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Thermal perturbation techniques in characterizing ligand–macromolecule interactions: Theory and application to the proflavin‐α‐chymotryspin system
Author(s) -
Sturgill Thomas W.,
Johnson Robert E.,
Biltonen Rodney L.
Publication year - 1978
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1978.360170712
Subject(s) - macromolecule , chemistry , thermodynamics , perturbation (astronomy) , thermal , logarithm , derivative (finance) , ligand (biochemistry) , perturbation theory (quantum mechanics) , computational chemistry , physics , quantum mechanics , mathematical analysis , mathematics , biochemistry , receptor , financial economics , economics
A thermal perturbation curve (TPC) is defined to be the derivative of the fractional degree of saturation, f , with respect to temperature, considered as a function of the natural logarithm of free ligand concentration, y . The theoretical framework for the use of such curves in the thermodynamic analysis of ligand binding to macromolecules is presented. The thermal perturbation curve either provides or complements the information obtained from the derivative binding isotherm ∂ f /∂ y . For a single set of identical and independent sites the TPC is identical to the derivative binding isotherm. Analysis of such a curve directly yield Δ H 0 and Δ G 0 for the binding reaction. In actual experimental work, however, the TPC can only be approximated because of “self‐buffering” effects relations between the parameter of the approximate curve and the thermodynamic quantities have been developed. This technique is applied to the proflavin‐α‐chymotryspin system to demonstrate its usefulness. The general features of thermal perturbation curves for cases of multiple sets of independent sites and cooperatively interacting sites have also been developed. The analysis of thermal perturbation curves in combination with other methods should provide a more powerful approach to the characterization of ligand‐macromolecule interactions.