Biopolymers and cell. 2005; 21 (6): 515 - 524

S-DNA is oversupercoiled macromolecule with ~2 Å rise per nucleotide pair

O. Yu. Limanskaya, L. A. Limanskaya, A. P. Limanskii

The supercoiled pGEMEX DNA with length of 3993 nucleotides was immobilized on different substrates (freshly cleaved mica, standard aminomica, modified aminomica with increased and decreased aminogroups surface density comparing with standard aminomica) and studied by the atomic force microscopy. The DNA molecules with extremely high level of supercoiling were visualized on the modified aminomica with increased surface charge density. The rise per nucleotide pair was determined by measurement of a contour length of single oversupercoiled DNA molecules. The rise value per nucleotide pair varied from H=1.94 Å up to H=2.19 Å for different molecules. These spring-like compressed supercoiled DNA molecules with decreased rise in comparison with well known DNA forms were referred to the new DNA form, called S-DNA.

Key words: supercoiled DNA, atomic force microscopy, aminomica, oversupercoiled DNA, S-DNA.