On the efficiency of methylene blue versus persulfate catalysis of polyacrylamide gels, as investigated by capillary zone electrophoresis

Abstract

The efficiency of a novel method of photopolymerization, based on photoinitiating the reaction with methylene blue (MB), in presence of a redox couple (sodium toluenesulfinate and diphenyliodonium chloride), vs, the conventional persulfate--N,N,N',N'-tetramethylethylenediamine redox couple was investigated as a function of different effectors in solution. Oxygen dissolved in the gelling mixture strongly quenches persulfate catalysis, while leaving essentially unaltered the process initiated by photopolymerization. On the contrary, the presence of 8 M urea substantially accelerates a persulfate-driven reaction, boosting the conversion of monomers to near completion (> 98%) while leaving the photopolymerization process largely unaffected. Polyacrylamide polymerization has also been performed in a number of hydroorganic solvents (all in a 50:50 v/v ratio): dimethyl sulfoxide (DMSO), tetramethylurea, formamide and dimethylformamide. In all cases, the persulfate-catalyzed reaction was strongly quenched and even completely inhibited (in DMSO), whereas the photopolymerization process was essentially unaffected by any of these organic solvents. The reaction kinetics of the methylene blue-driven reaction could not be ameliorated when admixing an anionic dye (e.g., eosin Y) to the cationic MB, even when amply changing their molar ratios. Thus, it appears that photocatalysis with MB (and the redox couple sodium toluene-sulfinate and diphenyliodonium chloride) is a unique process, proceeding at optimum rate under the most adverse conditions, completely insensitive to any kind of positive and negative effectors and able to ensure at least 95% monomer conversion under the standard conditions of 1 h reaction time at room temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial and temporal depletion of ions from noncrosslinked denaturing polyacrylamide in capillary electrophoresis

“…[27] also noticed a change in the properties of polyacrylamide in time, They found that the velocity of DNA changes if the gel is not aged before used. Caglio and Righetti [29] studied the polymerization kinetics of polyacrylamide and reported that the polymerization is finished within 1 day.…”

Prevention of artifactual protein oxidation generated during sodium dodecyl sulfate‐gel electrophoresis

“…This system is used to polymerize SDS gels under nonoxidizing conditions, and the electrophoretic resolution of the gel polymerized with this system is similar to gels polymerized with the APS/TEMED system [6]. An alternative that permits the addition of various cosolvents uses methylene blue as the photoinitiator [33]. Before photopolymerization, the acrylamide mixtures were degassed for 30 min.…”

Gel polymerization in detergents: Conversion efficiency of methylene blue vs. persulfate catalysis, as investigated by capillary zone electrophoresis

“…Thus, it is difficult to decide at present if this strong inhibition is simply due to subtraction of catalyst from the reacting mixture (broadly speaking, this is also an inhibition process) or to stronger partitioning of acrylamide into the micelle. The most striking observation, though, as already reported in the case of hydroorganic solvents [7], is the total lack of sensitivity of methylene blue to inhibition by any of the tested detergents. The reaction proceeds at the very same rate as control gels and always achieves remarkable conversion (in all cases > 95%) at the end of the standard 60 min period at room temperature.…”

“…Thus, any mechanism disrupting such monomer "strings" should unavoidably slow down or hamper chain growth. We had in fact already reported inhibition of radical polymerization in hydroorganic mixtures [7], which also act as chaotropes.…”

“…In the last article of this series [7], the efficiency of MB-vs. persulfate-driven catalysis was assessed in a series of hydroorganic solvents (all in a 50°/o:50~/' v/v ratio): dimethylsulfoxide, tetramethylurea, formamide and dimethyl formamide, reported as useful disaggregating agents in a number of articles dealing with RNA and DNA separations (see [8] for a review). In all cases, the persulfate-catalyzed reaction was strongly quenched and even completely inhibited, whereas photopolymerization was essentially unaffected by any of these organic solvents.…”