3DNA 1.5

3DNA is a versatile package for analyzing and rebuilding three-dimensional nucleic acid structures, based on a standard reference frame.

In its core, the software uses a simple, yet mathematically rigorous and geometrically sensible, scheme for calculating a complete set of local base-pair, step, and helical parameters, and allows for exact rebuilding of a structure based on these parameters.

Unique features of 3DNA include automatic classification of a dinucleotide step as A-, B-, or TA-like based on the positioning of the phosphorus atoms, and the generation of "standardized" base stacking diagrams. The rebuilding routines give Calladine-Drew style schematic representations of DNA as well as full atomic models with the sugar-phosphate backbone.