Solving DNA structures by MERLOT

MERLOT, a molecular replacement computer package, has been successfully used for the determination of initial phases for five different oligonucleotide structures. Two of these, CCGG and CGCGCGTTTTCGCGCG, with 316 and 323 non-H atoms respectively in the asymmetric unit, have been solved ab initio using the MERLOT package. The rest are re-examinations of previously solved DNA oligomer structures, ioCCGG, CGCGAATTCGCG and CGCGAATTbrCGCG, with 160, 486 and 488 non-H atoms in the asymmetric unit respectively. Problems involved in applying the molecular-replacement technique to DNA structures, and their possible solutions, are discussed.