CONTROL OF NUCLEATION IN OLIGONUCLEOTIDE CRYSTALLIZATION BY THE OSMOTIC DEWATERING METHOD WITH KINETIC WATER REMOVAL RATE CONTROL

Crystallization of an RNA oligonucleotide-''U-U dodecamer'' (dodecamer ) using a kinetically controlled osmotic dewatering method is presente d. A concentration gradient across a reverse osmosis membrane is used to control the water-removal rate from the crystallization solution, B y kinetically adjusting the dewatering rate, the number of crystals ob tained was reduced, and crystal sizes were increased. Experimental res ults suggest that early rapid dewatering is needed to create a RNA-ric h zone to promote nucleation. After the nucleation step, a slower dewa tering rate is applied to suppress further nucleation and to provide a n environment more suitable for crystal growth. The diffraction qualit y of dodecamer crystals grown by kinetically controlled osmotic dewate ring is comparable with that of crystals grown by the hanging drop and silting drop methods. (C) 1998 Elsevier Science B.V. All rights reser ved.