Improved curve fitting procedures to determine equilibrium binding constants.
For ligand-biomacromolecule titration experiments it has been traditional practice to extract parameters such as the equilibrium binding constant K and the number of bases per ligand binding site n with relatively labour intensive methods, usually based on single wavelength data, such as the difference method by Rodger and Nordén coupled together with a Scatchard plot. Presented in this paper are both the theory and a least squares fitting method to derive parameters such as K and n more directly from all spectral non-linear experimental data. Both the case of non competitive binding of a metal complex ligand to DNA and the case of displacement by a metal complex ligand of an ethidium marker attached to the DNA are considered. This work may be applied directly to reduce experimental data produced by a spectropolarimeter (for circular or linear dichroism) or a spectrophotometer (for fluorescence or UV-Vis spectroscopy).
Stootman
Frank H
FH
University of Western Sydney, PO Box 1797, Penrith South DC, NSW 1797, Australia. f.stootman@uws.edu.au
Fisher
Dianne M
DM
Rodger
Alison
A
Aldrich-Wright
Janice R
JR
D001665:Binding Sites; D001667:Binding, Competitive; D004247:DNA / Q000737:chemistry; D004996:Ethidium / Q000737:chemistry; D007202:Indicators and Reagents / Q000737:chemistry; D016018:Least-Squares Analysis; D008024:Ligands; D046911:Macromolecular Substances / Q000737:chemistry*; D008433:Mathematics; D008956:Models, Chemical
D007202:Indicators and Reagents; D008024:Ligands; D046911:Macromolecular Substances; D004247:DNA; D004996:Ethidium