A Versatile Approach to Noncanonical, Dynamic Covalent Single- and Multi-Loop Peptide Macrocycles for Enhancing Antimicrobial Activity

Abstract

Peptide oligomers offer versatile scaffolds for the formation of potent antimicrobial agents due to their high sequence versatility, inherent biocompatibility, and chemical tunability. Though many methods exist for the formation of peptide-based macrocycles (MCs), increasingly pervasive in commercial antimicrobial therapeutics, the introduction of multiple looped structures into a single peptide oligomer remains a significant challenge. Herein, we report the utilization of dynamic hydrazone condensation for the versatile formation of single-, double-, and triple-loop peptide MCs using simple dialdehyde or dihydrazide small-molecule cross-linkers, as confirmed by MALDI-TOF MS, HPLC, and SDS-PAGE. Furthermore, incorporation of aldehyde-containing side chains onto peptides synthesized from hydrazide C-terminal resins resulted in tunable peptide MC assemblies formed directly upon resin cleavage post solid-phase peptide synthesis. Both of these types of dynamic covalent assemblies produced significant enhancements to overall antimicrobial properties when introduced into a known antimicrobial peptide, buforin II, when compared to the original unassembled sequence.

Dynamic covalent polymers for biomedical applications

“…Later on, the development was expanded to also encompass simple dialdehyde or dihydrazide small-molecule cross-linkers, or even tetra-/hexa-functionalized oligomers. 155 Together with the cationic antimicrobial peptide buforin II, the dynamic covalent peptide-based polymers showed enhanced inhibition effects towards the growth of Gram-negative and drug-resistant bacterial strains. were assembled into various macrocyclic and oligomeric structures through hydrazine formation reactions.…”

Assembly of Linked Nanocrystal Colloids by Reversible Covalent Bonds

“…Rapid formation of self-links is consistent with the studies of kinetics of hydrazone formation. 58,62,97,98 The system is energetically driven toward bond formation so that both ends of each linker quickly attach to any nearby available ligands. As the simulations progress, the number of unique (or "effective") links between NCs gradually increases (Figure 5c) for the mixtures that aggregated.…”

Assembly of Linked Nanocrystal Colloids by Reversible Covalent Bonds

“…Rapid formation of self-links is consistent with the studies of kinetics of hydrazone formation. 58,62,97,98 The system is energetically driven toward bond formation so that both ends of each linker quickly attach to any nearby available ligands. As the simulations progress, the number of unique (or "effective") links between NCs Number of linkers (per NC) forming (b) a link between any two ligands, (c) an effective (unique) link between two NCs, (e) a self-link between two ligands on the same NC, and (f) a redundant link between two NCs.…”