Research article

Binding of PFOS to serum albumin and DNA: insight into the molecular toxicity of perfluorochemicals

Xian Zhang¹ , Ling Chen¹ , Xun-Chang Fei² , Yin-Sheng Ma³ and Hong-Wen Gao¹

¹State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China

²Key Laboratory of Yangtze River Water Environment of Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai, PR China 200092

³Environmental Engineering College, NanJing Forestry University, Nanjing 210037, PR China

author email corresponding author email

BMC Molecular Biology 2009, 10:16doi:10.1186/1471-2199-10-16

Published:	25 February 2009

Abstract

Background

Health risk from exposure of perfluorochemicals (PFCs) to wildlife and human has been a subject of great interest for understanding their molecular mechanism of toxicity. Although much work has been done, the toxigenicity of PFCs remains largely unknown. In this work, the non-covalent interactions between perfluorooctane sulfonate (PFOS) and serum albumin (SA) and DNA were investigated under normal physiological conditions, aiming to elucidate the toxigenicity of PFCs.

Results

In equilibrium dialysis assay, the bindings of PFOS to SA correspond to the Langmuir isothermal model with two-step sequence model. The saturation binding number of PFOS was 45 per molecule of SA and 1 per three base-pairs of DNA, respectively. ITC results showed that all the interactions were spontaneous driven by entropy change. Static quenching of the fluorescence of SA was observed when interacting with PFOS, indicating PFOS bound Trp residue of SA. CD spectra of SA and DNA changed obviously in the presence of PFOS. At normal physiological conditions, 1.2 mmol/l PFOS reduces the binding ratio of Vitamin B₂ to SA by more than 30%.

Conclusion

The ion bond, van der Waals force and hydrophobic interaction contributed to PFOS binding to peptide chain of SA and to the groove bases of DNA duplex. The non-covalent interactions of PFOS with SA and DNA alter their secondary conformations, with the physiological function of SA to transport Vitamin B₂ being inhibited consequently. This work provides a useful experimental method for further studying the toxigenicity of PFCs.