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Histidine H (His)

Chemical Properties:
    Basic
(Basic group) 		Physical Properties:
    Polar (positively charged)
   


Histidine, an essential amino acid, has as a positively charged imidazole functional group.

The imidazole makes it a common participant in enzyme catalyzed reactions. The unprotonated imidazole is nucleophilic and can serve as a general base, while the protonated form can serve as a general acid. The residue can also serve a role in stabilizing the folded structures of proteins.
molecular structure for histidine NH-CH=N-CH=C-CH2-CH(NH3)-COO
Chemical structure of histidine

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The Biology Project > Biochemistry > The Chemistry of Amino Acids

The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
August 25, 2003
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