A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteins

A new, versatile, multiphasic buffer system for high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins in the relative molecular weight range of 300 000-3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above M(r) range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pK(a), as the buffering counterion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6-200 kDa M(r) range, with minimal difficulties in the post electrophoretic identification processes.     

Evaluation of liposomal delivery of antisense oligonucleotide by capillary electrophoresis with laser-induced fluorescence detection

Two widely used commercial cationic liposome formulations, Lipofectamine and Escort, were evaluated for drug delivery efficacy with capillary electrophoresis coupled with laser-induced fluorescence detection using a fluorescein conjugated 2'-O-methyl-phosphorothioate (Me-PS) antisense oligonucleotide and the HeLa cell line. Binding constants were estimated by monitoring changes in the electrophoretic mobility of the oligonucleotide with the liposome solution in the running buffer. From these changes in mobility, the binding constants for Lipofectamine and Escort liposomes with Me-PS oligomer were estimated to be 1139 and 590 M(-1), respectively. Additionally, intracellular concentrations and gene expression were quantified for the liposome formulations.     

Chain mechanisms for the dehydro-bromination of ring-substituted α-bromoacetophenones in alcohols

Ring substituted α-bromoacetophenones undergo efficient photodecomposition upon ultraviolet irradiation in alcohol solvents. The process involves chain reactions mediated by the ketyl radicals derived by hydrogen abstraction from the alcohols. It is suggested that two chain reactions involving hydrogen and electron transfer may be taking place concurrently. Competitive studies lead to relative rate constants for the reactions of ketyl radicals with ring-substituted α-bromoacetophenones.     

Stannane-free chemoselective hydrodehalogenation of 4-halotetrahydropyrans: scope and application to natural product synthesis

A stannane-free hydrodehalogenation of 4-halotetrahydropyran under very mild conditions has been developed. This methodology allows selective one-pot dehalogenation and/or debenzylation depending on the type of halide-substrate used. The applicability of this methodology is well demonstrated in the synthesis of a key intermediate toward the enantioselective synthesis of (+)-SCH 351448.     

Flow regimes and two-phase pressure gradient in horizontal straight tubes: Experimental results for HFO-1234yf, R-134a and R-410A

Two-phase flow regime visualizations of HFO-1234yf and R-134a in a 6.70 mm inner diameter glass straight tube have been simultaneous investigated by top and side views with a high speed high resolution camera. No major difference was observed between both refrigerants. HFO-1234yf flow regimes were satisfactorily predicted by the Wojtan et al. [1] flow pattern map. In addition, 819 pressure drop data points measured during two-phase flow of refrigerants HFO-1234yf, R-134a and R-410A in horizontal straight tubes are presented. The tube diameter (D) varies from 7.90 to 10.85 mm. The mass velocity ranges from 187 to 1702 kg m⁻² s⁻¹ and the saturation temperatures from 4.8 °C to 20.7 °C. The results are compared against 10 well-known two-phase frictional pressure drop prediction methods. For the entire database, the best accuracy is given by the method of Müller-Steinhagen and Heck [2] with around 90% of the data predicted within a ±30% error band. An analysis was carried out on the maximum pressure gradient and on the corresponding vapor quality. A statistical analysis for each flow regime was also carried out.