CRYSTAL-STRUCTURE AND HUMIDITY-INDUCED PHASE-TRANSITION OF DISODIUM SALT OF ADENOSINE 5'-MONOPHOSPHATE

Crystal structure of disodium adenosine 5'-monophosphate dodecahydrate (Na(2)AMP.12H(2)O) was determined. Crystal data are C222(1), a = 6.87 68(6), b = 19.287(3), c = 41.099(6) Angstrom, and Z = 8. Bases are sta cked to make a columnar structure along the a axis. There exist water layers parallel to the ab and ac planes, and molecular columns are iso lated by the water layers. Sodium ions are coordinated by six water mo lecules, and columnar structure of hydrated sodium ions runs parallel to the molecular column. Phase transition of Na(2)AMP undergoes betwee n 0 to 90% relative humidity by four steps. Coupled with increase or d ecrease of the number of water molecules, cell parameters b and c seem to change.