Release Kinetics of Nicotinamide from Fatty Acid-Nicotinamide Equipmolar Complexes. II. Activation Thermodynamic Quantities

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The rates of release of nicotinamide (NAA) from fatty acid (FA)-NAA complexes, FA-NAA, were determined at various temperatures, and the thermodynamic quantities for the release of NAA were estimated. The results were compared with the previous results obtained for FA-thiamine disulfide (TDS) complexes, (FA)_6(TDS). The values of activation enthalpy (ΔH^〓) and activation entropy (ΔS^〓) for the releaes of NAA from FA-NAA were positive and negative, respectively, indicating that the release of NAA is disadvantageous from not only enthalpic but aso entropic viewpoints. The plots of ΔH^〓 against the carbon number (n) in the constituent FA showed a zig-zag line wiht an upward convex at an odd-numbered position and teh polts of the absolute values of ∣-Δ^〓∣ showed a zig-zag line wiht a downward convex at an odd-numbered position, through the positive values ΔH^〓 increases and the negative value of ΔS^〓 decreases with an increasing n for either even-numbered or odd-numbered FA. It was found that the release of NAA from FA-NAA formed with odd-numbered FA is more disadvantageous enthelpically but more advantageous entropically as compared with that from FA-NAA formed with even-numbered FA. THis phenomenon was simillar to that observed for (FA)_6(TDS). Furthermore, it is suggested that FA-NAA is formed at least by van der Waals forces and hydrophobic interactions and that van der Waals forces are dominant for the formation of FA-NAA formed with odd-numbered FA and that hydrophobic interactions are dominant for the formation of FA-NAA formed with even-numberes FA.
公益社団法人日本薬学会の論文
1991-12-25

Release Kinetics of Nicotinamide from Fatty Acid-Nicotinamide Equipmolar Complexes. II. Activation Thermodynamic Quantities

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