title: Binding of PFOS to serum albumin and DNA: insight into the molecular toxicity of perfluorochemicals.
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%.
  
  
  CONCLUSIONS
  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.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China. zhangwxian1001@yahoo.com.cn
authors.forename: Xian
authors.initials: X
authors.lastname: Zhang
authors.forename: Ling
authors.initials: L
authors.lastname: Chen
authors.forename: Xun-Chang
authors.initials: XC
authors.lastname: Fei
authors.forename: Yin-Sheng
authors.initials: YS
authors.lastname: Ma
authors.forename: Hong-Wen
authors.initials: HW
authors.lastname: Gao
mesh_terms: D017738:Alkanesulfonic Acids / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D004247:DNA / Q000378:metabolism*; D004573:Electrolytes; D005453:Fluorescence; D005466:Fluorocarbons / Q000378:metabolism / Q000633:toxicity*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D012256:Riboflavin / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism*; D013696:Temperature; D013816:Thermodynamics; D014364:Tryptophan / Q000032:analysis
chemical_list: D017738:Alkanesulfonic Acids; D004573:Electrolytes; D005466:Fluorocarbons; D012709:Serum Albumin; D014364:Tryptophan; D004247:DNA; C076994:perfluorooctane sulfonic acid; D012256:Riboflavin