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<title>MCCCS Towhee (SPC-E water)</title>
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<div align="center"> <font size="5"> <b><font face="Arial, Helvetica, sans-serif"><a name="top"></a>MCCCS
Towhee (SPC-E water)</font></b> </font> </div>
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<p> </p>
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<td width="697" valign="top"> <b>Overview</b>
<ul>
This section covers the Simple Point Charge - Extended (SPC-E) water model parameters as they are implemented into
the towhee_ff_SPC-E file in the ForceFields directory. All of the Towhee atom types for the SPC-E water force
field are listed, along with a short description of their meanings. This is
not really a comphrehensive stand-alone force field, but instead a popular model for water.
Note that these are Lennard-Jones (12-6)
parameters and can only be combined with other Lennard-Jones (12-6) force fields.
Any discrepencies (especially typos) from the published SPC-E force field values
are the sole responsibility of Marcus G. Martin, and I welcome feedback on how this implementation compares
with other programs.
<p> </p>
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<b>References for SPC-E water</b>
<ul>
<li><a href="../references.html#berendsen_et_al_1987">Berendsen <i>et al.</i> 1987</a></li>
</ul>
<b>SPC-E in Towhee</b>
<ul>
The official force field name for Simple Point Charge - Extended water in Towhee is 'SPC-E'. Here I list all of
the SPC-E atom names for use in the towhee_input file, along with a brief description (although
the meaning of the atom names should be obvious).
Please note that the capitalization and spacing pattern is important
and must be followed exactly as listed here.
<ul>
<li><b>'HW'</b> : hydrogen in water</li>
<li><b>'OW'</b> : oxygen in water</li>
</ul>
</ul>
<b>Coulombic interactions</b>
<ul>
Atom centered point charges are used to represent the electrostatic interactions.
<ul>
<li><b>'HW'</b> : 0.4238</li>
<li><b>'OW'</b> : -0.8476</li>
</ul>
</ul>
<b>Improper torsions</b>
<ul>
This force field only has parameters for water so there are no improper torsions.
</ul>
<b>Proteins</b>
<ul>
This force field only has parameters for water, and while you are welcome to use them with another protein
force field, there are no amino acids in the SPC-E force field.
</ul>
<a href="../towhee_capabilities.html">Return to the Towhee Capabilities web page</a>
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<i><font size="2">Send comments to:</font></i> <font size="2">
<a href="mailto:marcus_martin@users.sourceforge.net">Marcus G. Martin</a><br>
<i>Last updated:</i>
<!-- #BeginDate format:Am1 -->September 07, 2005<!-- #EndDate -->
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