Thermodynamics of porphyrin binding to human serum albumin using affinity capillary electrophoresis |
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Authors: | Y S Ding B C Lin C W Huie |
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Institution: | (1) Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, 116023 Dalian, China;(2) Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China |
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Abstract: | Summary The interaction thermodynamics of heptacarboxylporphyrin (HCP) and protoporhyrin (PP) with human serum albumin (HSA) was studied
by affinity capillary electrophoresis (ACE) over the temperature range of 25–50°C, where HCP and PP bound to HSAvia 1:1 molecular association. The binding equilibrium constants (pH 7.4, phosphate buffer) for the binding of HCP with HSA were
found to decrease with an increase in temperature, whereas the binding constants of the PP/HSA system appeared to be independent
of temperature changes over the range studied. The van’t Hoff relationship (25–50°C) was found to be linear for the interaction
of either HCP or PP with HSA. However, the interaction thermodynamics for both of these porphyrins with HSA were found to
be quite different. In particular, the interaction of HCP (a hydrophilic porphyrin) with HSA appeared to be based on an enthalpy-driven
process, whereas the binding between PP (a hydrophobic porphyrin) and HSA driven by a favorable change in entropy. The ability
of using ACE to evaluate the interaction thermodynamics of serum proteins (e.g., HSA) with ligands (e.g., porphyrins and related
compounds) should aid in the development of new and more effective photosensitizers in the photodynamic therapy of cancer. |
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Keywords: | Affinitycapillary electrophoresis Porphyrins Human serum albumin Binding constants Thermodynamic parameters |
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