Your Independent Sequencing Guide
Emerging Technologies > Stratos Genomics
Stratos Genomics is building a nanopore-based single molecule sequencer. However, rather than directly sequencing the native DNA molecule, they have developed a process they call ‘sequencing-by-expansion’. They convert the DNA into an expanded molecule, or ‘xpandomer’, through a process similar to replication via polymerase. However, rather than incorporating a single base at a time into the newly formed strand, Stratos uses a modified polymerase which is able to incorporate strings of four complementary bases at a time. These 4-base oligos, called ‘Xprobes’, have four reporter molecules attached between the 2nd and 3rd base. The reporter molecules, which loop to the outside of the Xprobe so as to maintain the normal steric properties of a 4-mer oligo, are color-coded to represent one of the four bases of the original DNA molecule.
After the xpandomer has been synthesized, it is melted off the template strand, expanding to 50-times the size of the original target DNA molecule. It is then threaded through a solid state nanopore which reads off the sequence as represented by the reporter molecules, a process made easier by their high signal/noise ratio.While Stratos Genomics claims that this process can be scaled up to generate 10 million bases per second, they haven’t yet stated the targeted specifications their system will have at launch.
Key Paper: Kokoris, M.S. and McRuer,R.N. (2008) High throughput nucleic acid sequencing by expansion. US Patent 7,939,259
Status: early development
Projected Commercial Availability: unknown
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