Design and Synthesis of (2-oxo-1,2-Dihydroquinolin-4-yl)-1,2,3-triazole Derivatives via Click Reaction: Potential Apoptotic Antiproliferative Agents

A mild and versatile method based on Cu-catalyzed [2+3] cycloaddition (Huisgen-Meldal-Sharpless reaction) was developed to tether 3,3’-((4-(prop-2-yn-1-yloxy)phenyl)methylene)bis(4-hydroxyquinolin-2(1H)-ones) with 4-azido-2-quinolones in good yields. This methodology allowed attaching three quinolone molecules via a triazole linker with the proposed mechanism. The products are interesting precursors for their anti-proliferative activity. Compound 8g was the most active one, achieving IC₅₀ = 1.2 ± 0.2 µM and 1.4 ± 0.2 µM against MCF-7 and Panc-1 cell lines, respectively. Moreover, cell cycle analysis of cells MCF-7 treated with 8g showed cell cycle arrest at the G2/M phase (supported by Caspase-3,8,9, Cytochrome C, BAX, and Bcl-2 studies). Additionally, significant pro-apoptotic activity is indicated by annexin V-FITC staining.     

Effect of γ-irradiation on slow crack growth in a copolymer of polyethylene

The effect of γ-irradiation on slow crack growth (SCG) in a medium density polyethylene (MDPE) was measured and compared with behavior of high density polyethylene (HDPE) and a recrystallized HDPE (RCHDPE). The three materials exhibited the same dependence on dose up to 3 Mrd. The HDPE became brittle above 50 Mrd. The resistance to SCG of MDPE and RCHDPE increased very rapidly with dose above 3 Mrd, until at 50–80 Mrd their resistance to SCG became extraordinarily high. This high resistance to SCG was accompanied by a transition from crazing to shear deformation at the root of a notch. It was found that for the same concentration, crosslinks are more effective than short chain branches for increasing resistance to SCG. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2349–2354, 1998     

Models for the Carbonyl–ene Cyclization Reaction: Open and Closed Transition States

Different cyclization products are formed with different Lewis acids in the ene cyclization of 5-hexenals (see scheme on the right; a: methylaluminum bisphenoxide, b: Me₂AlCl, c: Sc(OSO₂CF₃)₃). This is not surprising, but it is gratifying that these result can be rationalized with an internally consistent model.     

Dynamic light scattering of poly(n-laurylmethacrylate) in the melt and in concentrated ethyl acetate solutions

Dynamic light-scattering measurements have been made on the “soft” polymer: poly(n-laurylmethacrylate) (PLMA) in solution in ethyl acetate over the concentration range 0.1 < C < 0.9 g/mL as well as melt PLMA. With the concentrated solutions, the hydrodynamic screening length (ξ_h) scales with an exponent of −0.7 below C ≈ 0.3 g/mL. Importantly, ξ_h decreases above 0.3 g/mL, and the concentration dependence increases strongly above this concentration. The latter contrasts with the behavior in a variety of well-studied poly(styrene) solutions, which are inevitably investigated close to the glass point, and for which there is a pronounced increase of ξ_h over the same concentration range. In PLMA solutions, the decrease in ξ_h parallels the behavior of the static screening length (ξ_s) which has been observed in other flexible polymer systems. Dynamic “clusters” (also termed “long-range density fluctuations”) contribute a large part of the scattered intensity above the concentration 0.6 g/mL and also in melt PLMA which contrasts with poly(styrene) systems in which they are absent. In common with the clusters recently observed in another polymeric melt, poly(methyl-p-tolylsiloxane) (ref. 9) this component is diffusive. While, however, in the latter system the clusters “melt out” at 90°C, we find in the well-matured PLMA systems that the cluster amplitude is temperature-independent (within the temperature-time range studied) in the solutions up to at least 80°C and up to at least 150°C in the melt, which were the highest temperatures examined. The clusters in the PLMA systems have a correlation length of the magnitude 65 nm in the melt, whereas in the solutions this dimension varies between 73 nm at 0.9 g/mL to 126 nm at 0.7 g/mL. In PLMA the clusters are presumed to arise from local segregation owing to the large paraffinic side groups on the chain. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1013–1024, 1997