a collection of powerful new techniques for oligonucleotide synthesis and for the use of modified oligonucleotides in biotechnology. among the protocol highlights are a novel two-step process that yields a high purity, less costly, dna, the synthesis of phosphorothioates using new sulfur transfer agents, the synthesis of lna, peptide conjugation methods to improve cellular delivery and cell-specific targeting, and triple helix formation. the applications include using molecular beacons to monitor the pcr amplification process, nuclease footprinting to study the sequence-selective binding of small molecules of dna, nucleic acid libraries, and the use of small interference rna (sirna) as an inhibitor of gene expression.