Atom Label Key

Naming Convention for α-amino acids


Atom Label

Description


CMain chain Carbon of amide/acid
CAMain chain α carbon
NMain chain nitrogen of amide/amine
OMain chain Oxygen of amide/acid
HMain chain hydrogen of amide
HAMain chain hydrogen of on the α carbon
CBβ Carbon, first carbon of the sidechain
HB?Hydrogen on the β Carbon. '?' is a number 1,2 or 3
OGOxygen on the β Carbon.
CG?γ Carbon. - the '?' if present is a number 1 or 2

The results are shown. The H from the -OH group on C6 is now on the amino acid side chain. The phosphate group has been transferred to the alcohol carbon of glucose and ADP is the other product.

Histidine


Name3 Letter1 Letter
Histidine HIS H

Unprotonated (base form neutral)
histidine
Protonated (acid form positive)
his3d


Drawn as if part of protein to emphasize the sidechain properties The "Sidechain Polarity" button draws an an envelope around the sidechain that is colored by charge according to the scale above.
The envelope shown here is only for the unprotonated - neutral form of the sidechain.

pKR in H2O= 6.5 Free amino acid Mass = 155 g/M
Probability of being found in a:
α-Helix β-Sheet β-Turn
60% 60% 60%
Special Attributes

This amino acid has a cyclic group called an Imidazole group which has a pK right in the physiological pH range. Therefore its protonation state varies widely depending on the situation and the environment.

In the demonstration below, the histidine is in a short piece of α-helix and the sidechain is exposed to solvent.


In the demonstration below you may "left click and drag" to rotate the molecule "SHIFT left click and drag (up or down)" to make smaller or bigger
Click on the white squares in succession to turn or/off identifying features. Some text describing the issues is in the lower right text box



Atom Label Description

Click an atom to diplay it's identity here


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Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/