Data on the fluorescence quenching analysis of BSA induced by pyrene and/or 1-hydroxypyrene in binary and ternary systems

This article present data related to the publication entitled “Interactions of pyrene and/or 1-hydroxypyrene with bovine serum albumin based on EEM-PARAFAC combined with molecular docking” (Zhang et al., 2018) [1]. The excitation-emission matrix (EEM) fluorescence spectral parameters of pyrene, 1-hydroxypyrene, bovine serum albumin (BSA), and their mixtures were presented in this article. Combined EEM - parallel factor analysis with fluorescence quenching analysis, some data related to the binding affinity of pyrene and/or 1-hydroxypyrene with BSA in the binary and ternary systems were obtained.


Subject area
Chemistry More specific subject area Analytical chemistry Type of data For all of the excitation-emission matrix (EEM) spectroscopy measurements, different concentrations of Pyrene, 1-hydroxypyrene, and BSA were prepared in 0.05 mol L À 1 Tris-HCl buffer (pH ¼ 7.40, containing 0.10 mol L À 1 NaCl), with each containing ethanol of no more than 0.5‰.

Experimental features
Combined with EEM fluorescence spectra with parallel factor analysis to investigate the binding ability of BSA with pyrene and/or Value of the data • The EEM data showed that the spectra of pyrene, 1-hydroxypyrene and BSA overlap, and this work provided the way to solve it, which may provide an insight to study other similar ternary interaction systems. • The data showed the difference of the binding affinity of pyrene or 1-hydroxypyrene with BSA both in the binary and ternary systems, which was helpful for readers to compare the binding affinity of pyrene or 1-hydroxypyrene with BSA. • The data may be further helpful for understanding the combined toxicity of pyrene and 1-hydroxypyrene.  Table 1 showed the EEM fluorescence spectral parameters of Pyr (6.0 Â 10 À 7 mol L À 1 ), 1-OHPyr (7.5 Â 10 À 7 mol L À 1 ), BSA (1.0 Â 10 À 6 mol L À 1 ), and their mixtures. The range of excitation/emission wavelengths of Pyr, 1-OHPyr, BSA, and their mixtures, and the maximum excitation/emission wavelength of each were presented. As can be seen, the excitation spectra of Pyr were in the range of 260-278 and 295-340 nm, with the emission spectra ranging from 370 to 440 nm; for 1-OHPyr, its excitation spectra ranged from 260 to 290 nm and 310 to 370 nm, with the emission spectra ranging from 380 to 440 nm; however, excitation spectra of BSA ranged from 250 to 310 nm, with the emission spectra in the range of 290-450 nm. The data indicated that the EEM spectra of the mixed system of BSA, Pyr, and/or 1-OHPyr overlap severely.

Fluorescence quenching data of BSA by Pyr and 1-OHPyr in the binary and ternary systems using Stern-Volmer plots
After using the parallel factor analysis to decompose the EEM spectra of complex systems of Pyr, 1-OHP and BSA, the fluorescence properties of each individual component were obtained [1]. Combined with the fluorescence quenching method, the interactions of BSA with Pyr and 1-OHPyr in binary and ternary interaction systems were further studied. The measured fluorescence quenching data of BSA by Pyr and 1-OHPyr in the binary and ternary systems were fitted by Origin 7.5 based on Stern-Volmer plots (Eq. (1)) ( Fig. 1) [2], and corresponding values were listed in Table 2.   a C BSA ¼ 1.0 Â 10 À 6 mol L À 1 ; C 1-OHPyr ¼ 7.5 Â 10 À 7 mol L À 1 ; C Pyr ¼ 6.0 Â 10 À 7 mol L À 1 F 0 and F are the relative fluorescence intensities of BSA in the absence and presence of Pyr or 1-OHPyr, respectively; [Q] is the concentration of Pyr or 1-OHPyr, K sv is the Stern-Volmer quenching constant, and K q is the quenching rate constant. Fig. 2 showed the double logarithm plots for the quenching of BSA by Pyr and 1-OHPyr in binary and ternary systems. The binding constant (K b ) and the number of binding sites (n) of Pyr and 1-OHPyr with BSA in binary and ternary interaction systems could be calculated by fitting the curve based on Eq. (2) [3,4].
2. Experimental design, materials, and methods

Materials
BSA (purity 4 99.5%), Pyr (purity 4 98%) and 1-OHP (purity 4 99%) were purchased from Sigma Chemical Company (St. Louis, MO, USA) and were used without further purification. Stock solutions of 4.0 Â 10 À 5 mol L À 1 BSA were prepared in 0.05 mol L À 1 Tris-HCl buffer (pH ¼ 7.40, containing 0.10 mol L À 1 NaCl). Stock solutions of 1-OHP and Pyr were prepared individually in ethanol at concentrations of 2.0 Â 10 À 3 mol L À 1 . The stock solutions were stored at 277 K in the dark. All of the other chemicals that were used were of analytical reagent grade. Milli-Q water (18.2 MΩ cm) was used throughout the study.

PARAFAC analysis
Using MATLAB R2016b software (the MathWorks, Inc., Natick, MA, USA), the EEM dataset (size of 33 Â 111 Â 35) was decomposed by the PARAFAC method, according to the procedures described by Ref. [5]. First, the EEM spectra of the samples were corrected by subtracting the EEM spectra of the blank samples (Tris-HCl buffer) and removing the Rayleigh scattering and the two order Raman scattering peaks to reduce the scattering light and other background interference. Second, the 2-8 component model is used to decompose the EEM dataset by trilinear decomposition. To reduce the time of Matlab analysis, the relative fluorescence intensity values of the 35 EEM spectra were reduced by 100 times; thus, the relative fluorescence intensity values of the three components reported in this section were 0.01 times their practically measured values. Finally, the relative fluorescence intensity values of BSA obtained were used for the fluorescence quenching analysis.

Acknowledgments
We gratefully acknowledge the financial support of the National Major Scientific Instruments Devel-