One-pot synthesis of luotonin A and its analogues

Starting with inexpensive reagents, a self-directed chemical process with the aid of a single metal triflate was readily achieved to concomitantly construct quinazoline and pyrroloquinoline cores to afford the synthesis of luotonin A and its analogues. Among all compounds prepared, 2c, 2d, and 3b exhibit more potent inhibitory activity than luotonin A against human topoisomerase I.     

A new micropatterning method of soft substrates reveals that different tumorigenic signals can promote or reduce cell contraction levels

In tissues, cell microenvironment geometry and mechanics strongly impact on cell physiology. Surface micropatterning allows the control of geometry while deformable substrates of tunable stiffness are well suited for the control of the mechanics. We developed a new method to micropattern extracellular matrix proteins on poly-acrylamide gels in order to simultaneously control cell geometry and mechanics. Microenvironment geometry and mechanics impinge on cell functions by regulating the development of intra-cellular forces. We measured these forces in micropatterned cells. Micropattern geometry was streamlined to orient forces and place cells in comparable conditions. Thereby force measurement method could be simplified and applied to large-scale experiment on chip. We applied this method to mammary epithelial cells with traction force measurements in various conditions to mimic tumoral transformation. We found that, contrary to the current view, all transformation phenotypes were not always associated to an increased level of cell contractility.     

A copper(II) complex as an intermediate of copper(I)-catalyzed C-N cross coupling of N-phenylaniline with aryl halide by in situ ESI-MS study

Complexes [Cu(NPh(2))(2)](-), [Cu(NPh(2))I](-) and K[Cu(phen)(NPh(2)) (p-tolyl)](+) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the copper(I)-catalyzed C-N coupling reaction under the catalytic reaction condition indicating that they are intermediates in the reaction. A catalytic cycle composed of a free radical path and a 2e oxidative addition path is proposed based on these observations.     

Intermediates of copper(I)-catalyzed C-S cross coupling of thiophenol with aryl halide by in situ ESI-MS study

Complexes [Cu(SPh)(2)](-), [Cu(SPh)I](-) and K[Cu(SPh)(2)(Ph)](+) were observed by in situ electrospray ionization mass spectrometry (ESI-MS) analysis of the copper(i)-catalyzed C-S coupling reaction under catalytic reaction conditions indicating that they are intermediates in the reaction. A catalytic cycle was proposed based on these observations.     

Development of novel 3D-QSAR combination approach for screening and optimizing B-Raf inhibitors in silico

B-Raf is a member of the RAF family of serine/threonine kinases: it mediates cell division, differentiation, and apoptosis signals through the RAS-RAF-MAPK pathway. Thus, B-Raf is of keen interest in cancer therapy, such as melanoma. In this study, we propose the first combination approach to integrate the pharmacophore (PhModel), CoMFA, and CoMSIA models for B-Raf, and this approach could be used for screening and optimizing potential B-Raf inhibitors in silico. Ten PhModels were generated based on the HypoGen BEST algorithm with the flexible fit method and diverse inhibitor structures. Each PhModel was designated to the alignment rule and screening interface for CoMFA and CoMSIA models. Therefore, CoMFA and CoMSIA models could align and recognize diverse inhibitor structures. We used two quality validation methods to test the predication accuracy of these combination models. In the previously proposed combination approaches, they have a common factor in that the number of training set inhibitors is greater than that of testing set inhibitors. In our study, the 189 known diverse series B-Raf inhibitors, which are 7-fold the number of training set inhibitors, were used as a testing set in the partial least-squares validation. The best validation results were made by the CoMFA09 and CoMSIA09 models based on the Hypo09 alignment model. The predictive r(2)(pred) values of 0.56 and 0.56 were derived from the CoMFA09 and CoMSIA09 models, respectively. The CoMFA09 and CoMSIA09 models also had a satisfied predication accuracy of 77.78% and 80%, and the goodness of hit test score of 0.675 and 0.699, respectively. These results indicate that our combination approach could effectively identify diverse B-Raf inhibitors and predict the activity.     

Pore-spanning lipid membrane under indentation by a probe tip: a molecular dynamics simulation study

We study the indentation of a free-standing lipid membrane suspended over a nanopore on a hydrophobic substrate by means of molecular dynamics simulations. We find that in the course of indentation the membrane bends at the point of contact and the fringes of the membrane glide downward intermittently along the pore edges and stop gliding when the fringes reach the edge bottoms. The bending continues afterward, and the large strain eventually induces a phase transition in the membrane, transformed from a bilayered structure to an interdigitated structure. The membrane is finally ruptured when the indentation goes deep enough. Several local physical quantities in the pore regions are calculated, which include the tilt angle of lipid molecules, the nematic order, the included angle, and the distance between neighboring lipids. The variations of these quantities reveal many detailed, not-yet-specified local structural transitions of lipid molecules under indentation. The force-indentation curve is also studied and discussed. The results make a connection between the microscopic structure and the macroscopic properties and provide deep insight into the understanding of the stability of a lipid membrane spanning over nanopore.     

