The structure of crystalline tris: A plastic crystal precursor, buffer, and acetylcholine attenuator

Abstract

The crystal and molecular structure of the widely used buffer tris(hydroxymethyl)aminomethane (tris) has been determined from single-crystal diffractometer data to a standard agreement factor (R value) of 0.026 and bond length standard deviations of 0.002 angstrom. Tris crystallizes in the orthorhombic system, space group Pn2 1a, with four molecules per unit cell; a = 8.844(1) angstroms, b = 7.794(1) angstroms, and c = 8.795(1) angstroms. The center-to-center distances of tris molecules in the ordered phase range from 0.4 to 1.0 angstrom less than they do in the orientationally disordered (plastic) phase of similar molecules. Copyright © 1978 AAAS.