Polyanions and their complexes I. Thermodynamic studies of heparin-azure a complexes in solution

The changes in the absorption spectra of the polyanion (heparin)-dye (azure A) complexes at various anion site-to-cation ratios have been studied in aqueous solution, and the thermodynamic parameters of the interaction evaluated. The enthalpy of complex formation ( ΔH) is −7.3 kcal·mole −1, the entr...

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Published inBiochimica et biophysica acta Vol. 141; no. 2; pp. 374 - 381
Main Authors Young, Michael D., Phillips, Glyn O., Balazs, Endre A.
Format Journal Article
LanguageEnglish
Published Netherlands Elsevier B.V 25.07.1967
Subjects
Binding Sites
Coloring Agents
Heparin
Spectrophotometry
Temperature
Thermodynamics
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ISSN0304-4165
0006-3002
1872-8006
DOI10.1016/0304-4165(67)90112-2

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Summary:The changes in the absorption spectra of the polyanion (heparin)-dye (azure A) complexes at various anion site-to-cation ratios have been studied in aqueous solution, and the thermodynamic parameters of the interaction evaluated. The enthalpy of complex formation ( ΔH) is −7.3 kcal·mole −1, the entropy change ( ΔS) is −8.8 cal·mole −1·deg −1, and the free energy change ( ΔG) at 25° is −4.65 kcal·mole −1. These results show that although the “metachromatic” reaction involves a number of parameters, the observed spectral changes may be attributed to the interaction between anion sites of polyanions and dye counterions.
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ISSN:0304-4165
0006-3002
1872-8006
DOI:10.1016/0304-4165(67)90112-2