Nucleic Acids Research, 1984, Vol. 12, No. 23 9165-9177
© 1984
CHEMISTRY |
Infrared linear dichroism of oriented DNA-ligand complexes prepared with the wet-spinning method
Academy of Sciences of the GDR, Central Institute of Microbiology and Experimental Therapy, Department of Biophysical Chemistry, Jena, GDR Department of Physical Chemistry Stockholm, Sweden +University of Stockholm, Arrhenhis Laboratory, Department of Physical Chemistry Stockholm, Sweden
Received September 6, 1984. Accepted October 4, 1984.
Oriented DNA films prepared by the wet-spinning technique have been complexed with several ligands: the anthracycline antibiotic violamycin BI, the dipeptide L-carnosine, and the oligo-peptide antibiotic netropsin. The formation of the DNA-ligand complexes is accompanied by dramatic changes of the conformational flexibility of DNA. The B-A transition which occurs usually between 80% and 70% relative humidity (RH) is more or less suppressed by the ligands. Violamycin BI at a total ligand per DNA base pair ratio, rt, of {small tilde}0.03 and L-carnosine at rt {small tilde} 1.5 inhibit the B-A transition of {small tilde}18 and {small tilde}0.25 base pairs per ligand molecule, respectively. Netropsin at rt = 0.2 induces a very stable B-DNA even at rather low RH (23%). The total hydration of this complex is significantly higher than for a drug-free DNA film. Netropsin-DNA complexes at rt of 0.02 and 0.01 result in an inhibition of {small tilde}45 base pairs per drug molecule with respect to the B-A transition.