The non-bonded interactions were treated by a combination of LJ-ID and electrostatics potentials, with the electrostatics interactions being decomposed in short-and long-range contributions. The LJ-ID and the short-range Coulomb potentials were truncated at 1 and 0.8 nm, respectively. The long-range electrostatic interactions were evaluated with the particle-particle-particle-mesh (PPPM) method with a desired relative error in forces of 10 -4 kcal/(mol Å). All bonds and angles were constructed with harmonic potentials, and the OPLS style was considered for dihedrals. The SHAKE algorithm was employed for all hydrogen bond constraints.