Data for β-lactoglobulin conformational analysis after (-)-epigallocatechin gallate and metal ions binding

This data article contains complementary results related to the paper “Effect of metal ions on the binding reaction of (-)-epigallocatechin gallate to β-lactoglobulin” (Zhang et al., 2017) [1]. Data was obtained by circular dichroism (CD) spectroscopy to investigate potential β-lactoglobulin (β-Lg) conformational changes with different concentrations of EGCg and Cu2+ or Al3+ added to β-Lg. 500 µL of the 25 µM β-Lg solution containing EGCg (25 µM) or metal ions (0–500 µM) were measured, and the spectra were recorded. CD spectroscopy data present in this article indicated that the β-Lg-Cu, β-Lg-Al and β-Lg-EGCg interaction resulted in unfolding of the secondary structure of β-Lg.


a b s t r a c t
This data article contains complementary results related to the paper "Effect of metal ions on the binding reaction of (-)-epigallocatechin gallate to β-lactoglobulin" (Zhang et al., 2017) [1].
Data was obtained by circular dichroism (CD) spectroscopy to investigate potential β-lactoglobulin (β-Lg) conformational changes with different concentrations of EGCg and Cu 2 þ or Al 3 þ added to β-Lg. 500 mL of the 25 mM β-Lg solution containing EGCg (25 mM) or metal ions (0-500 mM) were measured, and the spectra were recorded. CD spectroscopy data present in this article indicated that the β-Lg-Cu, β-Lg-Al and β-Lg-EGCg interaction resulted in unfolding of the secondary structure of β-Lg. CD spectroscopy was performed with the method of Li et al. [2].

Experimental features
All samples were prepared in 20 mM PBS buffer at pH 7.4. 500 mL of the 25 mM β-Lg solution containing EGCg (25 mM) or metal ions (0-500 mM) were measured, and the spectra were recorded.

Nanjing, China
Data accessibility Data is with this article

Value of the data
The data provides some additional data on the effects of metal ions on the binding reaction of EGCg to β-Lg.

Materials
EGCg (Z95%) and β-Lg (A variant, purity Z90%) were purchased from Sigma-Aldrich Co. (St. Louis, MO, USA). Working solutions of EGCg (0.25 mM) were prepared by dissolving the EGCg in a 50% methanol solution. The working solution of β-Lg (25 mM) was prepared in 20 mM PBS buffer, pH 7.4 and stored in a refrigerator prior to use. The β-Lg and EGCg concentrations were determined spectrophotometrically by their extinction coefficients: ε 280 (β-Lg)¼ 17600 M À 1 cm À 1 and ε 280 (EGCg)¼ 9700 M À 1 cm À 1 at 280 nm [4,5]. For in vitro experiments, the working solutions of Cu 2 þ and Al 3 þ (1.0 mM) were prepared by dissolving CuCl 2 Á 2H 2 O and AlCl 3 , respectively, in double-distilled water containing 0.1 M HCl to facilitate dissolution. All other reagents and solvents were of analytical reagent grade and used without further purification. All aqueous solutions were prepared using freshly double-distilled water.

Experimental design
CD spectroscopy was performed using a MOS-500 spectropolarimeter (Bio-Logic, France) with the modified method of Li et al. [2]. The CD spectra of the β-Lg, [β-Lg-EGCg] and [β-Lg-metal] systems were recorded between 190 and 250 nm by scanning the spectrum at 25°C, with a scanning speed of 100 nm min À 1 , 2 s response time, and 1.0 nm step size. All samples were prepared in 20 mM PBS buffer at pH 7.4. To investigate the effect of EGCg, Cu 2 þ and Al 3 þ on the secondary structure of β-Lg, 500 mL of the 25 mM β-Lg solution containing EGCg (25 mM) or metal ions (0-500 mM) were measured, and the spectra were recorded. The samples were loaded into a rectangular quartz cuvette with a path length of 1 mm. The spectra of three consecutive scans were averaged and corrected by subtracting the solvent/buffer spectra.