Method for selecting functional deoxyribonucleotide derivatives

An improvement in a method for creating a catalyst for a preselected reaction, said method comprising:

• a) synthesizing a mixture of oligonucleotides from nucleotide building blocks each of the oligonucleotides having a region of randomized sequence
• b) incubating said mixture under conditions where oligonucleotides that catalyze said reaction undergo as a result of their catalytic activity a chemical transformation that makes them preferentially partitionable from or amplifiable in preference to oligonucleotides in the remainder of the mixture that have diminished or none of said catalytic activity,
• c) partitioning the oligonucleotides with increased catalytic activity from the other oligonucleotides in the mixture,
• d) amplifying the oligonucleotides having increased catalytic activity in vitro to yield a mixture of oligonucleotides enriched in those with increased catalytic activity,
• wherein the improvement comprises including among said nucleotide building blocks those carrying nucleobases selected from the group consisting of ##STR3## wherein -R designates the point of attachment, X is either a nitrogen atom or a carbon atom bearing a substituent Z, Z is either a hydrogen, an unfunctionalized lower alkyl, alkynyl, or alkyl-alkynyl chain, or a lower alkyl, alkenyl, alkynyl, alkenyl-alkyl or alkyl-alkynyl chain bearing an amino, carboxyl, hydroxy, thiol, aryl, indole, or imidazoyl group, Y is either N or CH, Q is a lower alkyl, alkenyl, alkynyl, alkenyl-alkyl or alkyl-alkynyl chain bearing an amino, carboxyl, hydroxy, thiol, aryl, indole, or imidazoyl group, and the ring contains no more than three nitrogens consecutively bonded.