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91.
宝丹酮作为一种重要的蛋白同化雄性激素类固醇,具有提升肌肉质量和耐力的功能。宝丹酮的传统合成方法是以1,4-雄烯二酮(ADD)为底物通过化学法合成,但过程复杂、污染严重。17β-羟基类固醇脱氢酶(17β-HSD)可催化甾体化合物C-17位点的氧化还原反应,实现ADD和宝丹酮的相互转化。本研究通过基因序列同源性分析,筛选到6种不同来源的17β-HSD基因并对其在大肠杆菌中进行异源表达。利用不同重组菌转化ADD合成宝丹酮,结果表明重组菌BL21/pET28a-HSDPy的ADD转化率最高,因此选择BL21/pET28a-HSDPy进行进一步研究。鉴定了重组菌的酶学性质并优化其全细胞转化条件。结果表明在生物量为36 g·L-1、底物浓度为5.40 g·L-1条件下,经过两次补料,获得了3.66g·L-1宝丹酮,比优化前提高了4.1倍。而且在生物转化过程中未检测到副产物。为生物合成宝丹酮提供了可能。 相似文献
92.
Georgina K. SuchAngus P.R. Johnston Kang LiangFrank Caruso 《Progress in Polymer Science》2012,37(7):985-1003
The synthesis of nanoengineered materials with precise control over material composition, architecture and functionality is integral to advances in diverse fields, including biomedicine. Over the last 10 years, click chemistry has emerged as a prominent and versatile approach to engineer materials with specific properties. Herein, we highlight the application of click chemistry for the synthesis of nanoengineered materials, ranging from ultrathin films to delivery systems such as polymersomes, dendrimers and capsules. In addition, we discuss the use of click chemistry for functionalizing such materials, focusing on modifications aimed at biomedical applications. 相似文献
93.
94.
Bingnan He Xia Wang Xini Jin Zimeng Xue Yinhua Ni Jianbo Zhu Caiyun Wang Yuanxiang Jin Zhengwei Fu 《Lipids》2020,55(3):251-260
Studies have elucidated that pyrethroids induce adipogenesis. It is also known that macrophages can affect the homeostasis of adipose tissue. However, whether and how the β-cypermethrin (β-CYP)-mediated inhibition of the macrophages affects adipogenesis remain unknown. To explore the effects of β-CYP on adipogenesis through modulating the function of macrophages, 3T3-L1 cells, a preadipocyte cell line, were exposed to culture medium from either RAW 264.7 cells, a macrophage cell line (RM), or β-CYP-treated RAW 264.7 cells (CRM). CRM decreased the inhibitory effects of RM treatment on cell proliferation and adipogenesis, as lipid accumulation, the CEBPA content, and Fasn and Acaca expression in 3T3-L1 cells were higher following CRM treatment than following RM treatment through the higher levels of the demethylated CEBPA promoter in 3T3-L1 cells. However, the medium from β-CYP- and N-acetyl-L-cysteine-cotreated RAW 264.7 cells (CNRM) partially restored the inhibitory effects of RAW 264.7 cells on 3T3-L1 cells that had been reduced by CRM, indicating that β-CYP might reduce the cytotoxicity and inhibitory effects of RAW 264.7 cells on the adipogenesis of 3T3-L1 cells through elevating ROS levels in RAW 264.7 cells. Moreover, exposure to β-CYP downregulated the TNF-α secretion in RAW 264.7 cells. In conclusion, these data demonstrated that β-CYP affected the function of RAW 264.7 cells, alleviating their inhibitory effects on adipogenesis and CEBPA demethylation in 3T3-L1 cells. β-CYP might achieve these effects through downregulating the secretion of TNF-α via elevating ROS levels in RAW 264.7 cells. Our experiments provide a new perspective on the obesogenic effect of pyrethroids. 相似文献
95.
