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The gonad of jellyfish (Rhopilema esculentum Kishinouye), containing high protein content with a rich amino acid composition, is suitable for the preparation of bioactive peptides. Jellyfish gonad was hydrolysed with neutral protease to obtain jellyfish gonad protein hydrolysate (JGPH), which was then purified sequentially by ultrafiltration, gel filtration chromatography, and RP-HPLC. The peptides were characterized with HPLC-MS/MS. One peptide with amino acid sequence Ser-Tyr (SY) was identified and synthesized, which showed good ACE inhibitory and antioxidant activity. The IC50 of this peptide on DPPH, ·OH, super oxygen anion scavenging activities, and ACE inhibitory activity are 84.623 μM, 1177.632 μM, 456.663 μM, and 1164.179 μM, respectively. The anchor in the binding site of SY and ACE C-domain (ACE-C) was obtained by molecular simulations. The results showed that the dipeptide purified from jellyfish gonad protein hydrolysates can be used as functional food material and is helpful in the study of antioxidant and inhibition of ACE.

Herein, we report the preparation of Cu-doped Zn/ZnO composites with carbon modification via a simple replacement-hydrothermal method using Zn powder and CuSO 4 $5H 2 O as raw materials. The as-synthesized composites were characterized by powder X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The results showed that Cu doping promotes crystal growth of ZnO, inhibits phase transfer of metallic Zn to ZnO, enhances the optical absorption in the visible region and reduces the recombination of photogenerated electrons and holes. Interestingly, CO 2 dissolved in solution was converted to carbon adhered onto the composite surface (supported by the XPS data). The abundant carbon species present on the composite surface is favorable for surface chemical reactions because it can trap or adsorb reactants which facilitate the transfer of reactants to active sites. The photocatalytic efficiency of the as-synthesized catalysts was evaluated by the degradation of anthraquinone dye (reactive brilliant blue KN-R) in solution under sunlight irradiation. The degradation results revealed that the Cu-doped Zn/ZnO composites have better photocatalytic activities than those of ZnO and Zn/ZnO. The enhancement of the photocatalytic activity of the composites can be attributed to the existence of Cu doping, the Zn/ZnO hetero-structure and covered carbon on the surface of the photocatalysts, which causes electrons to be easily excited from the valence band to the conduction band and efficient separation of electron-hole pairs, as well as quick surface reactions in doped ZnO. Furthermore, a possible growth mechanism of the Cu-doped Zn/ZnO composites with carbon modification was proposed.