Table 1.

Histidine Variants in the Companion Amino Acids Variants Dictionary

CODE	Variant
HIS	HISTIDINE
HIS_LEO2	L-HISTIDINE C-TERMINAL DEPROTONATED FRAGMENT
HIS_LEO2H	L-HISTIDINE C-TERMINAL PROTONATED FRAGMENT
HIS_LEO2H_DHD1	L-HISTIDINE-C-TERMINAL PROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LEO2H_DHE2	L-HISTIDINE-C-TERMINAL PROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED NE2
HIS_LEO2_DHD1	L-HISTIDINE-C-TERMINAL DEPROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LEO2_DHE2	L-HISTIDINE-C-TERMINAL DEPROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED NE2
HIS_LFOH	L-HISTIDINE FREE NEUTRAL
HIS_LFOH_DHD1	L-HISTIDINE-FREE NEUTRAL/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LFOH_DHE2	L-HISTIDINE-FREE NEUTRAL/WITH SIDE CHAIN DEPROTONATED NE2
HIS_LFZW	L-HISTIDINE FREE ZWITTERION
HIS_LFZW_DHD1	L-HISTIDINE-FREE ZWITTERION/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LFZW_DHE2	L-HISTIDINE-FREE ZWITTERION/WITH SIDE CHAIN DEPROTONATED NE2
HIS_LL	L-HISTIDINE - LINKING EMBEDDED FRAGMENT
HIS_LL_DHD1	L-HISTIDINE-LINKING EMBEDDED FRAGMENT/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LL_DHE2	L-HISTIDINE-LINKING EMBEDDED FRAGMENT/WITH SIDE CHAIN DEPROTONATED NE2
HIS_LSN3	L-HISTIDINE N-TERMINAL PROTONATED FRAGMENT
HIS_LSN3_DHD1	L-HISTIDINE-N-TERMINAL PROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED ND1
HIS_LSN3_DHE2	L-HISTIDINE-N-TERMINAL PROTONATED FRAGMENT/WITH SIDE CHAIN DEPROTONATED NE2

Note: The Chemical Component Dictionary is accompanied by a companion dictionary of amino acid variants that provides additional nomenclature information for the protonation states of standard amino acids in N-terminal, C-terminal and free forms. This dictionary also includes common side chain protonation states. It is similar to residue variants used in modeling software such as Charmm (42) and Amber (43).