Biopolymers and cell. 2002; 18 (5): 401 - 405

Study of cruciform structure in supercoiled pUCS plasmid DNA by atomic force microscopy and computer modelling

A. P. Limansky

The cruciform structure in supercoiled pUCS plasmid DNA immo¬bilized on aminomodified mica in buffer solution after sample drying was imaged by atomic force microscopy (APM). The cruciform structure was formed by 15 nucleotides inverted repeats as shown from AFM images of DNA. The computer modelling has revealed the cruciform structure to be formed by 11 nucleotides hairpins and 4 bases loops. Free energy of the hairpin was determined to be -17.8 kcal/mol.