M. Frey, T. Koetzle, M. Lehmann
Mar 15, 1973
Citations
4
Influential Citations
125
Citations
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Journal
Journal of Chemical Physics
Abstract
The amino acid L‐tyrosine (C9H11NO3) and its salt L‐tyrosine hydrochloride (C9H11NO3·HCl) crystallize respectively in the space groups P212121, a=6.913(3) A, b=21.118(10) A, c=5.832(3) A, and P21, a=11.083(5) A, b=9.041(4) A, c=5.099(3) A, β=91.82(3) A. Both structures have been refined by neutron diffraction techniques, and all the hydrogen atoms have been located precisely. The tyrosine molecule occurs in the zwitterion form in pure L‐tyrosine while both the amino group and the carboxyl group are protonated in the hydrochloride. In both crystalline compounds there is a three‐dimensional network of hydrogen bonds. Statistical tests show no significant differences between the bond lengths and valence angles in the compounds except for those atoms involved in hydrogen bonds. The conformational angles of the main chain (C, Cα, N, O1, O2) and those of the side chain differ only slightly in the two compounds while the mutual orientations of the main chain and of the side chain differ completely; in L‐tyrosine...