Site specificity and geometry of H2O interactions with the conjugated pi systems of DNA bases

CHED 214

Tori O'Bannon, toribo@gmail.com, Department of Chemistry, University of Central Arkansas, 205 Laney, 201 Donaghey Ave, Conway, AR 72035
This study investigates water interactions with the aromatic rings of DNA bases, called water-pi interactions. Due to water's high dipole moment, we suspected that the partial positive charge of the H atoms interact with the DNA pi systems. The Protein Data Bank was screened for DNA structures with a resolution of 1.6 Å or higher and free of chemical modifications and bound ligands. We used Visual Basic programs to determine the distance and angle between each water molecule and the centroid of every DNA base. Waters with an angle less than 55° and a distance less than 5.0 Å from a centroid were found in all structures analyzed. These interactions were analyzed for sequence specificity and major/minor groove patterns. We concluded that water-pi interactions are common in DNA, sequence dependent, and potentially unstack DNA bases, contributing to the DNA distortion important in many cellular processes such as transcription regulation.