AMBER Archive (2009)

Subject: Re: [AMBER] Histidine, which form?

From: Carlos Simmerling (
Date: Mon Jun 15 2009 - 09:57:40 CDT

the delta N is the one closer to the alpha carbon- atoms are labeled in
order alpha, beta, gamma, delta, epsilon moving out the side chain. not sure
what you mean by an example of HIP- this would be His at low pH. most x=-ay
crystal structures have no H atoms so it is not clear which of the 3 forms
it really is. you need other experiments to tell.

On Mon, Jun 15, 2009 at 10:54 AM, <> wrote:

> Dear AMBER
> For Histidine, there are three forms of it, HIE, HID, and HIP.
> Delta poistion is position number 1 and Epsilon Position is position number
> 3.
> The problem is that:
> There two different systems of numbering the atoms in the
> imidazole ring of histidine had both been used for a considerable time
> (biochemists
> generally numbering as 1 the nitrogen atom adjacent to the side chain, and
> organic chemists
> designating it as 3).
> So, could you tell me which nitrogen atom is the delta one, please?
> Also, could you give me an example of HIP when histidine is protonated on
> both positions, please?
> Thanks in Advance
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