3DNA uses the formula of Altona & Sundaralingam (1972): Conformational Analysis of the Sugar Ring in Nucleosides and Nucleotides. A New Description Using the Concept of Pseudorotation [J. Am. Chem. Soc., 94(23), pp. 8205–8212].
See my blogpost "
Two slightly different definitions of sugar pucker" for a newer set of formula due to Westhof & Sundaralingam (1983): A Method for the Analysis of Puckering Disorder in Five-Membered Rings: The Relative Mobilities of Furanose and Proline Rings and Their Effects on Polynucleotide and Polypeptide Backbone Flexibility. [J. Am. Chem. Soc., 105(4), pp. 970–976].
DSSR can calculate sugar puckering parameters using either of the two sets, depending on a switch. See the
DSSR User Manual for details.
HTH,
Xiang-Jun