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Interaction between lipids and antimicrobial oligomers studied by solid-state NMR.

ABSTRACT: Antimicrobial peptides and their synthetic analogues are well known to interact with the cell membrane, which has complex distributions of lipids. The phase behavior of DOPE/DOPG mixed lipids and the interaction between the lipids and several synthetic amphiphilic antimicrobial oligomers (AMOs) were studied by solid-state nuclear magnetic resonance (NMR). A phase diagram of the lipids over a broad window of water content was constructed. There are large areas in the phase diagram where multiple phases coexist, and the fraction of each phase at a given state is dependent on the sample's preparation and thermal history. The comparable stability of the different phases implies that even slight changes in the lipid condition could result in substantial changes to the phase structure, which may be utilized by living organisms to achieve many membrane functions. Nuclear Overhauser spectroscopy (NOESY) and several other NMR experiments indicated that the AMO primarily resides in the head group region of the lipids and that DOPE, the negative intrinsic curvature lipid, does not selectively enrich in the inverted hexagonal phase.

SUBMITTER: Hu W

PROVIDER: S-EPMC3810013 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Interaction between lipids and antimicrobial oligomers studied by solid-state NMR.

Hu Weiguo W Som Abhigyan A Tew Gregory N GN

The journal of physical chemistry. B 20110609 26

Antimicrobial peptides and their synthetic analogues are well known to interact with the cell membrane, which has complex distributions of lipids. The phase behavior of DOPE/DOPG mixed lipids and the interaction between the lipids and several synthetic amphiphilic antimicrobial oligomers (AMOs) were studied by solid-state nuclear magnetic resonance (NMR). A phase diagram of the lipids over a broad window of water content was constructed. There are large areas in the phase diagram where multiple ...[more]

PMID: 21612287

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Project description:Human posttranslationally modified N-ras oncogenes are known to be implicated in numerous human cancers. Here, we applied a combination of experimental and computational techniques to determine structural and dynamical details of the lipid chain modifications of an N-ras heptapeptide in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes. Experimentally, 2H NMR spectroscopy was used to study oriented membranes that incorporated ras heptapeptides with two covalently attached perdeuterated hexadecyl chains. Atomistic molecular dynamics simulations of the same system were carried out over 100 ns including 60 DMPC and 4 ras molecules. Several structural and dynamical experimental parameters could be directly compared to the simulation. Experimental and simulated 2H NMR order parameters for the methylene groups of the ras lipid chains exhibited a systematic difference attributable to the absence of collective motions in the simulation and to geometrical effects. In contrast, experimental 2H NMR spin-lattice relaxation rates for Zeeman order were well reproduced in the simulation. The lack of slower collective motions in the simulation did not appreciably influence the relaxation rates at a Larmor frequency of 115.1 MHz. The experimental angular dependence of the 2H NMR relaxation rates with respect to the external magnetic field was also relatively well simulated. These relaxation rates showed a weak angular dependence, suggesting that the lipid modifications of ras are very flexible and highly mobile in agreement with the low order parameters. To quantify these results, the angular dependence of the 2H relaxation rates was calculated by an analytical model considering both molecular and collective motions. Peptide dynamics in the membrane could be modeled by an anisotropic diffusion tensor with principal values of Dparallel=2.1x10(9) s(-1) and Dperpendicular=4.5x10(5) s(-1). A viscoelastic fitting parameter describing the membrane elasticity, viscosity, and temperature was found to be relatively similar for the ras peptide and the DMPC host matrix. Large motional amplitudes and relatively short correlation times facilitate mixing and dispersal with the lipid bilayer matrix, with implications for the role of the full-length ras protein in signal transduction and oncogenesis.

Dataset Information

Interaction between lipids and antimicrobial oligomers studied by solid-state NMR.

Publications

Interaction between lipids and antimicrobial oligomers studied by solid-state NMR.

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