<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Rongjian,<div class=""><br class=""></div><div class=""> Here is some python that you can open in Chimera (File / Open) that will load an atomic model (PDB 1a0m) and density map (x-ray map for 1a0m) and print the density map grid index of each atom. The index is floating point since the atoms of course are not exactly at grid points.</div><div class=""><br class=""></div><div class=""> The Chimera Python scripts web page has more example code</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="http://plato.cgl.ucsf.edu/trac/chimera/wiki/Scripts" class="">http://plato.cgl.ucsf.edu/trac/chimera/wiki/Scripts</a></div><div class=""><br class=""></div><div class=""> Tom</div><div class=""><br class=""></div><div class=""></div></body></html>