Figure 5.

Scattergrams relating the backbone torsion δ and the deoxyribose pucker described by the pseudorotation phase angle P and magnitude τ. The contours enclose 99.9, 90, 50, 20, 10 and 5% of the assigned steps. Red dots represent the average δ, P and τ values of the NtC classes as they are defined in the golden set. Grey diamonds show the values for unassigned dinucleotides. Only a few deoxyriboses have δ within the physically possible limits 75–165° and P outside the −30 to 210° region associated with C3′-endo and C2′-endo sugar puckers. As expected, the magnitude τ does not discriminate between different sugar puckers. In both graphs, many unassigned dinucleotides acquire atypical δ–P and δ–τ combinations and the respective deoxyriboses are in all likelihood not modelled correctly.