PRECISION NEUTRON DIFFRACTION STRUCTURE DETERMINATION OF PROTEIN AND NUCLEIC ACID COMPONENTS. IV. The Crystal and Molecular Structure of the Amino Acid L-Histidine

摘要: A neutron diffraction study of orthorhombic L-histidine, C6H9N3O2, has been carried out. The structure belongs to space group P212121, with four molecules per unit cell. Cell parameters are: a = 5.175 (5) A, b 7.315 (8) and c 18.75 (2) A. total 618 unique reflections were used in the least-squares refinement leading final conventional R-value 5.8%. atomic coordinates found for non-hydrogen atoms agree well those from previous X-ray (1). molecule is zwitterion form, molecular conformation stabilized by an intramolecular hydrogen bond between ammonium imidazole electrostatic interaction carboxyl oxygen. N-Cα-C-O2group be nonplanar. Distances distances have corrected rigid-body motion. are bonded together bonds form chains c-axis direction crystal. There no protonation ring.