Abstract:Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation.

The absence of a robust cell culture system for hepatitis B virus (HBV) and hepatitis C virus (HCV) infection has limited the analysis of the virus lifecycle and drug discovery. We have established a hepatoma cell line, HLCZ01, the first cell line, to the authors' knowledge, supporting the entire lifecycle of both HBV and HCV. HBV surface antigen (HBsAg)-positive particles can be observed in the supernatant and the lumen of the endoplasmic reticulum of the cells via electron microscopy. Interestingly, HBV and HCV clinical isolates propagate in HLCZ01 cells. Both viruses replicate in the cells without evidence of overt interference. HBV and HCV entry are blocked by antibodies against HBsAg and human CD81, respectively, and the replication of HBV and HCV is inhibited by antivirals. HLCZ01 cells mount an innate immune response to virus infection. The cell line provides a powerful tool for exploring the mechanisms of virus entry and replication and the interaction between host and virus, facilitating the development of novel antiviral agents and vaccines.cell culture model | primary human hepatocytes | cccDNA | interferon | ISGs M ore than 500 million people worldwide are persistently infected with hepatitis B virus (HBV) and/or hepatitis B virus (HCV) and are at risk of developing chronic liver diseases (1). There is no vaccine against HCV, and many patients who are persistently infected by HBV or HCV do not respond to currently available therapies (2, 3). Improved understanding of the biology and pathogenesis of these infections is required for the development of vaccine and antiviral drugs (4). The inability to grow HBV and HCV efficiently in cell culture has presented a major obstacle to understanding the virus lifecycle and pathogenesis and to developing improved therapeutics.HBV is a member of the hepadnavirus families, and its genome is a relaxed circular, partially double-stranded DNA molecule. The negative strand has an invariable length of ∼3.2 kb, and the positive strand is 50-100% of this length. Several key issues about the biology of HBV remain to be explored, including the identification of the cellular receptors, the role of the X gene, and the mechanisms by which the viral minichromosome is formed. Covalently closed circular DNA (cccDNA) is responsible for the establishment of viral infection and persistence. Understanding the mechanisms underlying cccDNA formation and regulation is critical for understanding the HBV pathogenesis and finding a cure for hepatitis B. HepG2.2.15 cells derived from the hepatoma cell line HepG2 transfected with the full genome of HBV have been used to study HBV replication (5). Primary human hepatocytes (PHH) are susceptible to HBV infection (6, 7), but the use of this model is hampered by the limited availability and unpredictable variability of human liver. Several human hepatoma cell lines support HBV replication after HBV DNA transfection, and overexpression of sodium-taurocholate cotransporting polypeptide (NTCP) in HepG2 and Huh7 cells can render these cells able t...

The inhibitory effects of 1,3-diacylglycerol (DAG) on diet-induced lipid accumulation in liver and abdominal adipose tissue of rats were investigated in the present study. Male Sprague-Dawley rats were given free access to diets containing 7 wt% TAG (low TAG), 20 wt% TAG (high TAG), or 20 wt% DAG (high DAG), respectively, for 8 wk. The body weight of rats in the 20% high-TAG group increased significantly, and the weights of their abdominal adipose tissue and liver also showed a significant increase compared with rats in the low-TAG group. However, the high-DAG diet resulted in both a significant reduction in body weight gain (with a decrease of 70.5%) and an increase in the ratio of abdominal fat to body weight (by 127%) compared with the high-TAG diet. As well, the liver TAG and serum TAG levels of the high-DAG group were significantly lower than those of the high-TAG group. These effects were associated with up-regulation of acyl-CoA carnitine acyltransferase (ACAT) and down-regulation of acyl-CoA DAG acyltransferase (DGAT) in the liver. However, no significant difference was observed in the activities of alanine aminotransferase and aspartate aminotransferase among the groups (P > 0.05). The present results indicate that dietary DAG reduced fat accumulation in viscera and body, and these effects may be involved with up-regulation of ACAT and down-regulation of DGAT in the liver.

The feasibility of zinc oxide-catalyzed esterification of natural phytosterols with oleic acid was investigated well by a chemical process. The influences of various reaction parameters were evaluated. Basic solid zinc oxide is the most desirable catalyst due to its high selectivity (more than 90%), reusability, activity and less corrosivity, whereas sterol selectivity with other catalysts, such as H 2 SO 4 , NaHSO 4 and NaOMe, did not exceed 80%. Further results showed that during zinc oxide-catalyzed synthesis, the nature of the acyl donor was of paramount importance with direct esterification with fatty acids, which gives better results with higher conversion rate selectivity and more mild reaction conditions than transesterification with methyl esters. The substrate molar ratio of 2:1 (oleic acid/phytosterol) was optimal. Other parameters such as optimal catalyst load (0.5%) and temperature (170°C) showed a maximum production of steryl esters close to 98% after 8 h. It was also found that the amount of trans fatty acid formed in esterification was low, and the trans fatty acid content (%) in the phytosterol oleate ester fraction (3.26%) was much lower than that in free oleic oil (7.35%), which suggested that fatty acids in esters were more stable than free fatty acids regarding the combination with sterol. Immobilized ZnO could be a promising catalyst for replacing homogeneous and corrosive catalysts for esterification reactions of sterol.

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