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A calorimetric study of a polymer–monomer complex formed by polyuridylic acid 3′,5′‐cyclic AMP
Author(s) -
Franck F.,
Ackermann Th.
Publication year - 1973
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.1973.360120214
Subject(s) - chemistry , cooperativity , monomer , enthalpy , calorimetry , stoichiometry , mole , thermodynamics , polymer , polymer chemistry , crystallography , organic chemistry , biochemistry , physics
The existence of a soluble complex formed by polyuridylic acid (poly (U)) and 3′,5′‐cyclic AMP (cAMP) is demonstrated by u.v. extinction vs. temperature curves, optical rotation, equilibrium dialysis, and reaction calorimetry. The complex hasthe stoichiometry of 2 poly (U)‐cAMP and its formation is accompanied by an enthalpy change of −13.0 kcal/mole of base triplet. The introuction of an empirical factor α in the equations given by Damle 2 and Crothers 2 leads to the evolution of a Δ H value of −13.4 keal/mole. The parameter α is considered as a correction factor for the concentration dependence of the binding process. There is no relation between α and the reduction of monomer activity due to self‐association of monomers. The study of the binding process at several temperatures showed that the cooperativity parameter, σ, is independent of temperature and its value of 6.5 × 10 −3 is in good agreement with σ = 5 × 10 −3 for the poly (U)·poly(A) system. 3