IONIC-STRENGTH DEPENDENCE OF THE BINDING OF METHYLENE-BLUE TO CHROMATIN AND CALF THYMUS DNA
Artikel i vetenskaplig tidskrift, 1992

The binding of the intercalating dye methylene blue (MB) to chromatin and to free DNA has been studied as a function of ionic strength at very low binding ratios (1 MB/400 DNA bases) using absorption spectroscopy. With increasing salt concentration MB is displaced from chromatin to a higher extent than from DNA. The free energy change for MB binding to chromatin is found to be approximately 5 kJ/mole lower than for binding to DNA. This difference can be explained by the reduced number of high affinity binding sites in chromatin due to the presence of histone proteins. The difference in binding energy is virtually independent of the degree of chromatin condensation and also of the valence of counter ions, suggesting that neither the affinity for, nor the number of intercalation sites in the linker DNA is markedly changed upon the salt-induced condensation. The unaffected thermodynamics of the linker binding suggests that factors such as DNA superhelicity and the electrostatic influence from the chromatosomes remain unchanged during chromatin condensation.

nucleosome

dichroism

nucleic-acids

transitions

ethidium-bromide

Författare

Per Hagmar

Institutionen för fysikalisk kemi

Stefan Pierrou

Institutionen för fysikalisk kemi

P. Nielsen

Bengt Nordén

Institutionen för fysikalisk kemi

Mikael Kubista

Institutionen för fysikalisk kemi

Journal of Biomolecular Structure and Dynamics

0739-1102 (ISSN)

Vol. 9 4 667-679

Ämneskategorier

Biokemi och molekylärbiologi