ON THE ORIGIN OF THE LONG-RANGE ATTRACTION BETWEEN SURFACE-CONFINED DNA BASES

Surface forces apparatus measurements (Phys. Rev. Lett., 73 (1994) 278 0) have established strongly attractive long-range forces between thym ine- and adenine-terminated ester monolayers approaching in an aqueous environment. The origin of these forces has not yet been completely u nderstood. We report here a molecular modelling investigation of the f orces between single adenine and thymine DNA bases and a molecular dyn amics simulation of monolayers of the same amphiphilic esters. The tai l regions of the monolayers are in a fluid, disordered state. However, the thymidine- and adenosine-terminated head groups show a tendency t oward aggregation and domain formation. The simulation reveals that th e orientation of the water molecules is well expressed only at close d istances to the DNA bases. The hydrogen bonds between the nucleotides themselves, and with water, are explicitly considered in the performed simulations.