Protein and nucleic acid complexes play a major role in variety of biological processes like enzymatic activity (ribozymes), protein assembly (virus capsids), transcription regulation etc. My work involves building computational models to study folding and assembly of large Protein-RNA/DNA complexes. Increase in system size limits the sampling using Molecular Dynamics (MD) simulations over a given run time. This makes it difficult to use MD for larger systems. I address this problem by using Coarse-grain (CG) models, in which multiple atoms are grouped together (based on some criteria) as a single “bead”. Each molecule is then represented using multiple beads and interactions between these beads are modeled to reliably reproduce experimental observations. I use these models to study dynamics and assembly of simple ssRNA icosahedral viruses.