Duplex formation of complementary oligoribonucleotides corresponding to the dihydrouridine loop neck region of several transfer ribonucleic acids.

Formation of short, double-stranded RNA helices by the complementary oligoribonucleotides GpApGpC, GpCpUpC, and ApGpCpUpC was established by the temperature-dependent changes in uv hypochromicity and circular dichroism spectra. These studies provide additional thermodynamic data on duplex formation. Duplexes (formula: see text) are especially significant as they: (1) correspond to a natural sequence, the dihydrouridine loop neck region, common to several tRNA molecules; (2) correspond to a proposed, partial recognition site for yeast phenylalanyl-tRNA ligase (EC 6.1.1.20); and (3) represent the first demonstration of a duplex with four base pairs, one of which is an A--U pair. These duplexes should serve as models for studies on tRNA-ligase interaction.