The goal of the proposed research is to understand the relation between the structure and function of ribonucleic acids (RNAs). In order to achieve this goal, oligoribonucleotides of defined sequence will be synthesized with enzymes for use in three major types of experiments. First, the value of the association constant (K) of an oligomer to a complementary sequence on a RNA will be used as a measure of the local structure of the RNA. Changes in the Ks of oligomer probes to different functional forms of a RNA can be interpreted as corresponding changes in different parts in RNA structure. For example, a transfer RNA inactivated by the removal of a single nucleotide may show altered values of K for oligomers binding to a totally different region of the tRNA, indicating that the nucleotide was critical to the integrity of the tertiary structure of the RNA. Second, oligomers will be synthesized which have a similar structure as a portion of a RNA and assayed for activity with enzymes which interact with that RNA. With synthetic control over the RNA substrate, the structural requirements for the protein-nucleic acid interaction may be defined. For example, the synthesis of a tRNA anticodon loop is proposed for assay in trimer dependent ribosome binding assay. Third, the properties of different oligomer model helices as a function of temperature and solvent will aid understanding of the specificity and thermodynamics of nucleic acid interactions. Information obtained from the model compounds can be used to predict the conformation of RNA molecules to known sequence.