Abstract
Ribonucleic acids (RNAs) are one of the most important types of biopolymers. RNAs play key roles in the storage and multiplication of genetic information. They are important in catalysis and RNA splicing and are the most important steps of translation. This chapter describes experimental methods for probing RNA structure and theoretical methods allowing the prediction of thermodynamically favorable RNA folding. These methods are complementary and together they provide a powerful approach to determine the structure of RNAs. The three-dimensional (tertiary) structure of RNA is formed by hydrogen-bonding among functional groups of nucleosides in different regions of the molecule, by coordination of polyvalent cations, and by stacking between the double-stranded regions present in the RNA. The tertiary structures of only some small RNAs have been determined by high-resolution X-ray crystallographic analysis and nuclear magnetic resonance analysis. The most widely used approach for the investigation of RNA structure is chemical and enzymatic probing, in combination with theoretical methods and phylogenetic studies allowing the prediction of variants of RNA folding. Investigations of RNA structures with different enzymatic and chemical probes can provide detailed data allowing the identification of double-stranded regions of the molecules and nucleotides involved in tertiary interactions.