Theoretical insights into the nature of intermolecular interactions in cytosine dimer

In this study we discuss stacking interactions in cytosine dimer in conformations appearing in B-DNA crystals. The variational–perturbational scheme was applied for decomposition of the intermolecular interaction energy at the MP2 level of theory. The significant influence of the mutual orientation of cytosine monomers was observed not only on the total intermolecular interaction energy but also on its components: Different components of intermolecular interaction energy depend in different manner on parameters describing mutual orientation of cytosine monomers.