生物催化在绿色化学和新药开发中的应用

近年来生物技术领域有了突破性进展，如: 公共基因数据库(GenBank)和蛋白质数据库(PDB)中序列的指数增长，高效基因克隆和表达平台的建立，可有效改进生物催化剂专一性、选择性和稳定性的酶定向进化技术的应用。这些进展使生物催化在化学合成中日趋重要[1]。本文综述了生物催化在如下领域的成功应用：在药物生产中用于开发经济的化学酶法合成工艺，在绿色化学领域中最大程度的减少废物的产生和危险试剂的应用，在天然化学领域中对天然产物进行修饰以发现具有更好生物活性的新药物。     

Syntheses and Studies of PEG-b-PNIPA Block Polymers

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Total synthesis of (−)-penicimutanin a and related congeners

The first total synthesis of penicimutanin A (1) was achieved within 10 steps (LLS). Key innovations in this synthesis consist of (1) a highly efficient electro-oxidative dearomatization; (2) an unprecedented bisoxirane-directed intermolecular aldol reaction from the sterically hindered face of the ketone and (3) the diastereoselective one-step Meerwein–Eschenmoser–Claisen rearrangement enabling the construction of vicinal quaternary stereocenters. Related family members e.g. penicimutanolone (3) and penicimutatin (5) have also been synthesized alongside, elucidating their absolute configurations, hence the absolute configuration of 1.

The first total synthesis of penicimutanin A (1) was achieved within 10 steps (LLS).     

Self-assembly, optical behavior, and permeability of a novel capsule based on an azo dye and polyelectrolytes

A novel capsule composed of an azo dye, Congo red (CR), and different polymers, including poly(styrenesulfonate, sodium salt) (PSS), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA), have been successfully fabricated by the layer-by-layer self-assembly technique. The stepwise linear deposition process was monitored by means of UV-visible absorption measurements. The formation of hollow capsules was verified by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). The resulting hollow PSS/PAH/CR/PDDA capsules displayed a sensitive response to visible light. Optical changes of the hollow capsules prior to and after the photoreaction were investigated in detail by means of UV-visible spectroscopy, CLSM, and SFM. It was found that the photochemical reaction of the assembled hollow capsules depends strongly on the matrix. Qualitative results on the permeability of the hollow capsule walls with CR as one component indicate that the permeability of the walls can be easily photo-controlled at varying irradiation time intervals without addition of external chemicals.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

ZrxTixAl1-2xO2的制备及其在三效催化剂上的应用

Zr_0.5Ti_0.5O₂(ZT) and Zr_0.25Ti_0.25Al_0.5O₂(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption， XRD and NH₃-TPD. The activity of Pt/Zr_0.5Ti_0.5O₂ and Pt/ Zr_0.5Ti_0.5Al_0.5O₂ catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area， larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon， carbon monoxide and nitrogen oxides， especially better conversion for nitrogen oxides (NO_x). The addition of Al₂O₃ into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural， structural， surface acidity and thermal stability.     

纳米镍-铁合金/膨胀石墨复合材料的制备、表征及其电磁屏蔽性能

The composites with nano-particles of Ni-Fe alloys dispersed on the nano-layers of expanded graphite (EG) were prepared by the impregnation of EG with ethanol solutions of nickel and iron acetates， followed by drying and reduction in H₂. The square nano-particles of Ni-Fe alloys with particle sizes of mainly 20～40 nm were found to be well spread on the layers of EG. The alloy nano-particles exhibited high shielding effectiveness (SE) for electromagnetic radiations at low frequencies due to their high magnetic conductivity. Since EG is electronically conductive and displayed high SE at high frequencies， the composites exhibited good SE at wide range of frequencies. The electric and magnetic conductivities of the composites could be monitored through regulating the loadings of alloy nano-particles on EG， and it was found that the composites with 20%～40% of the alloys exhibited good SE. Specifically， the composite 27%Ni-3%Fe-EG showed the excellent SE from 66 to 110 dB at the frequencies from 300 kHz to 1.5 GHz.     

Catalytic asymmetric synthesis of quaternary trifluoromethyl α- to ε-amino acid derivatives via umpolung allylation/2-aza-Cope rearrangement

In this study, we developed an efficient Ir-catalyzed cascade umpolung allylation/2-aza-Cope rearrangement of tertiary α-trifluoromethyl α-amino acid derivatives for the preparation of a variety of quaternary α-trifluoromethyl α-amino acids in high yields with excellent enantioselectivities. The umpolung reactivity empowered by the activation of the key isatin-ketoimine moiety obviates the intractable enantioselectivity control in Pd-catalyzed asymmetric linear α-allylation. In combination with quasi parallel kinetic resolution or kinetic resolution, the generality of this method is further demonstrated by the first preparation of enantioenriched quaternary trifluoromethyl β-, γ-, δ- and ε-amino acid derivatives.

In this study, we developed an efficient Ir-catalyzed cascade umpolung allylation/2-aza-Cope rearrangement for the preparation of a variety of quaternary trifluoromethyl α-ε-amino acids in high yields with excellent enantioselectivities.     

Aromatization of methane over different Mo-supported catalysts in the absence of oxygen

Both acidity and structure of the support are important factors in converting methane to aromatics. Lower SiO₂/Al₂O₃ ratio seems to favor the aromatization of methane over the Mo/HZSM-5 catalyst. When Pt is added as a modifier the activity of Mo/HZSM-5 catalyst will decrease slightly, but coke formation will enhanced.     

微量元素锌与小儿健康状况分析

对98例西安阎良一四一医院儿科门诊就诊的小儿发锌进行了测定，分析了锌与小儿健康的关系，并对低锌的小儿进行了治疗。通过治疗(药疗、食疗)症状明显好转，复查发锌正常者达85．7％。