Hi Dialing,<div><br></div><div>Determining the protonation state of a HIS residue based on the diffraction data would require very high resolution data (below 1.0A), if that is possible at all.</div><div><br></div><div>However, it is possible to determine the protonation state of HIS residues based on the local hydrogen-bonding network for a model at any resolution, assuming it is well built. The program Reduce, which is the program used in Phenix to add hydrogens to a model, does this automatically. Reduce looks at the local hydrogen-bonding network created by neighboring residues and other capable groups (waters, ligands, etc.) and then optimizes the HIS orientation and protonation state. The three possibilities are delta protonated (HD2), epsilon protonated (HE2), or both (HD2 and HE2).</div>

<div><br></div><div>You can read more about Reduce here:</div><div><br></div><div><a href="http://kinemage.biochem.duke.edu/software/reduce.php">http://kinemage.biochem.duke.edu/software/reduce.php</a></div><div><br></div>

<div>Jeff<br><br><div class="gmail_quote">On Fri, Apr 6, 2012 at 4:18 AM, Dialing Pretty <span dir="ltr">&lt;<a href="mailto:hdc123hdc123@yahoo.com">hdc123hdc123@yahoo.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">

<div><div style="font-size:14pt;font-family:times new roman,new york,times,serif"><div><span>Dear All,</span></div><div><span></span> </div><div><span>There may be PDB files which shows different protonation  state of HIS, at least there is PDB file shows double protonated HIS. At which resolution of the crystal<var></var> can allow us to distinguish different protonation states of HIS?</span></div>

<div><span></span> </div><div><span>How do Phenix and Coot give different protonation states of HIS?</span></div><div><span></span> </div><div><span>I am looking forward to getting your reply.</span></div><div><span></span> </div>

<div><span>Cheers,</span></div><div><span></span> </div><div><span>Dialing</span></div>   </div></div><br>_______________________________________________<br>
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