Model cary eclipse

The measurements of fluorescence spectroscopy and surface hydrophobicity were performed on a fluorescence spectrophotometer (Model Cary Eclipse, Varian Inc., Palo Alto, CA, USA) referring to the reported methods [20 (link),41 (link)]. For fluorescence spectroscopy, the excitation wavelength and emission wavelength were set 280 nm and 290–450 nm, respectively (slit widths = 5 nm). ANS was used as fluorescent probe to determine surface hydrophobicity of colloidal particle suspension. In brief, colloidal particle suspensions were diluted to 0.075, 0.15, 0.3, 0.6, 1.2 mg/mL with distilled water. Subsequently, 4 mL of diluted protein suspension with 20 μL of 8 mM ANS was used for the analysis of surface hydrophobicity. The fluorescence intensity was measured at the emission wavelength and excitation wavelength, respectively, at 470 nm and 390 nm, and the slit widths were 5 nm each. We used 4 mL of distilled water with 20 μL of ANS in the absence of colloidal particle suspension as blank. The slope of the linear plot of net fluorescence values versus protein concentrations was used as an index of the protein surface hydrophobicity.

According to a previous method (19 (link), 20 (link)), a fluorescence spectrophotometer (Model Cary Eclipse, Varian Inc., Palo Alto, CA, United States) was used to determine fluorescence spectroscopy and surface hydrophobicity. For fluorescence spectroscopy, the emission wavelength ranged from 290 to 450 nm and the excitation wavelength was 280 nm (slit width = 5 nm). Furthermore, for surface hydrophobicity, a fluorescent probe named 8-8′-Diphenyl-5,5′-dinaphthalene disulfonate (ANS) was used to study the structure and behavior of zein. In brief, colloidal particle suspensions were diluted with distilled water to different concentration gradients. Then, the diluted protein suspensions with the volumes of 4 mL and 20 μL of 8 mM ANS were mixed to aid in analyzing surface hydrophobicity. Subsequently, 470 and 390 nm emission wavelength and excitation wavelength, respectively, were selected for the measurement of fluorescence intensity. The slope of the linear plot of the net fluorescence values versus protein concentrations was used to index the protein surface hydrophobicity.

Intrinsic fluorescence spectra of β‐d‐glucosidase solution, untreated or treated with ultrasound, were recorded at room temperature (20 ± 1°C) on a fluorescence spectrophotometer (Varian Inc.; Model Cary Eclipse) at 280 nm (excitation wavelength, slit 5 nm) and 290–500 nm (emission wavelength, slit 5 nm), at a scanning speed of 1000 nm/s. The buffer used to dissolve β‐d‐glucosidase served as the blank (Huang, Wei, Mo, Wang, & Ma, 2017).