Ponnusamy Nandha Kumar Shangavi Subramanian Uthirapathy Vijayalakshmi Sanjeevi Kannan 《Journal of the American Ceramic Society》2020,103(6):3528-3540
Structurally stable β-Ca3(PO4)2/t-ZrO2 composite mixtures with the aid of Dy3+ stabilizer were accomplished at 1500°C. The precursors comprising Ca2+, P5+, Zr4+, and Dy3+ have been varied to obtain five different combinations. The results revealed the fact that complete phase transformation of calcium-deficient apatite to β-Ca3(PO4)2 occurred only at 1300°C, whereas the evidence of t-ZrO2 crystallization is obvious at 900°C. The dual occupancy of Dy3+ at β-Ca3(PO4)2 and t-ZrO2 structures was evident; however, Dy3+ initially prefers to occupy β-Ca3(PO4)2 lattice until its saturation limit and thereafter accommodates at the lattice site of ZrO2. The typical absorption and emission behavior of Dy3+ were noticed in all the systems and, moreover, the surrounding symmetry of Dy3+ domains has been determined from the luminescence study. All the systems ensured paramagnetic response that is generally contributed by the presence of Dy3+. A gradual increment in the phase content of t-ZrO2 in the composite mixtures ensured a significant improvement in the hardness and Young's modulus of the investigated compositions. 相似文献
96.
Ximian Xiao Dr. Min Zhou Zihao Cong Jingcheng Zou Prof. Runhui Liu 《Chembiochem : a European journal of chemical biology》2023,24(3):e202200368
Peptide mimics, possessing excellent biocompatibility and protease stability, have attracted broad attention and research in the biomedical field. β-Peptides and β-peptoids, as two types of vital peptide mimics, have demonstrated great potential in the field of foldamers, antimicrobials and protein binding, etc. Currently, the main synthetic strategies for β-peptides and β-peptoids include solid-phase synthesis and polymerization. Among them, polymerization in one-pot can minimize the repeated separation and purification used in solid-phase synthesis, and has the advantages of high efficiency and low cost, and can synthesize β-peptides and β-peptoids with high molecular weight. This review summarizes the polymerization methods for β-peptides and β-peptoids. Moreover, future developments of the polymerization method for the synthesis of β-peptides and β-peptoids will be discussed. 相似文献
97.
《Ceramics International》2023,49(13):21246-21254
A glass with the composition 7.9 Li2O∙2.0 MgO∙1.4 ZnO∙10 Al2O3∙2.7 B2O3∙72.6 SiO2∙0.9 ZrO2∙2.1 TiO2∙0.4 Sb2O3 was thermally treated at temperatures in the range from 650 to 750 °C. During thermal treatment, at first, nearly spherical Zr1-xTixO4 crystals with sizes of 5–20 nm were formed. On these nanocrystals, elongated particles consisting of TiO2 were observed to grow. Subsequently hexagonal β-quartz solid solution was formed at temperatures ≥650 °C. In this β-quartz solid solution, Zn as well as Mg and excess Al were incorporated. At temperatures >690 °C, the formation of tetragonal β-spodumene solid solution was observed. In the microstructure of the formed glass-ceramics, a volume concentration of around 12% spherical aggregates with a diameter of 1.5–2 μm composed of β-spodumene solid solution and areas enriched in Al and Zn occur. These heterogenous structures were formed by the transformation of β-quartz solid solutions to β-spodumene solid solution. At the same time, Zn(Mg) and excess Al were expelled from the aluminosilicate phase and a cubic spinel type phase Zn(Mg)Al2O4 was formed. These aggregates did not contain a glassy phase. In-between these spherical aggregates, i.e. in around 88% of the volume, tiny Zr1-xTixO4 crystals, aluminosilicate crystals with diameters of around 200 nm, and a glass phase shoved away by these growing crystals consisting of oxides of Mg, Zn, Al, Si, and Sb happened to occur. 相似文献
98.
