Abstract
The need for computational characterization of DNA structure in the context of DNA bending/binding, B ->A transitions in protein-DNA complexes and also in the context of strand orientation especially in DNA triplexes and quadruplexes have given rise to several fine grained parameters, such as backbone conformations, sugar pucker and chi angle, local strand orientation, base pair and base pair step parameters backbone base inclination etc. With their unpaired bases, extensive non helical regions, non-canonical base pairs and tertiary interactions, RNA molecules host a large variety of recurrent structural and functional motifs and parameters such as Zp, defined in the context of double helical DNA base pairs and base pair steps and effectively used for A and B DNA differentiations, can not be used for computationally driven automated mining of complex RNA motifs. Though several algorithms have been proposed based on backbone conformational parameters and though algorithms for computational detection of base pairs and analysis of base pair parameters, are available, there are no reports of motif mining studies involving parameters which, as with Zp, simultaneously involve backbone conformation as well as base pairing geometry. In this work, we propose a novel set of parameters, Omega Pseudo-Torsions and Omega Distances, which capture backbone geometries at base(i) - base(j) interaction points and which can be used to computationally characterize structural features both in RNA and DNA. Pseudo torsion angles: Omega eta: P(i)-C4'(j)-P(j); Omega theta: P(i+1)-C4'(j)-P(j+1) Omega 1: P(i)-C4'(i)-C4'(j)-P(j+1); Omega 2: P(i+1)-C4'(i)-C4'(j)-P(j) Pseudo bond distance: Omega distance: C4'(i)-C4'(j) Where 'i' and 'j' are bases interacting through hydrogen bonds. We report the results of our benchmarking studies of Omega parameters with standard DNA structure classification parameters and of our preliminary studies on their effectiveness in classifying local geometries of RNA strands in different base pairing (canonical and non-canonical) contexts.