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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.

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]

Big data driven data-intensive scientific discovery, and the Big Earth Data is the base and engine of Earth system science. Based on observation of natural geographical elements on different scales and acquisition of data, and the data obtained during the interdisciplinary research processes, integration and mining analysis will promote the development of Earth science to achieve significant innovation. The Big Earth Data has also become the important national strategic resources, and exerted influence on international cooperation and diplomatic relationship. In this study by means of literature metrology, the Big Earth Data literature from the Science Citation Index (SCI) and Social Science Citation Index (SSCI) was analyzed. According to the global paper output quantity, the influence of countries and institutions, research topic, research hotspot change, international cooperation, and so on, present situation of the Big Earth Data research was revealed. Some suggestions in the future will focus on sharing and integration of developing interdisciplinary Big Earth Data, and in order to improve the Earth science data depth mining theory and method, and to realize analysis, modeling and prediction of complex Earth system, and to support and serve global change and sustainable development. [ABSTRACT FROM AUTHOR]