Our SMRT technology harnesses the natural process of DNA replication, which is a highly efficient and accurate process. The enzyme responsible for replicating DNA in nature is called the DNA polymerase. The DNA polymerase attaches itself to a strand of DNA to be replicated, examines the individual base at the point it is attached, and then determines which of four building blocks, or nucleotides, is required to replicate that individual base. After determining which nucleotide is required, the polymerase incorporates that nucleotide into the growing strand that is being produced. After incorporation, the enzyme advances to the next base to be replicated and the process is repeated. Our SMRT technology enables the observation of DNA synthesis as it occurs in real time. To overcome the challenges inherent in observing an enzyme that is 15 nanometers, or nm, in diameter running in real time, we developed three key innovations:
• The SMRT Cell
• Phospholinked nucleotides
• The PacBio RS
The SMRT Cell
One of the fundamental challenges with observing a DNA polymerase working in real time is the ability to detect the incorporation of a single nucleotide, taken from a large pool of potential nucleotides, during DNA synthesis. To resolve this problem, we applied the same principle that operates in the metallic screen of a microwave oven door. In a microwave oven, the screen is perforated with holes that are much smaller than the wavelength of the microwaves. Because of their relative size, the holes prevent the much longer microwaves from passing through and penetrating the glass. However, the much smaller wavelength visible light is able to pass through the holes in the screen, allowing food to be visible. We have reduced this same principle to the nanoscale and we call our innovation a zero-mode waveguide, or ZMW.
