Minor groove widths in Å calculated in 3DNA28 based on cross-strand distances of phosphate groups. (A) Minor groove widths in AATT and ATTC sites. (B) Minor groove widths of entire 16 base pair sequences. Symbols used are open circles for AATT-RT29, filled circles for AATT, open squares for ATTC-RT29, and filled squares for ATTC. Dashed lines represent the AATT structures and solid lines, the ATTC structures. Dinucleotide steps are indicated for each structure, with those of the ATTC structure in parentheses.