Effect of hydrophobicity of monomers on the structures and properties of 1,3:2,4-dibenzylidene-D-sorbitol organogels and polymers prepared by templating the gels

The effects of hydrophobicity of monomers on the structures and properties of 1,3:2,4-dibenzylidene-D-sorbitol (DBS) organogels and nanostructured polymers prepared by templating the self-assembled organogels were investigated in this study. Hydrophobic styrene (St), hydrophilic methyl (methacrylate) (MMA), and their mixtures were chosen as the monomers. Though the gelation time varied, the average diameters (around 10 nm) of DBS nanofibrils found in the resulting organogels did not change significantly, for monomers of different hydrophobicity, as observed by transmission electron microscopy (TEM). Nonetheless, new structures, DBS microaggregates, appeared when the MMA content in the monomers was high enough. These irregular, micrometer-sized DBS structures (microaggregates) may have formed because the aggregated DBS molecules were influenced by the MMA monomers, due to the hydrogen bonding between DBS and MMA. This was confirmed by Fourier transform infrared (FTIR) spectroscopy and could also explain the differences in the gelation time of the DBS organogels: gels form more slowly in MMA than in St because of the competing interaction, hydrogen bonding, between DBS and MMA. Subsequently, we thermally initiated the free-radical polymerization of these St/MMA co-monomers. PS/PMMA copolymers were obtained, and no macroscopic phase separation occurred after the polymerization. Finally, the porous structures of the polymers produced by the solvent extraction of the DBS templates were observed, using TEM.     

Electrophoresis of an arbitrarily oriented toroid in an unbounded electrolyte solution

The electrophoresis of a non-conducting rigid toroid in an unbounded Newtonian electrolyte solution having an arbitrary orientation is modeled theoretically under the condition of low surface potential. In particular, the influence of the orientation angle, defined as the angle between the applied electric field and the center line of the toroid, on its electrophoretic behavior as the thickness of double layer varies is investigated. The results of numerical simulation reveal that both the thickness of double layer and the orientation angle can influence appreciably the mobility of the toroid. In general, for a fixed orientation, the mobility of the toroid increases with decreasing double layer thickness, and for a fixed double layer thickness, the scaled electrophoresis mobility increases with increasing orientation angle. If the double layer is infinitely thin, then the present result reduces to that predicted by Smoluchowski, that is, the scaled electrophoretic mobility of the toroid is unity, and is not influenced by its shape. On the other hand, if it is infinitely thick, then the present result follows the same trend as that predicted by Henry, that is, the electrophoretic mobility of the toroid depends highly on its form effect, and the thicker the double layer the smaller that mobility. If the thickness of double layer is comparable to the radius of a toroid, the variation in the orientation angle can lead to as much as 40% difference in the mobility.     

Synthesis of the phenanthrene and cyclohepta[a]naphthalene skeletons via gold(I)-catalyzed intramolecular cyclization of unactivated cyclic 5-(2-arylethyl)-1,3-dienes

The gold(I)-catalyzed hydroarylation of cyclohexa-1,3-dienes bearing an aryl group and a gem-diester in the tether proceeds in a 1,4-addition manner and in a diastereoselective fashion to afford perhydrophenanthrene rings. The reaction proceeded via attack of the aryl group onto the gold-activated cyclic dienes followed by rearomatization and protodeauration to generate perhydrophenanthrenes in good yields. This hydroarylation can be applied to the synthesis of perhydrocyclohepta[a]naphthalenes from aryl-tethered cycloheptadienes and the gold(I) catalyst.     

Copper(I)-anilide complex [Na(phen)3][Cu(NPh2)2]: an intermediate in the copper-catalyzed N-arylation of N-phenylaniline

Complex [Na(phen)₃][Cu(NPh₂)₂] ( 2 ), containing a linear bis(N‐phenylanilide)copper(I) anion and a distorted octahedral tris(1,10‐phenanthroline)sodium counter cation, has been isolated from the catalytic C? N cross‐coupling reaction with the CuI/phen/tBuONa (phen=1,10‐phenanthroline) catalytic system. Complex 2 can react with 4‐iodotoluene to produce 4‐methyl‐N,N‐diphenylaniline ( 3 a ) with 70.6 % yield. In addition, 2 can work as an effective catalyst for C? N coupling under the same reaction conditions, thus indicating that 2 is the intermediate of the catalytic system. Both [Cu(NPh₂)₂]^? and [Cu(NPh₂)I]^? have been observed by in situ electron ionization mass spectrometry (ESI‐MS) under catalytic reaction conditions, thus confirming that they are intermediates in the reaction. A catalytic cycle has been proposed based on these observations. The molecular structure of 2 has been determined by single‐crystal X‐ray diffraction analysis.