, D4R, K7R) presented a 2- to 8-fold increase in activity against MRSA (both = 4 µg/mL). AMP-017 was active against E. coli (4 µg/mL), K. pneumoniae (8 µg/mL), and A. baumannii (2 µg/mL). NMR studies indicated that Cit 1.1 and its analogues form a head-to-tail helical dimer in a membrane environment, which differs from a prior study by Sikorska et al. Active peptides displayed a greater tendency to form α-helices and to dimerize when in contact with a negatively-charged membrane. Antimicrobial activity was observed to correlate to the overall stability of the α-helix and to a positively charged N-terminus. Biologically active AMPs were shown by SEM and flow cytometry to disrupt membranes in both Gram-positive and Gram-negative bacteria through a proposed carpet mechanism. Notably, active peptides exhibited typical serum stabilities and a good selectivity for bacterial cells over