| Abstract: | Compactization of supercoiled circular plasmid pBR322 caused by interaction with synthetic oligopeptide dansyl hydrazide trivaline capable of beta-structure formation was studied by electron microscopy. The results show that at rising input peptide concentration circular DNA molecules undergo intramolecular structural transition with the formation of compact ring structures. The compact ring structures are formed by the fiber having the thickness of 60 A. The analysis of morphology of intermediate structures and the contour length measurements enable us to conclude that 60 A-fiber contains three lying side-by-side and interwound double-stranded DNA segments. Thus, the compact ring structures are addressed to as triple rings. The triple ring have one special point, where the triple region ends are locked by a duplex DNA segment. The mechanisms responsible for the triple ring formation may be of importance for DNA and chromatin compactization processes in vivo. |
