Jan Jensen edited subsection_Hydrogen_bond_scans_label__.tex  almost 9 years ago

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\subsection{Hydrogen bond scans} \label{subsec:HBscan}  Three systems with an N-methylacetamide and a hydrogen bond acceptor were the basis of the \HN hydrogen bond parameterization. The hydrogen bonding system for the negatively charged aspartic $\Delta \sigma_{HB}$  and glutamic acids side chains were modeled with an acetate anion. The system for bonding with $\Delta \sigma_{H\alpha B}$ (cf. Eq \ref{eqn:procs}) is parameterized using  thealcohol groups of threonine and serine was done with a methanol molecule. The system for bond with another backbone segment was modeled with an additional N-methylacetamide. The \HA scans used a methyl capped alanine peptide to  model the donor residue backbone systems shown in Figures \ref{fig:HB}  and the same three molecules to model the acceptors. See {\bf \ref{supinfo} Supplementary Information} \fref{fig:hbondscans}{\bf-\ref{fig:ALAscans}} for schematics of the model system used. \ref{fig:HAB}.  For \HN $\Delta \sigma_{HB}$  the scan was are  done by scanning over the hydrogen bond length $r_{OH}$, the bond angle $\theta$ $\theta_{\mathrm{H}}$  defined by H..O=C or H..O-C and the dihedral angle $\rho$ $\rho_{mathrm{H}}$  defined by H..O=C-N, H..O=C-C or H..O-C(..)H\textsuperscript{O}. H..O-C(..)H^{O}.  The bond length scan was scanned from $1.5$ \AA\xspace 1.5  to $4.0$ \AA\xspace 4.0 Å  in $0.125$ 0.125  Å steps. $\theta$ $\theta_{\mathrm{H}}$  was scanned from $180$ 180.0  to $90\deg$ 90.0$\deg$  in $10\deg$ 10.0 $\deg$  steps and $\rho$ $\rho_\mathrm{H}$  was done in the entire range $-180$ -180$\deg$  to $180$. 180$\deg$.  The \HA hydrogen bonding the scan was done equivalently. The bond length $r_{OH\alpha}$ was scanned from $1.8$ to $4.0$ \AA\xspace in steps of $0.2$ \AA. The bond angle $\theta$ defined by H\(\alpha\)..O=C or H\(\alpha\)..O-C was scanned from $180$ to $90^\circ$ with $10^\circ$ steps size. The $\rho$ dihedral H\(\alpha\)..O=C-N, H\(\alpha\)..O=C-C and H\(\alpha\)..O-C(..)H\textsuperscript{O} was scanned in steps of $15^\circ$ over the entire range.