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To explore the effect of a chitosan-based preservative solution (10 mg/mL chitosan + 5 mg/mL tea polyphenol + 2 000 U/mL lysozyme) on the change in the muscle proteome of grass carp during cold storage, differential proteomic analysis of fresh fish and nine-day-stored fish with or without (control) preservative treatment was conducted by two-dimensional electrophoresis-mass spectrometry (2DE-MS). The results showed that the 2DE map of the preservative-treated group was not obviously different from that of the fresh group, except for a decrease in the abundance of fast troponin T and an increase in the abundance of slow troponin T and adenylate kinase isoenzyme. However, the 2DE profile of the control group differed greatly from that of the fresh group in both the number and signal intensity of protein spots. Further analysis showed that the abundance of fast troponin T, tropomodulin 4, synaptopodin 2 and pyruvate kinase type M were down-regulated, while the abundance of myosin heavy chain, myosin light chain 1, α-actin, α-tropomyosin and intermediate light meromyosin were up-regulated. Moreover, compared with the preservative-treated group, the abundance of three troponins T were decreased, while the abundance of myosin heavy chain, intermediate light meromyosin, α-actin, α-tropomyosin and creatine kinase M-type were increased in the control group, suggesting that creatine kinase could serve as an indicator for evaluating grass carp muscle spoilage. This study demonstrates that the chitosan-based composite preservative can maintain the stability of grass carp muscle protein during cold storage.

Using first‐principles calculations, two C4N monolayers with a zigzag buckled (ZB) structure are proposed. The ZB C4N monolayers contain raised‐C (raised‐N) atoms with sp3 hybridization, different from the traditional 2D graphene‐like carbon nitride materials with sp2 hybridization. Interestingly, the band structures of the ZB C4N monolayers exhibit quasi‐1D Dirac nodal line resulting from the corresponding quasi‐1D structure of the zigzag carbon chains, which is essentially different from the conventional ring‐shaped nodal line. The quasi‐1D Dirac nodal line exhibits the following features: i) gapless Dirac points, ii) varying Fermi velocity, and iii) a slightly curved band along the high‐symmetry path. All these features are successfully explained by the proposed tight‐binding model that includes interactions up to the third nearest neighbor. The Fermi velocity of the 2D system can reach 105 m s−1, which is promising for applications in high‐speed electronic devices. The topological flat band structure of the corresponding 1D system determined by the Zak phase and band inversion is edge‐dependent, which is a weak topological state and can be explained by the 2D Su‐Schrieffer‐Heeger (SSH) model. The quasi‐1D Dirac Fermions and SSH edge states make the ZB C4N monolayers promising for nanoelectronics applications. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the reaction mechanism of wulfenite with an aqueous sodium sulfide solution and thereby provide guidance for the sulfidization flotation and sodium sulfide leaching of wulfenite. For this purpose, dissolution/leaching behavior analysis, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FESEM) were performed. The dissolution/leaching analysis indicated that sodium sulfide can induce the dissolution of PbMoO4. The XRD and Raman spectra results demonstrated that PbMoO4 was replaced by PbS at the wulfenite–sodium sulfide solution interface, and the sulfidized wulfenite particles had a PbMoO4/PbS core–shell structure. The XPS results also indicated the transformation of PbMoO4 to PbS. The FESEM images showed the growth of PbS nanoparticles on the surface of wulfenite and the dissolution pits after treatment with sodium sulfide solution. These findings showed that wulfenite sulfidization proceeds through an interface-coupled dissolution–precipitation mechanism. In the presence of sodium sulfide solution, the less stable PbMoO4 dissolves, and the more stable PbS phase precipitates, both of which are coupled at the wulfenite–sodium sulfide aqueous solution interface. [ABSTRACT FROM AUTHOR]

To solve the problem of poor thermal stability of the current D-allulose 3-epimerase (DAEase), the ancestor sequences of DAEase with different catalytic domains were reconstructed by big data mining, reasonable modification and ancestor sequence reconstruction (ASR) strategy under the guidance of phylogenetic information. The expression vectors of the ancestor sequences were constructed, and DAEase A13 with significantly enhanced thermal stability was screened by recombinant expression and molecular docking, and its enzymatic properties were characterized. In addition, the molecular mechanism of thermal stability enhancement of DAEase A13 was revealed based on structural analysis and molecular dynamics. The results showed that the half-life of A13 constructed based on ASR strategy could reach 8.4 h at 70 °C, indicating that its thermal stability was significantly enhanced compared with that of wild-type (WT) enzyme. The maximum conversion rate of A13 reached 31%, indicating that the catalytic activity of A13 was slightly higher than that of WT enzyme. The structural and molecular dynamics analysis revealed that the increase in hydrogen bonding and hydrophobic interaction in ASR A13 was the main factor responsible for maintaining the stability of the enzyme's molecular structure at high temperatures. The results showed that ASR strategy could modify DAEases to enhance the stability, activity or hybridity, which could provide superior biocatalyst sources for various industrial applications of functional sugars. [ABSTRACT FROM AUTHOR]

This study describes the first, use of eco-friendly welan gum as a new depressant in galena-pyrite flotation separation. The depression mechanism were examined using micro-flotation and various characterization techniques. The selective depression performance of welan gum on pyrite was found to effectively enhance the galena/pyrite flotation separation index. Compared with the addition of NaBX alone, the grade of Pb in the produced concentrate increased by more than 28% (from 40.86% to 70.02%). And it was possible to recover 87.79% of galena and only 15.98% of pyrite. There was an accentuated increase in the electronegativity of the pyrite surface by more than ~ 8 mV after treatment with welan gum alone compared to an increase of ~ 1 mV for galena, which can be explained by the fact that welan gum selectively adsorbed on the pyrite surface in significant amounts. As a result, the subsequent adsorption of xanthate is prevented. This finding has been further proven by adsorption measurement results. The X-ray photoelectron spectroscopy and Time-of-Flight secondary ion mass spectrometry results indicated that the hydroxyl groups in welan gum showed acid – base interactions with the metal hydroxylated species anchored on the mineral surfaces, which may be the main driving force in the adsorption process. Differences in the amount of metal hydroxide on the mineral surface, as well as the electrical affinity of metal ions in metal hydroxide, contributed to the selective adsorption of welan gum. Therefore, welan gum can be regarded as a potential pyrite-depressant. [ABSTRACT FROM AUTHOR]