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Science 5 May 1978:
Vol. 200. no. 4341, pp. 531 - 533
DOI: 10.1126/science.644311
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Articles

Science, Vol 200, Issue 4341, 531-533
Copyright © 1978 by American Association for the Advancement of Science

articles

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

R Rudman, D Eilerman, and SJ La Placa

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 Pn21a, 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.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)