A model for gramicidin A?-phospholipid interactions in bilayers

Abstract

A model is proposed for the effect of gramicidin A' on the order and structure of phospholipid dispersions. According to this model, the addition of gramicidin A' influences the surrounding lipids via two independent mechanisms. The first arises from a drop in surface pressure for those lipids substantially bounded by gramicidin A'. The second mechanism arises from the increase in the phospholipid headgroup spacing due to the small polar region of the polypeptide. The model provides an explanation for the currently available NMR, X-ray diffraction and Langmuir monolayer results. The model also suggests mechanisms for the ability of gramicidin A' to trigger a transition of the lipid from the lamellar to hexagonal II phase, the dependence of this transition on the lipid chain length and the formation of a lamellar phase with lysophosphatidylcholine.

Physicochemical Characterization and Stability of Rifampicin Liposome Dry Powder Formulations for Inhalation

“…The addition of RIF molecules to the formulation without or with low CH content appeared to disorder the bilayer hydrocarbon chains, but this does not affect the head groups as reflected by the 31 P CSA. These opposite effects for the 2 H and 31 P data suggest that the RIF resides below the bilayer interface, having little effect on the head groups, but disordering the lipid chains 28, 29. This indicates that the incorporation of RIF in liposome membranes without or with low CH content may disorder the methylene chain, resulting in increased fluidity of the membrane and may cause vesicle leakage or fusion.…”

Exploring the structural relationship between encapsulated antimicrobial peptides and the bilayer membrane mimetic lipidic cubic phase: studies with gramicidin A′

“…Similar behaviour was observed for gA 0 . 44 Gramicidin A 0 and similar peptides are proposed to promote H II formation by increasing the volume of the hydrocarbon region, 31,45 and then occupying the positions in the H II phase in which the monolayer thickness is smallest. 40 In the absence of peptide, the H II phase is generally not observed until much higher temperatures, e.g.…”

The interaction of amyloid Aβ(1–40) with lipid bilayers and ganglioside as studied by 31P solid-state NMR

“…Several peptides including gramicidin, alamethicin, α-helical peptide and antimicrobial peptide also were shown to perturb bilayer structure to form non-lamellar hexagonal H II lipids by peptide-induced changes in lipid phases (Cornell et al, 1988;Gasset et al, 1988; Keller et al, 1996; Killian et al, 1985), in addition to the effect of lipid molecules themselves as mentioned above. The hydrophobicity and conformational flexibility of transmembrane peptides in lipid bilayers can affect their propensity to induce the formation of inverted non-lamellar phases by mechanisms not primarily dependent on lipid-peptide hydrophobic mismatch (Liu et al, 10 2001), although we note that a theoretical interpretation of a mechanism of the lamellarto-inverted hexagonal phase transition was also proposed, in relation to the membrane fusion process (Siegel, 1986;Siegel et al, 1997).…”