Namely, Q6R/G7K/E10Y and Q6R/G7R/E10Y, showed no antibiofilm activity (Table 1; BIC-2, 25 M). As currently observed for the double analogues, combining single-amino acid substitutes with enhanced antibiofilm activities doesn’t necessarily result in further-increased antibiofilm activity and, on the contrary, could absolutely abolish it. Because the highest antibiofilm activity was observed for the Q6R/ G7K analogue, we synthesized this OSIP108 analogue, at the same time as a cyclic derivative of this double-substituted analogue (which in view of potential applications is expected to be more steady than the corresponding linear peptide) with 99 purity, as previously described (14). The antibiofilm activity on the 99 pure doublesubstituted Q6R/G7K analogue was not different from that from the crude version (BIC-2, 1.5 0.two M versus 1.0 0.0 M, respectively [means regular errors on the means]). Additionally, in line with our earlier findings that cyclization is just not favorable for OSIP108 antibiofilm activity (14), the cyclic Q6R/G7K analogue showed no antibiofilm activity (BIC-2, 25 M). Strikingly, the single-substituted OSIP108 analogues E10F, E10M, E10K, E10H, and E10R along with the double-substituted G7R/ E10Y and triple-substituted Q6R/G7H/E10Y OSIP108 analogues allowed paradoxical biofilm formation at larger concentrations ( 6.25 or 12.5 M) (data not shown). Paradoxical biofilm formation is defined as a resurgence of biofilm formation ( 50 relative to control therapy) at peptide concentrations above the BIC-2 (17). A comparable paradoxical effect of caspofungin has been observed on C. albicans biofilms and planktonic cells (17, 18); this effect was found to be related with many cell wall rearrangements and calcineurin-mediated signaling pathways in planktonic C. albicans cells (18, 19). Wiederhold and colleagues showed larger MKC1 expression in C. albicans planktonic cells treated with caspofungin concentrations major to this paradoxical growth phenomenon in comparison with fungicidal caspofungin concentrations (19). MKC1 encodes the central kinase of the C.5-Iodo-2-methylthiazole web albicans cell wall integrity (CWI) pathway (20).Formula of Perfluorohexyloctane We previously showed that OSIP108 activates the C.PMID:23543429 albicans cell wall integrity pathway (14). However, such a paradoxical biofilm effect was not observed for the native OSIP108. It remains to become elucidated irrespective of whether the OSIP108 analogues that induce this paradoxical development phenomenon in C. albicans biofilm cells induce the CWI pathway to a higher extent than native OSIP108 and whether or not this induction from the CWI pathway is responsible for the observed paradoxical biofilm impact. In conclusion, this study shows that site-specific amino acid substitutions can drastically alter the antibiofilm activity of OSIP108. Subsequent double and triple combinations of analogues with improved antibiofilm activities permitted us to pick OSIP108 with Q6R/G7K because the tested analogue with highest antibiofilm possible, with an eight.1-fold-higher activity against C. albicans biofilms. In view in the urgent clinical need to have for novel and much more valuable antibiofilm therapies, the OSIP108 variants with enhanced antibiofilm activities are valuable antibiofilm lead molecules.ACKNOWLEDGMENTSThis perform was supported by the European Commission’s Seventh Framework Programme (FP7/2007-2013) beneath grant agreement COATIM (project number 278425), Fonds Wetenschappelijk Onderzoek (FWO)– Vlaanderen (G.0414.09, W0.026.11N, and K220313N), Agentschap voor Innovatie door Wetenschap en Technologie (.
