Theoretical Biology and Biophysics Group, Theoretical Division Los Alamos, NM 87545, USA.|Theoretical Biology and Biophysics Group, Theoretical Division Los Alamos, NM 87545, USA.|Theoretical Biology and Biophysics Group, Theoretical Division Los Alamos, NM 87545, USA.|Theoretical Biology and Biophysics Group, Theoretical Division Los Alamos, NM 87545, USA.