SURFACE-PROMOTED REPLICATION AND EXPONENTIAL AMPLIFICATION OF DNA ANALOGS

Self-replicating chemical systems have been designed and studied to id entify the minimal requirements for molecular replication(1), to trans late the principle into synthetic supramolecular systems(2) and to der ive a better understanding of the scope and limitations of self-organi zation processes(3) that are believed to be relevant to the origin of life on Earth(4). Current implementations make use of oligonucleotide analogues(5-12), peptides(13-17), and other molecules(18-24) as templa tes and are based either on autocatalytic, cross-catalytic, or collect ively catalytic pathways for template formation. A common problem of t hese systems is product inhibition, leading to parabolic instead of ex ponential amplification(25). The fatter is the dynamic prerequisite fo r selection in the darwinian sense(26,27). We here describe an iterati ve, stepwise procedure for chemical replication which permits an expon ential increase in the concentration of oligonucleotide analogues. The procedure employs the surface of a solid support and is called SPREAD (surface-promoted replication and exponential amplification of DNA an alogues). Copies are synthesized from precursor fragments by chemical ligation on immobilized templates, and then Liberated and immobilized to become new templates. The process is repeated iteratively. The role of the support is to separate complementary templates which would for m stable duplexes in solution. SPREAD combines the advantages of solid -phase chemistry with chemical replication, and can be further develop ed for the non-enzymatic and enzymatic amplification of RNA, peptides and other templates as well as for studies of in vitro evolution and c ompetition in artificial chemical systems. Similar processes may also have played a role in the origin of life on Earth, because the earlies t replication systems may have proliferated by spreading on mineral su rfaces(28-33).