Influence of lipidation of GBV-C/HGV NS3 (513-522) and (505-514) peptide sequences on its interaction with mono and bilayers

Synthesis of Lipopeptides by CLipPA Chemistry

Lipidation of polypeptides with a fatty acid to form N-linked lipopeptides can be a time consuming process due to the need to mask other reactive function groups present on the side chains of amino acids. Cysteine Lipidation on a Peptide or Amino acid (CLipPA) technology enables the direct lipidation of unprotected peptides containing a free thiol group to afford S-lipidated lipopeptides. A generalized procedure for the synthesis of S-lipopeptides is described which facilities rapid preparation of tens of analogs of lipopeptides from a single thiolated polypeptide precursor.

Synthesis of Antimicrobial Lipopeptides Using the "CLipPA" Thiol-Ene Reaction

Cysteine Lipidation on a Peptide or Amino acid (CLipPA) technology provides a facile method for the lipidation of unprotected peptides containing a free thiol group by using a "click" radical-initiated thiol-ene reaction to effect addition to a vinyl ester. The methodology is highly versatile, leading to high conversion rates while maintaining excellent chemoselectivity and tolerance for a large variety of peptide substrates and functional groups. Herein we describe the simple general procedure for the synthesis of a focused library of bioactive S-lipidated antimicrobial peptides via late-stage derivatization using solution-phase CLipPA lipidation.

Orientation phase transitions of undissociated n-decanoic acid at the air/solution interface revealed by surface pressure and electric potential

The surface pressure (Π) and electric surface potential (ΔV) vs. concentration (c) isotherms of n-decanoic acid (DA) in 1 × 10^-3 mol/dm³ HCl were measured at the air/solution interface - the Π with a du Noüy ring, the ΔV with the vibrating plate (named also the dynamic condenser) method. The DA solutions fulfilled criterion of surface-chemical purity. The complementary Π-c and ΔV-c isotherms were jointly evaluated to obtain dependence of quotient of the effective dipole moment to the interface's permittivity, μ_⊥/ε_s, as a function of chosen adsorption ordinates such as the bulk concentration, c, partial molar area, A, and surface molar fraction of DA, X_DA^s. The crucial point for the analysis is knowledge of the surface excess (Γ) dependence on concentration (c). Since, experimental determination of a Γ-c course is problematic, so far, we used Γ-c courses calculated basing on different adsorption models (Gibbsian, the classical Frumkin' model and the Lunkenheimer' and Hirte' two state approach). Despite, the Γ-c courses determined basing on the different adsorption models differ significantly, the μ_⊥/ε_s dependences on different adsorption's ordinates (c, A or X_DA^s) revealed consistently three local μ_⊥/ε_s maxima of their height increasing with the adsorption coverage. The μ_⊥/ε_s change was recalculated into inclination angle (α_incl) of the total dipole moment vector (μ→) to the interface, assuming ε_s = 1. The μ_⊥/ε_s which reflects polarization orientation is an order parameter used by us for analysis of 2D phase transitions in the monolayer. The three μ_⊥/ε_s local maxima are ascribed by us to three 2D mono-phases, one transferring into the next one of the higher order in the sequence: liquid expanded (L1) → the liquid condensed tilted (L2) → the liquid condensed untilted (L2'). One inflection point appearing in the Π-A isotherm within the region between the μ_⊥/ε_s maxima 2 and 3 indicates that transition of the L2 into the L2' 2D phase is of the first order. Decrease of the μ_⊥/ε_s above the maximum 3 indicates transition into two phase regime by nucleation of aggregates (possibly in form of lamellas) within the L2' phase.

Penetration of milk-derived antimicrobial peptides into phospholipid monolayers as model biomembranes

Three antimicrobial peptides derived from bovine milk proteins were examined with regard to penetration into insoluble monolayers formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DPPG). Effects on surface pressure (Π) and electric surface potential (ΔV) were measured, Π with a platinum Wilhelmy plate and ΔV with a vibrating plate. The penetration measurements were performed under stationary diffusion conditions and upon the compression of the monolayers. The two type measurements showed greatly different effects of the peptide-lipid interactions. Results of the stationary penetration show that the peptide interactions with DPPC monolayer are weak, repulsive, and nonspecific while the interactions with DPPG monolayer are significant, attractive, and specific. These results are in accord with the fact that antimicrobial peptides disrupt bacteria membranes (negative) while no significant effect on the host membranes (neutral) is observed. No such discrimination was revealed from the compression isotherms. The latter indicate that squeezing the penetrant out of the monolayer upon compression does not allow for establishing the penetration equilibrium, so the monolayer remains supersaturated with the penetrant and shows an under-equilibrium orientation within the entire compression range, practically.