Bright spots captured by a camera in a new technique called mbPAINT, developed at Rice University, helped researchers pinpoint the specific location of a short, known DNA sequence along a single strand of DNA.
Researchers at Rice University have demonstrated, in a proof-of-concept experiment, that their new super-localization microscopy technique may be able to identify DNA sequences as short as 50 nucleotides at room temperature. This is not something that can be accomplished by any currently available technology – standard microscopy cannot observe objects that small, while electron microscopy requires that the sample be cryogenically frozen, or be stored in a vacuum. The super-resolution technique, called ”motion blur point accumulation for imaging in nanoscale topography” (mbPAINT), which can image structures as small as 30 nanometers, is essentially a “movie” captured of fluorescent DNA probes which give off light when they pass over a specifically targeted sequence in an immobilized strand of DNA. In the experimental set-up, a fluorescent camera observes an immobilized strand of DNA, while DNA probes suspended in a moving liquid pass over it, unseen to the camera, until they bind with the targeted DNA segment for several milliseconds, and give off sufficient fluorescent light for the camera to capture its location, before being pulled away again.
The imaging set-up is brilliant in its design, and more specifically in the analysis of the image: due to physical limitations of light microscopy (the underlying principle of this set-up), no actual image of the DNA sequence, or DNA probes is available for capture – the wavelength of visible light is greater than the size of the image being captured. The captured image is of motion blur generated by the movement of the probes, with the occasional fluorescent spot appearing at the precise location of the DNA sequence in question. A superimposition of all the captured images shows collective motion blur, with a very precise fluorescent spot on the DNA sequence that is being analysed. According to Christy Landes, lead researcher of the project, the team would like to develop the technology further, capturing ever smaller fragments of DNA.
If this technology progresses, it may be able to locally pinpoint individual nucleotides responsible for various diseases or genetic disorders, which could be an incredible accomplishment for the world of medicine and genetic mapping.
Here’s a video of the imaging events and the rendered results: