ANALYSIS OF RNA BACKBONE By Eli Hershkovitz Guillermo Sapiro

Local conformation is an important determinant of RNA catal ysis and binding. The analysis of RNA conformation is particularly difficult due to the large numb er of degrees of freedom (torsion angles) per residue. Proteins, by comparison, have many few degrees of f reedom per residue. In this work we use and extend classical tools from statistics and signal proce ssing to search for clusters in RNA conformational space. Results are reported both for scalar analysis , where each torsion angle is separately studied, and for vectorial analysis, where several angles are simult aneously clustered. Adapting techniques from optimal quantization to the RNA structure, we find torsion an gle clusters and RNA conformational motifs. We validate the technique using well known conformati onal motifs and show how the simultaneous study of the total torsion angle space leads to the discovery of new motifs. The proposed technique is fully automatic and based on well-defined optimality criter ia.