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

Zhang X, Chen L, Fei XC, Ma YS, Gao HW - BMC Mol. Biol. (2009)

Bottom Line: ITC results showed that all the interactions were spontaneous driven by entropy change.At normal physiological conditions, 1.2 mmol/l PFOS reduces the binding ratio of Vitamin B2 to SA by more than 30%.This work provides a useful experimental method for further studying the toxigenicity of PFCs.

View Article: PubMed Central - HTML - PubMed

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

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.

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The device designed for equilibrium dialysis. (1) – semi-permeable membrane with 12.5 ml of dialysate; (2) – the temperature sensor for maintaining the reaction at constant 37°C; (3) – Dialysis solution 37.5 ml; (4) – water bath at constant 37°C. The apparatus was placed on a thermostated magnetic stirrer (5) and rotary magnets were used to mix solutions (3) and (4) thoroughly. The PFOS concentration in solution (3) was determined from the sampling tube (6).
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Figure 8: The device designed for equilibrium dialysis. (1) – semi-permeable membrane with 12.5 ml of dialysate; (2) – the temperature sensor for maintaining the reaction at constant 37°C; (3) – Dialysis solution 37.5 ml; (4) – water bath at constant 37°C. The apparatus was placed on a thermostated magnetic stirrer (5) and rotary magnets were used to mix solutions (3) and (4) thoroughly. The PFOS concentration in solution (3) was determined from the sampling tube (6).

Mentions: A schematic diagram of equilibrium dialysis experiment was shown in Fig. 8. For equilibrium dialysis assay of PFOS, 12.5 ml mother liquor containing 2.5 ml of B-R buffer, 0.15 mol/l NaCl, a known volume of PFOS and deionized water was pipeted into dialysis bags (1). 37.5 ml of the dialysate solution containing 0.15 mol/l NaCl, 7.5 ml of B-R buffer and deionized water was added to the dialysis bag (3). The temperature of the water bath (4) was kept constant at 37°C by adjusting the thermostat magnetic stirrer (5). 1 ml of the dialysis solution (3) was collected into 5-ml calibrated flask every 2 h from the sampling tube (6). According the above detection method, the PFOS concentrations (cL) of the dialysis solutions were determined. Variation of cL with the dialysis time was shown in Fig. 9B. The dialysis of PFOS remains at equilibrium between 8 and 12 h. After dialysis for 10 hours, 1 ml of the dialysis solution (3) was collected in 5-ml calibrated flasks from every sampling tube (6). According to the detection method above, the absorbance of the dialysis solution was measured at 626 nm. The working standard curve of PFOS was established as shown in Fig. 9A. By five repetitive determinations of 0.200 mmol/l PFOS, the result was 0.199 ± 0.006 mmol/l PFOS. The recovery rates of the detection method are between 96.5 and 102% and the relative standard deviation 3%. The detection method was used for the determination of PFOS in the dialysis equilibrium solution, where no complicated interference substance co-existed.


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

Zhang X, Chen L, Fei XC, Ma YS, Gao HW - BMC Mol. Biol. (2009)

The device designed for equilibrium dialysis. (1) – semi-permeable membrane with 12.5 ml of dialysate; (2) – the temperature sensor for maintaining the reaction at constant 37°C; (3) – Dialysis solution 37.5 ml; (4) – water bath at constant 37°C. The apparatus was placed on a thermostated magnetic stirrer (5) and rotary magnets were used to mix solutions (3) and (4) thoroughly. The PFOS concentration in solution (3) was determined from the sampling tube (6).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2656506&req=5

Figure 8: The device designed for equilibrium dialysis. (1) – semi-permeable membrane with 12.5 ml of dialysate; (2) – the temperature sensor for maintaining the reaction at constant 37°C; (3) – Dialysis solution 37.5 ml; (4) – water bath at constant 37°C. The apparatus was placed on a thermostated magnetic stirrer (5) and rotary magnets were used to mix solutions (3) and (4) thoroughly. The PFOS concentration in solution (3) was determined from the sampling tube (6).
Mentions: A schematic diagram of equilibrium dialysis experiment was shown in Fig. 8. For equilibrium dialysis assay of PFOS, 12.5 ml mother liquor containing 2.5 ml of B-R buffer, 0.15 mol/l NaCl, a known volume of PFOS and deionized water was pipeted into dialysis bags (1). 37.5 ml of the dialysate solution containing 0.15 mol/l NaCl, 7.5 ml of B-R buffer and deionized water was added to the dialysis bag (3). The temperature of the water bath (4) was kept constant at 37°C by adjusting the thermostat magnetic stirrer (5). 1 ml of the dialysis solution (3) was collected into 5-ml calibrated flask every 2 h from the sampling tube (6). According the above detection method, the PFOS concentrations (cL) of the dialysis solutions were determined. Variation of cL with the dialysis time was shown in Fig. 9B. The dialysis of PFOS remains at equilibrium between 8 and 12 h. After dialysis for 10 hours, 1 ml of the dialysis solution (3) was collected in 5-ml calibrated flasks from every sampling tube (6). According to the detection method above, the absorbance of the dialysis solution was measured at 626 nm. The working standard curve of PFOS was established as shown in Fig. 9A. By five repetitive determinations of 0.200 mmol/l PFOS, the result was 0.199 ± 0.006 mmol/l PFOS. The recovery rates of the detection method are between 96.5 and 102% and the relative standard deviation 3%. The detection method was used for the determination of PFOS in the dialysis equilibrium solution, where no complicated interference substance co-existed.

Bottom Line: ITC results showed that all the interactions were spontaneous driven by entropy change.At normal physiological conditions, 1.2 mmol/l PFOS reduces the binding ratio of Vitamin B2 to SA by more than 30%.This work provides a useful experimental method for further studying the toxigenicity of PFCs.

View Article: PubMed Central - HTML - PubMed

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

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.

Show MeSH
Related in: MedlinePlus