聚苯胺光诱导激子和极化子的动力学研究

此文研究了三种不同分子结构的聚苯胺（本征态聚苯胺，间位聚苯胺和掺入有机玻璃的掺杂态聚苯胺）的飞秒非线性光学响应过程。用飞秒时间分辨吸收光谱技术测量了三种样品的激子和极化子的光激发和弛豫过程。从一个三能级模型出发，分析了上述过程的来源。最后讨论了存在于聚苯胺中的这种超快驰豫过程在光学双稳器件中的应用     

Design and synthesis of a tribranched phenylethynyl‐terminated aryl ether compound and its use as a reactive diluent for PETI‐5

In this study, a tribranched, phenylethynyl‐terminated aryl ether compound (Tri‐PE‐PAEK) was synthesized. This novel star‐shaped compound exhibits a good combination of properties, such as a low melting temperature (252 °C) and good solubility in aprotic solvents, as well as a low melt viscosity (0.1 P at 280 °C). All these advantages make it a good candidate material for modern processing techniques such as resin infusion and resin transfer molding, which are the most favorable methodologies for current economical manufacturing of polymer matrix/carbon fiber composites. Furthermore, after undergoing thermal curing to yield a network at 370 °C for 1 h, a cured sample exhibited an unexpectedly higher glass transition temperature (370 °C), storage modulus retention above the glass transition temperature, and good thermal stability. In addition, this compound can be used as a reactive diluent for phenylethynyl‐terminated imide oligomer, which has the molecular weight of 5000 g/mol (PETI‐5) to reduce its viscosity and lower the minimum temperature of the minimum viscosity. Meanwhile, the toughness of a cured blended resin can be greatly increased with the addition of just 10% Tri‐PE‐PAEK to PETI‐5. Further loading levels of Tri‐PE‐PAEK in the blending would lead to a higher storage modulus and a higher mechanical strength without compromising the thermal stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4844–4854, 2007     

Commercial Fe- or Co-containing carbon nanotubes as catalysts for NH3 decomposition

Fresh commercial carbon nanotubes (CNTs) containing residual Co or Fe nanoparticles are highly active for NH3 decomposition while the microstructure of CNTs remains unchanged. The catalysts are promising for elimination of NH3 from coal gasification stream and for production of H2 from NH3.     

Simultaneous arming and structure/activity studies of natural products employing O-H insertions: an expedient and versatile strategy for natural products-based chemical genetics

The identification of "druggable" targets is an immediate opportunity and challenge in the post-genomic era. Natural products are enduring tools for basic cellular studies and leads for identifying medically relevant protein targets. However, their use for these studies is often hampered by limited quantities and a lack of selective and mild monofunctionalization reactions. The development of selective methods that could simultaneously equip the natural product with a reactive group for subsequent conjugation to reporter tags and provide important structure-activity relationship (SAR) information, requiring only a knowledge of functional groups present in the natural product, could significantly decrease the time between bioactive natural product isolation and target identification. Herein, we report such a strategy that enables simultaneous arming and SAR studies of alcohol-containing natural products involving both chemo- and site-selective ("chemosite" selective) and site-nonselective O-H insertion reactions with rhodium carbenoids derived from alkynyl diazo acetates. This strategy was applied to a diverse set of natural products, and general guidelines for predicting chemosite selectivity were formulated. A subsequent Sharpless-Hüisgen [3 + 2] cycloaddition reaction with the appended alkyne allows for attachment of a variety of reporter tags. Using this strategy, we synthesized a novel FK506-biotin conjugate that enabled pull-down of the entire "immunosuppressive complex" including FKBP12, calcineurins A and B, and calmodulin. In addition, the potential for a chemoselective but site-nonselective process was shown with both gibberellic acid methyl ester and brefeldin A using only achiral rhodium catalysts.     

Structure-guided design of AMP mimics that inhibit fructose-1,6-bisphosphatase with high affinity and specificity

AMP binding sites are commonly used by nature for allosteric regulation of enzymes controlling the production and metabolism of carbohydrates and lipids. Since many of these enzymes represent potential drug targets for metabolic diseases, efforts were initiated to discover AMP mimics that bind to AMP-binding sites with high affinity and high enzyme specificity. Herein we report the structure-guided design of potent fructose 1,6-bisphosphatase (FBPase) inhibitors that interact with the AMP binding site on FBPase despite their structural dissimilarity to AMP. Molecular modeling, free-energy perturbation calculations, X-ray crystallography, and enzyme kinetic data guided our redesign of AMP, which began by replacing the 5'-phosphate with a phosphonic acid attached to C8 of the adenine base via a 3-atom spacer. Additional binding affinity was gained by replacing the ribose with an alkyl group that formed van der Waals interactions with a hydrophobic region within the AMP binding site and by replacing the purine nitrogens N1 and N3 with carbons to minimize desolvation energy expenditures. The resulting benzimidazole phosphonic acid, 16, inhibited human FBPase (IC50 = 90 nM) 11-fold more potently than AMP and exhibited high specificity for the AMP binding site on FBPase. 16 also inhibited FBPase in primary rat hepatocytes and correspondingly resulted in concentration-dependent inhibition of the gluconeogenesis pathway. Accordingly, these results suggest that the AMP site of FBPase may represent a potential drug target for reducing the excessive glucose produced by the gluconeogenesis pathway in patients with type 2 diabetes.     

Synthesis of 1,3,5-tricarbonyl derivatives by condensation of 1,3-bis(silyl enol ethers) with acid chlorides

A variety of 1,3,5-tricarbonyl derivatives were prepared by reaction of 1,3-bis(silyl enol ethers) with acid chlorides under mild conditions. This includes reactions of both aromatic and aliphatic acid chlorides and bis(acid chlorides). The yields vary depending on the type of acid chloride employed.