Potential protein toxicity of synthetic pigments: binding of poncean S to human serum albumin
H. W. Gao 1*, Q. Xu 1, L. Chen 1, S. L. Wang 1, Y. Wang 1, L. L. Wu 1 and Y. Yuan 1
1 Tongji University
* To whom correspondence should be addressed. E-mail: hwgao{at}mail.tongji.edu.cn.
Submitted on August 29, 2007
Revised on September 9, 2007
Accepted on 12 September 2007
 |
Abstract |
|---|
Using various methods e.g. spectrophotometry, circular dichroism (CD) and isothermal titration calorimetry (ITC), the interaction of poncean S (PS) with human serum albumin (HSA) was characterized at pH 1.81, 3.56 and 7.40 using the Einstein-Planck formula, spectral correction technique, and Langmuir and Temkin isothermal models. The consistency among results concerning e.g. binding number, binding energy and type of binding showed that ion-pair electrostatic attraction fixed the position of PS in HSA and subsequently induced a combination of multiple non-covalent bonds such as H-bonds, hydrophobic interactions and van der Waals forces. Ion-pair attraction and H-bonds produced a stable PS-HSA complex and led to a marked change in the secondary structure of HSA in acidic media. The PS-HSA binding pattern and the process of change in HSA conformation were also investigated. The potentially toxic effect of PS on the transport function of HSA in a normal physiological environment was analyzed. This work provides a useful experimental strategy for studying the interaction of organic substances with biomacromolecules, helping us to understand the activity or mechanism of toxicity of an organic compound.
Key Words:
human serum albumin, non-covalent binding, protein-ligand interaction
