Amplification by nucleic acid-templated reactions.

Nucleic acid-templated reactions enable the design of conditional reaction systems, in which bond formation occurs only when a particular DNA or RNA molecule is present. Such reaction systems are currently being explored for applications in DNA/RNA diagnosis, drug screening and as a means to design gene expression specific therapy. However, biological nucleic acid templates usually have low abundance. Therefore, either the targeted nucleic acid template has to be multiplied by means of an amplification step or the template itself has to act as a catalyst which amplifies product formation. This critical review highlights the recent advancements in nucleic acid-templated reactions that proceed with turnover in template and thereby provide a means of amplification. Improvements in reaction engineering and the development of new chemistries have pushed the limits from 10(1) to 10(2)-10(3) turnovers. This includes reaction systems that lead to the ligation of oligonucleotides or to the interconversion of appended functional groups beyond ligation as well as templated chemistries that enable the activation of catalysts for subsequent triggering of reactions between non-nucleotidic substrates. The present limitations and future opportunities are discussed.