Analysing the morphology of DHPC/DMPC complexes by diffusion NMR
(English)Manuscript (preprint) (Other academic)
Mixtures of lipids and detergents are known to form bicelles at certain parameter ranges, but many un-certainties remain concerning the details of the phase be-haviour of these mixtures and the morphology of the formed lipid assemblies. Here we used NMR diffusion data in com-bination with the multivariate processing method SCORE to analyze mixtures of DHPC and DMPC with the relative concentration q=[DMPC]/[DHPC]=0.5 at total lipid con-centrations from 15 to 300 mM. With this approach we were able to resolve the heavily overlapping mixture spectra into component spectra and obtained reliable diffusion coeffi-cients for lipid concentrations in the range 15 to 200 mM. Between 200 and 300 mM, the similar diffusion coefficients in combination with substantial signal overlap makes it difficult to get very reliable spectra and diffusion coeffi-cients with standard processing parameters, but overfactoring provided useful diffusion coefficient estimates also at these concentrations. At 50–300 mM total lipid concentration, the radii estimated from the diffusion coeffi-cient of DMPC indicate assemblies of the appropriate bicelle size, although small size variations exist, while at lower concentrations the morphology appears to change to larger assemblies. Taken together, the results suggest that for q=0.5 DMPC/DHPC mixtures there is a relatively broad concentration range above 50 mM where bicelles may relia-bly be assumed to adopt the 'classical' bicelle morphology. At lower concentrations there is evidence for a more com-plex morphology with more than one type of lipid assembly in the sample.
Research subject Biophysics
IdentifiersURN: urn:nbn:se:su:diva-107826OAI: oai:DiVA.org:su-107826DiVA: diva2:750691