Patent ID: 8575071

Claim:
A method of preparing a library of nucleic acid sequences comprising: (a) contacting first adapter oligonucleotides with a sample comprising target nucleic acid sequences under conditions to form first ligation products; (b) after step (a), contacting the sample with one or more hairpin oligonucleotides having a 5′ overhang portion configured to bind unligated first adaptor oligonucleotides whereby said 5′ overhang portion is complementary to and anneals to at least a portion of said unligated first adapter oligonucleotides; wherein the hairpin oligonucleotides do not anneal to the first ligation products; (c) after step (b), contacting the sample with second adapter oligonucleotides under conditions to bind to the first ligation products and form second ligation products, wherein the second ligation products form the library of nucleic acid sequences; and wherein the first and second adapters are linear and single-stranded.