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A quantitative analysis of excluded‐site effects for highly cooperative binding systems
Author(s) -
Ramanathan Brinda,
Schmitz Kenneth S.
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.1978.360170911
Subject(s) - scatchard plot , chemistry , molality , binding site , hill differential equation , ligand (biochemistry) , matrix (chemical analysis) , representation (politics) , thermodynamics , binding constant , matrix representation , mathematics , mathematical analysis , receptor , physics , group (periodic table) , biochemistry , chromatography , exact differential equation , organic chemistry , politics , aqueous solution , political science , first order partial differential equation , partial differential equation , law
Binding isotherms can provide quantitive information regarding the stability of a molecular complex. Theorectical studies in recent years have been directed to systems in which a single ligand can exclude more than one polymer site (excluded‐site effect). This system has minium of thre parameters to describe the binding data: the intrinsic binding constant, B ; the remote‐neighbor cooperative paramaters, σ q and the number of excluded sites, q . It is suggested in the present communication that precise values for these three parameters can be obtained by utilizing the characteristics of two forms of data representation: θ vs ln m and θ/ m vs θ, where θ is the degree of saturation (0⩽θ⩽1) and m is the molality of free ligand. The matrix generation method is used to obtain empirical equations relating the midpoint location and slope at the midpoint of the θ vs ln m plot to the three molecular parameters. A modified Scatchard theory is also presented for highly cooperative systems, which results in an expression relaing the maximum in the θ/ m vs θ plot to the molecular parameters σ q and q , thus providing the third equation for the three unknown parameters. The novel method f analysis is illustrated with the AMP‐poly( L ‐arginine) and oligocytidylate–T7 DNA sstems.