[phenixbb] ReadySet & phenix.refine problem: NAG-Asn with hydrogen atoms

Zhijie Li zhijie.li at utoronto.ca
Mon Apr 29 16:01:11 PDT 2013


I am refining my structure with hydrogen atoms on (phenix 1.8.2-1309). The protein contains two Asn-linked GlcNAc. I noticed two problems with respect to the NAG-Asn linkage in the presence of hydrogen atoms:

1) After running ReadySet (to add hydrogen to the PDB ab initio), the H1 on the NAG is pointing to the amino group of Asn, ie, the NAG seems to be interpreted as in its alpha anomer instead of beta (should be GlcNAc beta1,N-Asn). This is not really a problem as it doesn't seem to affect the refinement.

2) The H21 in Asn is correctly removed by ReadySet, leaving only H22. However, if I send this PDB to phenix.refine, the refinement will fail almost instantly complaining that H22 of the Asn has an unknown nonbonded energy type symbol. But if I simply change the atom name of H22 to H21, the refinement will proceed to completion with no problem, only leaving an H21 at the position where H22 should be.

I was not sure what caused this error. So I trimmed my PDBs down to the Asn and NAG only, and fed the small PDB to ReadySet and phenix.refine (with an eff file indicating the NAG-Asn linkage) and got the same behavior: H22 on Asn - error; H21 on Asn - OK. 

I hope someone can look into this. Thanks in advance.

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