Issue 33, 2013

DNA hosted and aligned in aqueous interstitia of a lamellar liquid crystal – a membrane–biomacromolecule interaction model system

Abstract

We report that DNA molecules can be intercalated and macroscopically oriented in the aqueous interstitia of a lyotropic lamellar liquid crystal. Using UV-vis linear dichroism and fluorescence spectroscopy we show that double-stranded oligonucleotides (25 base pairs) in the water–octanoate–decanol system remain base-paired in the B conformation and are confined in two dimensions, with the helix axis preferentially parallel to the lipid bilayer surfaces but free to rotate within this plane. The degree of helix confinement and the corresponding 2-D orientation can be improved by decreasing the thickness of the water interstitia via the fraction of water in the ternary mixture. Not surprisingly, the corresponding single-stranded oligonucleotides are not aligned, with their persistence length being short in comparison to the lamellar interstitium thickness. We propose this as a model system for studying interactions of DNA–ligand complexes near a lipid bilayer membrane which we demonstrate by using dye probes that are either covalently attached to one end of the oligonucleotide or reversibly bound by intercalation between the base pairs. Three cationic dyes, all strongly bound by intercalation to DNA when free in solution, are found to not bind to DNA but to prefer the membrane surface. The covalently attached Cy5 also binds to the bilayer while Cy3 tends to end-stack to the oligonucleotide duplex. The orientation of Cy5 parallel to the membrane indicates that electrostatic surface binding predominates over insertion into the hydrophobic interior of the membrane. Anionic and zwitterionic dyes (FAM and ROX) are found to remain randomly oriented in the water between the lipid bilayer surfaces.

Graphical abstract: DNA hosted and aligned in aqueous interstitia of a lamellar liquid crystal – a membrane–biomacromolecule interaction model system

Supplementary files

Article information

Article type
Paper
Submitted
10 Apr 2013
Accepted
25 Jun 2013
First published
27 Jun 2013

Soft Matter, 2013,9, 7951-7959

DNA hosted and aligned in aqueous interstitia of a lamellar liquid crystal – a membrane–biomacromolecule interaction model system

N. Carlsson, F. Jonsson, L. M. Wilhelmsson, B. Nordén and B. Åkerman, Soft Matter, 2013, 9, 7951 DOI: 10.1039/C3SM50982F

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