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    On 23/02/2012 10:27 PM, Jose Borreguero wrote:
    <blockquote
cite="mid:CAEee4gUXve=hGwMBy8GqkogqNxXr+si5GBsw8TN-Ff+hm941UA@mail.gmail.com"
      type="cite"><font color="#000099">I am not referring to any drift
        of the whole system, but to the diffusion of the lipid bilayer
        only. Diffusion of molecules in water is to be expected given
        sufficient time. I wonder what is a reasonable restraint to keep
        the center of mass of the membrane at Z=0.0<br>
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    <br>
    You can't have the bilayer drift unless the water drifts with it or
    through it. The former is more likely, thus you likely have COM
    motion.<br>
    <br>
    Mark<br>
    <br>
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cite="mid:CAEee4gUXve=hGwMBy8GqkogqNxXr+si5GBsw8TN-Ff+hm941UA@mail.gmail.com"
      type="cite"><font color="#000099">
        <br>
      </font><span style="color:rgb(0,0,153)">-Jose</span><br>
      <br>
      <div class="gmail_quote">On Wed, Feb 22, 2012 at 9:04 PM, Mark
        Abraham <span dir="ltr">&lt;<a moz-do-not-send="true"
            href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>&gt;</span>
        wrote:<br>
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              <div class="h5"> On 23/02/2012 10:26 AM, Jose Borreguero
                wrote:
                <blockquote type="cite">
                  <div class="gmail_quote"><font color="#000099">Dear
                      GROMACS users,<br>
                      <br>
                      While simulating a DLPC membrane, I noticed that
                      it tends to diffuse along the normal (Z-axis)
                      component. Is there a 'standard' restrain that is
                      used to prevent such diffusion?<br>
                      The first option I thought was to restrain the&nbsp;
                      center of mass of the whole membrane along the
                      Z-axis, but I don't know what is a reasonable
                      value for the force constant.<br>
                      If anyone has any experience dealing with this
                      kind of problem, please do reply.</font><br>
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            <font color="#000099"><br>
              Diffusion of the center of mass of the whole system is
              something that can be removed by an existing mechanism.
              See manual 7.3.3<span class="HOEnZb"><font color="#888888"><br>
                  <br>
                  Mark<br>
                </font></span></font> </div>
          <br>
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