Hi all, 

Has anyone observed ‘odd’ arginine residues, missing the NH1 atom; and possibly related.. very close Chlorine-arginine (NH1 again) distances.

 

I have a 1.3Å structure and am having trouble getting my head around some very odd density features.

 

I have 2 molecules in the assym.  with the equivalent arg residues showing the same odd feature. 

Seems to be a chlorine binding site – typical mix of hydrophobic and proton rich side chains – but, the NH1 of the particular arginine residue concerned (as I say in both NCS copies) seems to have only 50% occupancy and the chlorine appears to have a 2^nd distinct position closer to the arginine, such that if the NH1 atom were present it would be only 2Å away!

 

?

 

Cheers in advance

 

Dean