By directly sequencing single molecules of DNA or RNA, Helicos' True Single Molecule Sequencing (tSMS™) and Direct RNA Sequencing (DRS™) technologies significantly increase the speed of sequencing, while also decreasing the cost.
tSMS and DRS enables the simultaneous sequencing of large numbers of strands of single DNA or RNA molecules by using a proprietary form of sequencing-by-synthesis in which labeled bases are sequentially added to the nucleic acid templates captured on a flow cell. Our optimized formulation ensures high accuracy of each base addition, which are detected by the HeliScope™ Single Molecule Sequencer to elucidate the sequence of bound strands.
Download the Helicos tSMS Technology Primer (pdf).
How tSMS Works
Within two flow cells, billions of single molecules of sample DNA are captured on an application-specific proprietary surface. These captured strands serve as templates for the sequencing-by-synthesis process:
Polymerase and one fluorescently labeled nucleotide (C, G, A or T) are added.
- The polymerase catalyzes the sequence-specific incorporation of fluorescent nucleotides into nascent complementary strands on all the templates.
- After a wash step, which removes all free nucleotides, the incorporated nucleotides are imaged and their positions recorded.
- The fluorescent group is removed in a highly efficient cleavage process, leaving behind the incorporated nucleotide.
- The process continues through each of the other three bases.
- Multiple four-base cycles result in complementary strands greater than 25 bases in length synthesized on billions of templates—providing a greater than 25-base read from each of those individual templates.
Raw tSMS Image
An image taken by the HeliScope Single Molecule Sequencer.
Inset shows a close-up view of individual single molecules.
