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Experimental thermodynamics of the helix–random coil transition. II. Calorimetric measurement of transition enthalpies of poly A in acid aqueous solution
Author(s) -
Klump H.,
Ackermann Th.,
Neumann E.
Publication year - 1969
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.1969.360070313
Subject(s) - chemistry , aqueous solution , enthalpy , protonation , helix (gastropod) , absorption (acoustics) , thermodynamics , calorimetry , transition temperature , random coil , circular dichroism , crystallography , organic chemistry , materials science , ion , ecology , physics , superconductivity , quantum mechanics , biology , snail , composite material
The enthalpy change accompanying the double helix–coil transition of polyriboadenylic acid (poly A) in aqueous solution has been measured optically and calorimetrically in the pH range 5.7–4.5. The course of this cooperative transition was followed optically by measuring changes in ultraviolet absorption as a function of temperature at different pH values, and calorimetrically by determining the heat capacity of the solution through the transition region. From the latter measurements, the enthalpy of transition was calculated. It is shown, that Δ H is dependent on pH as it is expected from the influence of protonation of the double helix of poly A.