<br /><br /><span>On 25/05/11, <b class="name">郭漫 </b> <pysgm2010@hotmail.com> wrote:</span><blockquote cite="mid:BLU165-W546FA5D1C776E333BDE01CBC740@phx.gbl" class="iwcQuote" style="border-left: 1px solid rgb(0, 0, 255); padding-left: 13px; margin-left: 0pt;" type="cite"><div class="mimepart text html"><span><p>
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Hello users,<br />I<span id="result_box" lang="en"><span class="hps" title="点击可显示其他翻译"> followed the</span> <span class="hps" title="点击可显示其他翻译">tutorial</span> <span class="hps" title="点击可显示其他翻译">steps to do</span></span> umbrella sampling of GROMACS Tutorial, (<span class="short_text" id="result_box" lang="en"><span class="hps" title="点击可显示其他翻译">This is the</span> <span class="hps" title="点击可显示其他翻译">tutorial</span> <span class="hps" title="点击可显示其他翻译">site </span></span><a href="http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/gmx-tutorials/umbrella/index.html" target="1">http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/gmx-tutorials/umbrella/index.html</a>) and get the
PMF is close to -50 kcal/mol. However, when I put amber99sb parameter
instead of gromos96 53a6 parameter, <span id="result_box" lang="en"><span class="hps" title="点击可显示其他翻译">without changing the</span> <span class="hps" title="点击可显示其他翻译">other parameters and steps,</span></span>the result is about -35 kcal/mol. I
don't know why the<span id="result_box" lang="en"><span class="hps" title="点击可显示其他翻译"> difference</span></span> is so large between them, and i need your help for <span id="result_box" lang="en"><span class="hps" title="点击可显示其他翻译">explaining</span> <span class="hps" title="点击可显示其他翻译">what is the reason</span> <span class="hps" title="点击可显示其他翻译">for the difference</span><span title="点击可显示其他翻译">, simply</span> <span class="hps" title="点击可显示其他翻译">because I</span> <span class="hps" title="点击可显示其他翻译">changed</span> <span class="hps" title="点击可显示其他翻译">the </span><span class="hps" title="点击可显示其他翻译">force filed,</span> <span class="hps" title="点击可显示其他翻译">or some other</span> <span class="hps" title="点击可显示其他翻译">possible causes</span></span>.</p></td></tr></tbody></table></p></span></div></blockquote><br />If all you've changed is the force field, and these simulations are long enough to produce converged measurements, then "welcome to the jungle". Different force fields have been demonstrated to be good or bad on different types of systems for different types of properties. Choosing the right force field is normally a most important and sometimes the most time-consuming part of doing simulations properly. Read widely, and take good notes.<br /><br />Mark