"The primary advantages of our system are the simplicity of its design combined with the ease with which the fluorescence brightness and color can be tuned," Armitage said.
To achieve greater brightness, the Carnegie Mellon team assembled well-defined nanostructured DNA templates that bind multiple fluorescent dye molecules between base pairs in the DNA helix (see image). This arrangement keeps dyes far enough away from each other to avoid canceling out each others fluorescence. The DNA templates can also be modified to bind to other molecules or to the surface of a cell of interest. The innovative design creates nanotags with large light-harvesting capabilities and very high light-emission (fluorescence) intensities. Because the DNA can accommodate one dye for every two base pairs, a DNA nanostructure with 30 base pairs can bind up to 15 fluorescent dye molecules. The resulting dye-DNA complexes are approximately 15 times brighter than an individual dye molecule. And they can be made even brighter by simply increasing the number of base pairs in the DNA nanostructure.
Multicolor experiments are possible because the DNA nanotags contain "light-harvesting" dyes within the DNA helix that are excited by one wavelength of light and then transfer that excitation energy to "light-emitting" dyes on the nanotags surface. The light-emitting dyes can fluoresce at a different color from the light-harvesting dye. For example, one type of DNA nanotag can act as an antenna that efficiently harvests blue light and transfers that light energy to another dye within the nanostructure. The second dye then emits orange, red
Contact: Lauren Ward
Carnegie Mellon University