The glutathione S-transferase (GST) system is useful for increasing protein solubility and purifying soluble GST fusion proteins. However, purifying half of the GST fusion proteins is still difficult, because they are virtually insoluble under non-denaturing conditions. To optimize a simple and rapid purification condition for GST-pyruvate kinase muscle 2 (GST-PKM2) protein, we used 1% sarkosyl for lysis and a 1:200 ratio of sarkosyl to Triton X-100 (S-T) for purification. We purified the GST-PKM2 protein with a high yield, approximately 5 mg/L culture, which was 33 times higher than that prepared using a conventional method. Notably, the GST-high-temperature requirement A2 (GST-HtrA2) protein, used as a model protein for functional activity, fully maintained its proteolytic activity, even when purified under our S-T condition. This method may be useful to apply to other biologically important proteins that become highly insoluble in the prokaryotic expression system. [BMB reports 2011; 44(4): 279-284]
Chemical melting agents are traditional methods for snow-removing applications. Due to their adverse environmental impact, thermo-snow melting pavements with conductive fillers are becoming frequently used. In this study, the thermo-physical properties of graphite-modified asphalt mixtures (GMAM) and the sensitivity of snow melting pavements were investigated. The microstructure of GMAM was analysed at extremely high magnification to observe the distribution of conductive fillers in the mixture. Two different mixing processes were adopted to mould asphalt mixtures: dry mixing and wet mixing. The conductivity was compared to evaluate the effects of asphalt mixture preparing methods and the quantity of graphite on the thermal properties of GMAM. A one-dimensional finite difference analysis was performed to determine the efficiency of GMAM for snow melting processes. Microstructure analysis was conducted on scanning election microscope (SEM) images of the fractured surface of specimens. Thermal testing and analysis results indicated that graphite improves the conductivity of asphalt mixtures and shortens the time required for snow melting. The numerical analysis results showed that environmental factors have significant effects on pavement surface temperature, and adjusting the heat source temperature can substitute the changes in environmental conditions. According to the micro-analysis, graphite particles form clusters throughout the asphalt mixture.
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