Models of triple-stranded polynucleotides with optimised stereochemistry

Detailed models are presented for the triple-stranded polynucleotide helices of poly(U).poly(A).poly(U) (two forms), poly(U).poly d(A).poly(U), poly d(C).poly d(I).poly d(C), poly d(T).poly d(A).poly d(T) and poly(I).poly(A).poly(I). The models were generated using a computerized, linked-atom procedure which preserves standard bond lengths, bond angles and sugar ring conformations, constrains the helices to have the pitches and symmetries observed in X-ray diffraction experiments, and optimises the non-bonded interatomic contacts including hydrogen bonds. The possible biological significance of such complexes is discussed.