Insights in the Organization of DNA-Surfactant Monolayers Using Cryo-Electron Tomography

摘要

The organization and complexation of DNA has been a subject of intensive research, not only to gain insight into biological processes but also to understand its behavior in biomedical applications. In particular, the behavior of DNA in the presence of cationic surfactants is of interest to understand phenomena involved in gene transfection, DNA sensing, and more recently the layer-by-layer synthesis of DNA-based biomaterial coatings. In addition to the DNA—surfactant complexes studied in the bulk phase, Langmuir monolayers are frequently used to obtain information about DNA—surfactant interactions. The model for such a system generally involves nucleic acid molecules that are orderly bound via electrostatic interactions to a closely packed monolayer of cationic surfactants. Several techniques, such as Brewster angle microscopy (BAM), in situ grazing incidence X-ray diffraction, and infrared reflection absorption spectroscopy (IR-RAS), have been applied to obtain information about the organization of these monolayer systems; however, from these studies, no generalizing conclusions could be drawn. Whereas Mowald et al. concluded that DNA becomes aligned due to the compression of the complex, Okahata showed that the presence of an intercalating dye was required for the ordering of DNA under a surfactant monolayer. Significantly, Yamaoka et al. demonstrated that the complex present at the air—water interface changes its structure upon deposition to a solid substrate.