SELF-REPLICATION OF HEXADEOXYNUCLEOTIDE ANALOGS - AUTOCATALYSIS VERSUS CROSS-CATALYSIS

In the presence of a water-soluble carbodiimide, 5'-protected tri-deox ynucleotide 3'-phosphates and 3'-protected 5'-aminotrideoxynucleotides reacted to give hexadeoxynucleotides with a central 3'-5'-phosphorami date linkage. The trimer sequences were CCG and CGG and were used as b oth the 5'-amine and the 3'-phosphate derivatives. The kinetics of the reactions were monitored by HPLC and analyzed with the SimFit program . In the first set of experiments, the formation of a single hexamer w as studied in the absence of any hexadeoxynucleotide and in the presen ce of one of four hexadeoxynucleotides with the sequence of the reacti on products. Here, self-complementary hexamers were always found to be formed faster than non-self-complementary hexamers because of autocat alytic self-replication. In the second set of experiments, the simulta neous formation of all four reaction products allowed both autocatalys is and cross-catalysis to occur. In this case all hexamers were synthe sized with similar rates, In all experiments template effects were onl y observed for those sequences which were complementary to the reactio n product. Autocatalysis as well as cross-catalysis was always accompa nied by product inhibition leading to parabolic growth characteristics .