Impropers in histidine residues

From: Marc Baaden (baaden_at_smplinux.de)
Date: Sat Aug 02 2008 - 03:56:17 CDT

Hi,

I am working on a system where I had to change the protonation state
of a histidine from HSE to HSP. I was surprised to observe that this
leads to the loss of two improper dihedrals and wonder whether this
is expected or not.

With the HSE residue there are the lines

IMPR NE2 CD2 CE1 HE2 CD2 CG NE2 HD2 CE1 ND1 NE2 HE1
IMPR NE2 CE1 CD2 HE2 CD2 NE2 CG HD2 CE1 NE2 ND1 HE1

whereas for HSP there is

IMPR ND1 CG CE1 HD1 ND1 CE1 CG HD1
IMPR NE2 CD2 CE1 HE2 NE2 CE1 CD2 HE2

Intuitively I would have expected that there are more impropers
with HSP in order to ensure the planarity of the additional hydrogen.

What am I missing?

Thanks in advance,
  Marc Baaden

-- 
 Dr. Marc Baaden  - Institut de Biologie Physico-Chimique, Paris
 mailto:baaden_at_smplinux.de      -      http://www.baaden.ibpc.fr
 FAX: +33 15841 5026  -  Tel: +33 15841 5176  ou  +33 609 843217

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