Complementary base-pairing properties of cyclized and linear oligonucleotides.

Oligouridylates of varying chain lengths were synthesized by polynucleotide phosphorylase and cyclized by RNA ligase. Over chain lengths from 7 to 15, the bindings of the cyclized and linear oligomers to polyadenylate were measured on the basis of differential migration of bound and free oligomers on a gel exclusion column. Binding of the cyclized oligomers was found to be far weaker than that of their linear counterparts of equal length. Such a general reduction in base-pairing capacity due to the cyclized conformation, by limiting the strength of unintended base-pairing without obstructing the possible development of strong specific base-pairing, may represent an advantage important to the function and evolution of loop structures in tRNA and other RNA molecules.