Local and translational dynamics in DNA-lipid assemblies monitored by solid-state and diffusion NMR
2008 (English)In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1778, no 1, 214-228 p.Article in journal (Refereed) Published
The influence of electrostatic interactions on the dynamic properties of complexes containing DNA and mixtures of cationic- (DDA) and zwitterionic (DLPC) lipids are studied by means of NMR. The systems are arranged in lamellar membrane stacks intercalated by DNA molecules. This is confirmed by P-31-NMR, where a superposition of an axially symmetric powder pattern arising from the phospholipid membrane and an asymmetric tensor due to DNA can be fitted to the experimentally observed lineshape. The local mobility and order is assessed using two solid-state NMR techniques applicable to samples with natural isotopic abundance: WIdeline SEparation (WISE) and Separated Local Field (SLF) spectroscopy. Both experiments yield highly resolved C-13 spectra in the direct dimension. The indirect dimension contains information about molecular dynamics through the H-1 dipolar linewidth (WISE) or the H-1-C-13 dipolar coupling constant (SLF). The experiments suggest that DNA is static while it induces an increased disorder in the hydrocarbon chains as compared to the parent lipid case. DDA chain order is more affected than DLPC due to the attractive electrostatic interaction between DNA and the cationic lipid. Translational dynamics of the lipids and the water was measured with the Pulsed Field Gradient STimulated Echo (PFG STE) technique. The influence of lamellar domain size and the angular dependence of the diffusion coefficients and nuclear relaxation times on the results of the PFG STE experiments are discussed. The local water diffusion coefficient is reduced by a factor four from the value of bulk water, and increases as the DLPC content is increased. We observe two lipid components with an order of magnitude difference in diffusion coefficients in the DNA:DDA:DLPC precipitate and these are assigned to DLPC (fast) and DDA (slow). Cationic lipid (DDA) diffusion is decreasing a factor of 2 when DLPC is added to the pure DNA:DDA system, indicating DNA-induced lipid segregation within the bilayer and the transition from locally 2D to 1D diffusion of the DDA. The results show that DNA-lipid electrostatic interactions reduce the long-range lipid mobility but locally enhance the hydrocarbon chain dynamics by perturbing the preferred lipid packing.
Place, publisher, year, edition, pages
2008. Vol. 1778, no 1, 214-228 p.
DNA-lipid assemblies, membrane local mobility, membrane local order, lateral diffusion, domain size, domain formation, solid-state NMR, diffusion NMR
IdentifiersURN: urn:nbn:se:su:diva-59151DOI: 10.1016/j.bbamem.2007.09.035ISI: 000253269500023OAI: oai:DiVA.org:su-59151DiVA: diva2:425541
authorCount :42011-06-212011-06-212011-06-21Bibliographically approved