Synthesis and Surface Activity of Cationic Amino Acid‐Based Surfactants in Aqueous Solution

Abstract

I studied the possibility of using amino acid-based surfactants as emulsifiers at the same time as preservatives. Fourteen lipopeptides were synthesized employing a solid phase peptide synthesis procedure. All compounds were designed to be positively charged from +1 to +4 and acylated with fatty acid chain—palmitic and miristic. The surface activity of the obtained lipopeptides was tested using a semi-automatic tensiometer to calculate parameters describing the behavior of lipopeptides in the air/water interface. Such parameters as CMC, surface tension at the CMC point (σ CMC), effectiveness (π CMC), and efficiency (pC20) were measured. Emulsifying properties of all lipopeptides were also examined. The studies reveal that the surface active properties of synthesized compounds strongly depend on the length of alkyl chains as well as on the composition of amino acid polar heads. The critical micelle concentration decreases with increasing alkyl chain length of lipopeptides with the same polar head. The effectiveness and efficiency decrease when the number of amino acids in the polar head increases. All lipopeptides established a very weak emulsification power and created unstable water/Miglyol 812 and water/paraffin oil emulsions. Results suggest that lipopeptides cannot be used as emulsifiers; nonetheless, it is possible to use them as auxiliary surfactants with disinfectant properties in combination with more potent emulsifiers.

Double-Headed Cationic Lipopeptides: An Emerging Class of Antimicrobials

“…As expected, the critical aggregation concentration ( CAC ) values increased in the homologue series, i.e., Lys, Orn, Dab, and Dap, with a linear relationship of log CAC vs. number of methylene groups in the side chain of palmitoylated residue ( Figure S3, Supplementary Materials ). A comparison of the result obtained for K(K C16 )K-NH 2 with that for C 16 -KKK-NH 2 [ 22 ] showed that the transfer of the palmitoyl chain from the N -terminus of the peptide chain to the ε- N -amine group of the central lysine increased the CAC from 4.8 to 5.4 mM. The modification of the acyl chain position separated the positive charge centers located on the lysine side chains, changed mutual arrangement of the headgroups relative to the hydrocarbon tails, and increased the cross-sectional area of the polar heads.…”

“…We speculate that due to large steric hindrance of the hydrophilic groups, the KK(X C16 )KK-NH 2 peptides undergo self-assembly at a concentration several times higher than that for K(X C16 )K-NH 2 counterparts. Our assumption is based on a study on the N -terminally palmitoylated lysine-based peptides [ 22 ]. The linear dependence of log CAC on the number of lysine residues ( Figure S3, Supplementary Materials ) allowed us to roughly estimate a CAC value for C 16 -KKKKK-NH 2 to be around 60 mM.…”

“…Green color indicates the bacterial cells with intact membranes, whereas red color indicates the bacterial cells with damaged membranes. Figure S3: ( A ) Log CAC vs. the number of lysine residues for the N -palmitoylated lysine-based peptides, based on the data from reference [ 22 ]; ( B ) Log CAC vs. the number of methylene groups in the side chain of palmitoylated residue (from Dap to Lys); ( C , D ) Self-diffusion coefficients vs. lipopeptide concentrations for penta- and tripeptides. Arrows indicate two breakpoints for K(O C16 )K-NH 2 analogue, relating to the premicellar and micellar states, Figure S4: Isothermal titration of 1.3 mM POPG to ( A ) 0.05 mM KK(K C16 )KK-NH 2 ; ( B ) 0.05 mM KK(O C16 )KK-NH 2 ; ( C ) 0.05 mM KK(Dab C16 )KK-NH 2 ; ( D ) 0.05 mM KK(Dap C16 )KK-NH 2 at 298 K. The lower curves represent the heat of reaction (measured by peak integration) vs. the lipid/lipopeptide molar ratio, Figure S5: Isothermal titration of 1.3 mM POPG to ( A ) 0.05 mM K(K C16 )K-NH 2 ; ( B ) 0.1 mM K(K C16 )K-NH 2 ; ( C ) 0.05 mM K(O C16 )K-NH 2 ; ( D ) 0.05 mM K(Dab C16 )K-NH 2 ; ( E ) 0.05 mM K(Dap C16 )K-NH 2 at 298 K. The lower curves represent the heat of reaction (measured by peak integration) vs. the lipid/lipopeptide molar ratio, Figure S6: Scheme of the solid phase synthesis of lipopeptides included in this study on the example of K(K C16 )K-NH 2 lipopeptide.…”

Antifungal Activity of Linear and Disulfide-Cyclized Ultrashort Cationic Lipopeptides Alone and in Combination with Fluconazole Against Vulvovaginal Candida spp.

“…Their mode of action is based on the permeabilization of the membrane bilayers, what leads to cell death [13][14][15]18 . They can exhibit plenty of biological properties, such as antibacterial, antifungal, antibio lm, antiadhesive, anticancer and surface activities 19 . On the other hand, USCLs can be noticeably lytic to erythrocytes and cytotoxic to normal human cells 13,15,18 .…”

Low temperature preservation of porcine semen: influence of short antimicrobial lipopeptides on sperm quality and bacterial load

“…Thus, the aim of the present study was to evaluate a holistic approach combining a low temperature, antibiotic-free storing procedure for boar sperm with the use of alternative antimicrobial agents. The applied substances were a group of seven short lipopeptides derived from the two amino acid derivatives Fmoc-Lys(Boc)-OH and Fmoc-Lys(Fmoc)-OH 16 , 17 . Short lipopeptides possess many of the qualities of the more in-depth studied AMPs stated above (amphipathic, positively charged, antimicrobially active) while being less cost- and time-consuming in production 18 .…”