Abstract
In view of an appreciable increase in resistance of Staphylococcus aureus to the conventional antibiotics, it is desired to develop new effective drugs. Antimicrobial peptides (AMPs) seem to be attractive candidates. In general, AMPs samples used for in vitro studies consist of a peptide, counter-ion, and water. The presence of the counter-ion could be significant as it affects peptide secondary structure and biological activity. The purpose of this study was to estimate the impact of counter-ion on antistaphylococcal activity of selected AMPs (CAMEL, citropin 1.1, LL-37, pexiganan, temporin A). To do this, three kinds of salts were prepared, namely, acetates, hydrochlorides, and trifluoroacetates. In addition, the hemolytic activity against human red blood cells (hRBCs) and cytotoxicity (HaCaT) were determined. The results indicate that there is a substantial difference between different salts, but the pattern is not consistent for the peptides. In general, the antistaphylococcal activity decreased in the order: CAMEL > temporin A > pexiganan > citropin 1.1 ≫ LL-37. The highest selectivity indexes were determined for CAMEL hydrochloride, pexiganan acetate, and temporin A trifluoroacetate. This study shows how important is to take into account the kind of counter-ions when designing novel peptide-based antimicrobials.
Highlights
Nowadays, the solid-phase synthesis is a popular method in organic chemistry, especially in peptide synthesis (SPPS)
Peptides used in this study were, CAMEL (Andreu et al 1992), citropin 1.1 (Wegener et al 1999), LL-37 (Larrick et al 1995), pexiganan (Ge et al 1999), and temporin A (Simmaco et al 1996)
The antistaphylococcal activity decreased in the order: CAMEL > temporin A > pexiganan > citropin 1.1 ≫ LL-37
Summary
The solid-phase synthesis is a popular method in organic chemistry, especially in peptide synthesis (SPPS). The most popular is Fmoc/tert-butyl chemistry where trifluoroacetic acid (TFA) is used for cleavage and final deprotection. It is used in RP-HPLC as an additive to mobile phase, e.g., for ion-pairing of basic side chains and N-terminus amino group (Chandrudu et al 2013; Mäde et al 2014). Antimicrobial peptides (AMPs) are the group of compounds that seem to be an alternative to the conventional antibiotics These evolutionally conserved molecules play a vital role in the innate immune systems of almost all organisms (Mansour et al 2014). For estimation of the influence of different counter-ions on antistaphylococcal activity, the trifluoroacetate, acetate, and chloride salts were prepared
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