The interplay between chemistry and biology in the design of enzymatic catalysts

Chemists and biologists are focusing considerable effort on the development of efficient, highly selective catalysts for the synthesis or modification of complex molecules. Two approaches are described here, the generation of catalytic antibodies and hybrid enzymes, which exploit the binding and catalytic machinery of nature in catalyst design. Characterization of these systems is providing additional insight into the mechanisms of molecular recognition and catalysis which may, in turn, lead to the design of tailor-made catalysts for applications in chemistry, biology, and medicine.     

Supramolecular Materials: Self-Organized Nanostructures

Miniaturized triblock copolymers have been found to self-assemble into nanostructures that are highly regular in size and shape. Mushroom-shaped supramolecular structures of about 200 kilodaltons form by crystallization of the chemically identical blocks and self-organize into films containing 100 or more layers stacked in a polar arrangement. The polar supramolecular material exhibits spontaneous second-harmonic generation from infrared to green photons and has an adhesive tape-like character with nonadhesive-hydrophobic and hydrophilic-sticky opposite surfaces. The films also have reasonable shear strength and adhere tenaciously to glass surfaces on one side only. The regular and finite size of the supramolecular units is believed to be mediated by repulsive forces among some of the segments in the triblock molecules. A large diversity of multifunctional materials could be formed from regular supramolecular units weighing hundreds of kilodaltons.     

Transition metal speciation in the cell: insights from the chemistry of metal ion receptors

The essential transition metal ions are avidly accumulated by cells, yet they have two faces: They are put to use as required cofactors, but they also can catalyze cytotoxic reactions. Several families of proteins are emerging that control the activity of intracellular metal ions and help confine them to vital roles. These include integral transmembrane transporters, metalloregulatory sensors, and diffusible cytoplasmic metallochaperone proteins that protect and guide metal ions to targets. It is becoming clear that many of these proteins use atypical coordination chemistry to accomplish their unique goals. The different coordination numbers, types of coordinating residues, and solvent accessibilities of these sites are providing insight into the inorganic chemistry of the cytoplasm.     

儿茶素的药理作用研究综述

目的研究表儿茶素(EC)对小鼠急性肺损伤(ALI)炎症反应的调节作用。方法采用吸入式气管滴注法在BALB/c小鼠中建立ALI模型,H8LE染色观察肺组织病理学变化,并结合基于超高效液相色谱与四极杆—飞行时间质谱联用技术(HILIC UHPLC-Q-TOF MS)的非靶向代谢组学方法对小鼠肺组织进行研究。结果对比空白对照组,LPS处理后的小鼠肺组织发生严重的炎症变化,而EC预处理组炎症现象比LPS组轻。经肺组织代谢轮廓分析发现：二十羟基花生四烯酸、色氨酸、苯丙氨酸、酪氨酸、ATP、磷酸胆碱、二十碳四烯酸、磷酸、烯醇和二磷酸葡萄糖等差异物与小鼠急性肺损伤内源性代谢密切相关,且涉及甘油酯代谢、糖酵解、甘油磷脂代谢、苯丙氨酸、酪氨酸和色氨酸生物合成、抗坏血酸代谢和胆碱代谢等6条代谢路径。结论运用代谢组学方法探讨了EC干预小鼠ALI的差异代谢物变化情况,为表儿茶素抗炎特性的研究提供了理论依据。     

Gulf stream cold-core rings: their physics, chemistry, and biology

Cyclonic Gulf Stream rings are energetic eddies in the warm Sargasso Sea consisting of a ring of Gulf Stream water surrounding a core of cold Slope Water. Initially a ring core has the characteristics of the Slope Water; it is rich in plants, animals, and nutrients. As a ring decays the Slope Water properties of its core are gradually replaced by those of the Sargasso Sea, where standing crops of plants, animals, and nutrients generally are low. Although the decay rate suggests a rather long lifetime (2 to 4 years), the usual death of a ring comes when it rejoins the Gulf Stream after 6 to 12 months.     

Batrachotoxin: chemistry and pharmacology

Batrachotoxin has been shown to be a pyrrolecarboxylic ester of a novel steroidal base with unique and selective actions on a variety of electrogenic membranes. The effects of batrachotoxin in neuromuscular preparations both pre- and postsynaptically, in nerve axons, in superior cervical ganglion, in heart Purkinje fibers, and in brain slices appear to be due to the selective and irreversible increase in permeability of membranes to sodium ions. The subsequent effects of this increase in Na(+) permeability evoked by batrachotoxin-such as membrane depolarization, enhanced spontaneous transmitter release, muscle contracture, and enhanced formation of cyclic AMP in brain slices-may be blocked reversibly by tetrodotoxin.     

Structure and Properties of Crystalline Polymers: Supramolecular structure is complex, can be controlled, and influences mechanical properties

Through control of the crystallization process many polymers can be made to exhibit a broad spectrum of structural possibilities, ranging from a state of high disorder to one of high order. Emphasis has been placed on bulk-crystallized polymers which normally fall near the center of this spectrum. This was done in part because polymers are most commonly fabricated in this manner, and also because the amount of attention given in recent years to crystals grown from dilute solution has tended to obscure important aspects of the structure of bulk-crystallized polymers. Differences in the structure of the interlamellar regions account most reasonably for many of the variations in mechanical properties that crystalline polymers can be made to display. The interlamellar amorphous model, proposed here as a structural model for bulk-crystallized polymers, largely neglects the lamellae themselves, because so little is known about the structure of the lamellae of bulk-crystallized polymers and how variations in lamellar structure can affect properties. This model is intended, therefore, as both a working hypothesis to aid further investigation and as an outline to be filled in as more is learned about the supramolecular structure of crystalline polymers (31).