Modified oligonucleotides as alternatives to the synthesis of mixed probes for the screening of cDNA libraries

Two simple alternatives to the synthesis of mixed oligodeoxyribonucleotide probes are described: mixed deblocking of triazolodeoxynucleosides for the A/G and C/T degeneracies or incorporation of 2-amino-2'-deoxyadenosines into a determined sequence for a higher stability of the hybridization duplexes. The synthetic oligodeoxyribonucleotides obtained were successfully tested in comparison with a classical mixed probe for their capacity to identify specific cDNA clones of human antithrombin III. The results are discussed with respect to the utilization of these synthetic oligonucleotides as hybridization probes for the isolation of cloned cDNA sequences.