Imaging Platform Improves Limited Resolution Abilities of Single-Molecule Microscopes

A new highly versatile and inexpensive microscope imaging platform has been developed that is designed to visualize objects with molecular-scale resolution and unprecedented complexity.

DNA-PAINT and Exchange-PAINT technologies (right) dramatically improve the limited resolution abilities of single-molecule microscopes (left). Shown are structures of thin microtubule fibers (green) that build a skeleton within cells and mitochondria (magenta) as the cell’s biochemical powerhouses both turned from blurry into super-sharp molecular images. Courtesy of Wyss Institute at Harvard University.

Scientists from Wyss Institute at Harvard University have developed the DNA-powered imaging technology that can reveal the inner workings of cells at the single molecule level, using conventional microscopes found in most laboratories. The key to the technology is the interaction of two short strands of DNA, one called the “docking strand” that is attached to the molecular target to be visualized and the other, called the “imager strand,” which carries a light-emitting dye.

Despite the recent revolution of optical imaging technologies that has enabled the distinction of molecular targets residing less than 200 nanometers apart from each other, modern superresolution techniques have still been unable to accurately and precisely count the number of biomolecules at cellular locations.

DNA-PAINT — a variation of point accumulation for imaging in nanoscale topography — uses the transient binding of short fluorescently labeled oligonucleotides for simple and easy-to-implement multiplexed super-resolution imaging. It achieves sub-10-nm spatial resolution in vitro on synthetic DNA structures.

A multiplexing approach known as Exchange-PAINT allows sequential imaging of multiple targets using only a single dye and a single laser source. Through this process, the scientists demonstrated ten-color super-resolution imaging in vitro on synthetic DNA structures as well as four-color two-dimensional imaging and three-color 3D imaging of proteins in fixed cells.

With DNA-PAINT superresolution microscopy and qPAINT analysis, researchers will be able to quantify the number of molecules at specific locations in the cell without the need to spatially resolve them and without an expensive large super-resolution microscope.

The study was published in the journal Nature (doi:10.1038/nmeth.2835).