Ling Pan Pengju Chen Peng Xiao Ling He Wei Zhou Yang Li 《International Journal of Applied Ceramic Technology》2023,20(3):1740-1752
The mullite and ytterbium disilicate (β-Yb2Si2O7) powders as starting materials for the Yb2Si2O7/mullite/SiC tri-layer coating are synthesized by a sol–gel method. The effect of SiC whiskers on the anti-oxidation properties of Yb2Si2O7/mullite/SiC tri-layer coating for C/SiC composites in the air environment is deeply studied. Results show that the formation temperature and complete transition temperature of mullite were 800–1000 and 1300°C, respectively. Yb2SiO5, α-Yb2Si2O7, and β-Yb2Si2O7 were gradually formed between 800 and 1000°C, and Yb2SiO5 and α-Yb2Si2O7 were completely transformed into β-Yb2Si2O7 at a temperature above 1200°C. The weight loss of Yb2Si2O7/(SiCw–mullite)/SiC tri-layer coating coated specimens was 0.15 × 10−3 g cm−2 after 200 h oxidation at 1400°C, which is lower than that of Yb2Si2O7/mullite/SiC tri-layer coating (2.84 × 10−3 g cm−2). The SiC whiskers in mullite middle coating can not only alleviate the coefficient of thermal expansion difference between mullite middle coating and β-Yb2Si2O7 outer coating, but also improve the self-healing performance of the mullite middle coating owing to the self-healing aluminosilicate glass phase formed by the reaction between SiO2 (oxidation of SiC whiskers) and mullite particles. 相似文献
99.
Memory effect of locally ordered α-phase in the melting and phase transformation behavior of β-isotactic polypropylene 总被引:1,自引:0,他引:1
Kilwon Cho D Nabi SahebHoichang Yang Byoung-Il KangJoonkyung Kim Sang-Soo Lee 《Polymer》2003,44(14):4053-4059
Structural changes in β-isotactic polypropylene (β-iPP) during the heating were studied by means of differential scanning calorimetry and real-time in situ X-ray diffraction using a synchrotron source. Crystalline phase transformation and the memory effect caused by residual nuclei of α-iPP were observed during the heating of β-iPP. The memory effect observed in β-iPP during heating and crystallization is believed to be due to the existence of locally ordered α-from in the melt. The effect of local α-form order was probed by studying the behavior under heating of samples with a range of thermal histories. Samples were heated above the equilibrium melting temperature of iPP to remove all residual local order and the memory effect associated with this local order. The samples crystallized isothermally at different temperatures exhibited a significantly different melting and phase transformation behavior during heating. β-iPP is found to be an excellent material for the study of polymorphism, phase transformations, and characteristic memory effects in semicrystalline polymers. 相似文献
100.
An-Long Li 《Polymer》2004,45(19):6533-6537
The first example of living cationic random copolymerization of β-pinene and isobutylene was achieved with 1-phenylethyl chloride/TiCl4/Ti(OiPr)4/nBu4NCl (TiCl4/Ti(OiPr)4 mole ratio: 3/1) initiating system in CH2Cl2 at −40 °C. β-Pinene and isobutylene was consumed at almost the same rate, suggesting that the two monomers exhibit almost equal reactivity. At any monomer feed ratio, the number-average molecular weight (Mn) of the copolymers increased in direct proportion to the total monomer conversion, and the molecular weight distribution was relatively narrow (Mw/Mn=1.1-1.2) throughout the reaction. The reactivity ratios determined by the Kelen-Tüdõs method were rβ-pinene=1.1 and risobutylene=0.89, which indicated that the composition of copolymer is approximately identical to the monomer feed ratio. The analysis of the structure and sequence distribution of the copolymers by 1H NMR spectroscopy further confirmed that perfectly random copolymers were obtained by this living cationic polymerization system. The glass transition temperatures of the copolymers obtained with varying monomer compositions were also determined by DSC method. 相似文献