Base composition-independent hybridization in tetramethylammonium chloride: a method for oligonucleotide screening of highly complex gene libraries.

An oligonucleotide hybridization procedure has been developed that eliminates the preferential melting of A X T versus G X C base pairs, allowing the stringency of the hybridization to be controlled as a function of probe length only. This technique, which uses tetramethylammonium chloride, is especially helpful whenever a highly complex library is screened with a pool of oligonucleotide probes, which usually vary widely in base composition. The procedure can also be applied advantageously whenever an exact match to an oligonucleotide probe is desired, such as in screening for clones having as little as a single-base alteration generated by in vitro mutagenesis.