醌蛋白——猪肾二胺氧化酶的提取和性质

新鲜猪肾匀浆后，经热处理、盐析、羟基磷灰石和ＤＥＡＥ－纤维素柱层析等纯化步骤，二胺氧化酶的收得率为２３．９％，纯化倍数为４２５．该酶进行凝胶电泳后，经氨基黑、酶活性和ＮＢＴ溶液染色分别得到相对应的蛋白质、酶活性及醌辅基谱带．该酶可与腐胺、尸胺、己二胺、组胺等底物作用，释放出Ｈ２Ｏ２，当底物为腐胺时，最适浓度为５ｍｍｏｌＬ－１，Ｋｍ值为０．５ｍｍｏｌＬ－１，最适ｐＨ为７．０，最适温度为４０°Ｃ．在非酶系统中，该酶可与ＮＢＴ溶液反应，呈现紫色，并随时间延长而加深．经ＳＤＳ板状不连续聚丙烯酰胺凝胶电泳，得该酶亚基分子量为８．３×１０４．     

In Silico Structure-Guided Optimization and Molecular Simulation Studies of 3-Phenoxy-4-(3-trifluoromethylphenyl)pyridazines as Potent Phytoene Desaturase Inhibitors

A series of novel 3-phenoxy-4-(3-trifluoromethylphenyl)pyridazines 2–5 were designed, based on the structure of our previous lead compound 1 through the in silico structure-guided optimization approach. The results showed that some of these new compounds showed a good herbicidal activity at the rate of 750 g ai/ha by both pre- and post-emergence applications, especially compound 2a, which displayed a comparable pre-emergence herbicidal activity to diflufenican at 300–750 g ai/ha, and a higher post-emergence herbicidal activity than diflufenican at the rates of 300–750 g ai/ha. Additionally, 2a was safe to wheat by both pre- and post-emergence applications at 300 g ai/ha, showing the compound’s potential for weed control in wheat fields. Our molecular simulation studies revealed the important factors involved in the interaction between 2a and Synechococcus PDS. This work provided a lead compound for weed control in wheat fields.     

Structure–property relationship in PCL/starch blend compatibilized with starch‐g‐PCL copolymer

The polycaprolactone (PCL)/starch blends were prepared by using the starch‐g‐PCL (SGCL) graft copolymers as compatibilizers, and their mechanical properties were correlated with the compatibilizing effect of the SGCL copolymers having various molecular structures. The modulus and strength of the PCL/starch blend were decreased, whereas the percent elongation and the toughness were increased remarkably with the addition of SGCL having appropriate graft structure. These property changes were analyzed in terms of the PCL crystallinity and the interfacial adhesion between the PCL matrix and starch dispersion phases, which were dominated by the compatibilizing effects of the SGCL copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2430–2438, 1999     

A Novel Route to the Fused Maleic Anhydride Moiety of CP Molecules

A seven‐step cascade reaction —in which selective mesylation, epoxide formation, epoxide lysis, cyclization, reiterative oxidation, and nitrogen–oxygen exchange occur sequentially—facilitates the construction of the maleic anhydride moiety of CP molecules 1 and 2 (>93% yield per step). Unstable intermediates of this reaction sequence were detected, providing evidence for the proposed mechanism and resulting in the discovery of a new chemical entity.     

Tunable Oxygen Activation for Catalytic Organic Oxidation: Schottky Junction versus Plasmonic Effects

The charge state of the Pd surface is a critical parameter in terms of the ability of Pd nanocrystals to activate O₂ to generate a species that behaves like singlet O₂ both chemically and physically. Motivated by this finding, we designed a metal–semiconductor hybrid system in which Pd nanocrystals enclosed by {100} facets are deposited on TiO₂ supports. Driven by the Schottky junction, the TiO₂ supports can provide electrons for metal catalysts under illumination by appropriate light. Further examination by ultrafast spectroscopy revealed that the plasmonics of Pd may force a large number of electrons to undergo reverse migration from Pd to the conduction band of TiO₂ under strong illumination, thus lowering the electron density of the Pd surface as a side effect. We were therefore able to rationally tailor the charge state of the metal surface and thus modulate the function of Pd nanocrystals in O₂ activation and organic oxidation reactions by simply altering the intensity of light shed on Pd–TiO₂ hybrid structures.     

Mechanistic Insights into the Interface‐Directed Transformation of Thiols into Disulfides and Molecular Hydrogen by Visible‐Light Irradiation of Quantum Dots

Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible‐light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H₂ without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground‐state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants.     

Mechanically Interlocked Single‐Wall Carbon Nanotubes

Extensive research has been devoted to the chemical manipulation of carbon nanotubes. The attachment of molecular fragments through covalent‐bond formation produces kinetically stable products, but implies the saturation of some of the C? C double bonds of the nanotubes. Supramolecular modification maintains the structure of the SWNTs but yields labile species. Herein, we present a strategy for the synthesis of mechanically interlocked derivatives of SWNTs (MINTs). In the key rotaxane‐forming step, we employed macrocycle precursors equipped with two π‐extended tetrathiafulvalene SWNT recognition units and terminated with bisalkenes that were closed around the nanotubes through ring‐closing metathesis (RCM). The mechanically interlocked nature of the derivatives was probed by analytical, spectroscopic, and microscopic techniques, as well as by appropriate control experiments. Individual macrocycles were observed by HR STEM to circumscribe the nanotubes.     

Highly Enantioselective Construction of Tricyclic Derivatives by the Desymmetrization of Cyclohexadienones

The asymmetric synthesis of tricyclic compounds by the desymmetrization of cyclohexadienones is presented. The reaction tolerated a large variety of substituents at different positions of the cyclohexadienone, and heterocyclic rings of different sizes were accessible. Density functional theory calculations showed that the reaction proceeds through an asynchronous [4+2] cycloaddition.     

Optical Control of Acetylcholinesterase with a Tacrine Switch

Photochromic ligands have been used to control a variety of biological functions, especially in neural systems. Recently, much effort has been invested in the photocontrol of ion channels and G‐protein coupled receptors found in the synapse. Herein, we describe the expansion of our photopharmacological approach toward the remote control of an enzyme. Building on hallmark studies dating from the late 1960s, we evaluated photochromic inhibitors of one of the most important enzymes in synaptic transmission, acetylcholinesterase (AChE). Using structure‐based design, we synthesized several azobenzene analogues of the well‐known AChE inhibitor tacrine (THA) and determined their effects on enzymatic activity. One of our compounds, AzoTHA, is a reversible photochromic blocker of AChE in vitro and ex vivo with high affinity and fast kinetics. As such, AzoTHA can be used to control synaptic transmission on the neuromuscular endplate based on the light‐dependent clearance of a neurotransmitter.