US Patent 8431691 Reagents, methods, and libraries for bead-based sequencing

The present invention provides methods for determining a nucleic acid sequence by performing successive cycles of duplex extension along a single stranded template. The cycles comprise steps of extension, ligation, and, preferably, cleavage. In certain embodiments the methods make use of extension probes containing phosphorothiolate linkages and employ agents appropriate to cleave such linkages. The invention provides methods of determining information about a sequence using at least two distinguishably labeled probe families. In certain embodiments the methods acquire less than 2 bits of information from each of a plurality of nucleotides in the template in each cycle. In certain embodiments the sequencing reactions are performed on templates attached to immobilized beads. The invention further provides sets of labeled probes containing phosphorothiolate linkages. In addition, the invention includes performing multiple sequencing reactions on a single template by removing initializing oligonucleotides and extended strands and performing subsequent reactions using different initializing oligonucleotides.