Reversible hybridization of DNA anchored to a lipid membrane via porphyrin.

The binding of zinc-porphyrin-anchored linear DNA to supported lipid membranes was studied using quartz crystal microbalance with dissipation monitoring (QCM-D). The hydrophobic anchor is positioned at the ninth base of 39-base-pair-long DNA sequences, ensuring that the DNA is positioned parallel to the membrane surface when bound, an important prerequisite for using this type of construct for the creation of two-dimensional (2D) DNA patterns on the surface. The anchor consists of a porphyrin group linked to the DNA via two or three phenylethynylene moieties. Double-stranded DNA where one of the strands was modified with either of these anchors displayed irreversible binding, although binding to the membrane was faster for the derivatives with the short anchor. The binding and subsequent hybridization of single-stranded constructs on the surface was demonstrated at 60 °C, for both anchors, revealing a coverage-dependent behavior. At low coverage, hybridization results in an increase in mass (as measured by QCM-D) by a factor of ~1.5, accompanied by a slight increase in the rigidity of the DNA layer. At high coverage, hybridization expels molecules from the membrane, associated with an initial increase, followed by a decrease in DNA mass (as detected both by QCM-D and by an optical technique). Melting of the DNA on the surface was performed, followed by rehybridization of the single-stranded species left on the surface with their complementary strand, demonstrating the reversibility inherent in using DNA for the formation of membrane-confined nanopatterns.