CIRCULARIZATION OF OLIGONUCLEOTIDES BY DISULFIDE BRIDGE FORMATION

An effective, convenient method for the circularization of oligonucleo tides has been developed, This procedure involved preparation of an ol igonucleotide with backbone-linked 5'- and 3'-terminal hexamethyleneth iol groups, followed by oxidation of the thiol groups with air or oxyg en to produce the corresponding circular sequence bridged via a bis(he xamethylene)disulfide moiety, The method has been applied to the circu larization of oligodeoxynucleotide sequences of varying lengths (5, 10 , 15, 20, 30 and 40 bases), and the circularization process was highly efficient as shown by HPLC or gel electrophoresis of the crude reacti on mixtures, Competing reactions such as dimerization were not signifi cant except for the longer sequences (30 and 40 bases), The circulariz ation of an eight base RNA sequence was also accomplished, as well as hexa-ethylene glycol bridged poly-T sequences capable of tripler forma tion.