Triacylglycerols are considered one of the most promising feedstocks for biofuels. Phospholipid:diacylglycerol acyltransferase (PDAT), responsible for the last step of triacylglycerol synthesis in the acyl-CoA-independent pathway, has attracted much attention by catalyzing membrane lipid transformation. However, due to lack of biochemical and enzymatic studies, PDAT has not carried forward in biocatalyst application. Here, the PDAT from Saccharomyces cerevisiae was expressed in Pichia pastoris. The purified enzymes were studied using different acyl donors and acceptors by thin layer chromatography and gas chromatography. In addition of the preferred acyl donor of PE and PC, the results identified that ScPDAT was capable of using broad acyl donors such as PA, PS, PG, MGDG, DGDG, and acyl-CoA, and ScPDAT was more likely to use unsaturated acyl donors comparing 18:0/18:1 to 18:0/18:0 phospholipids. With regard to acyl acceptors, ScPDAT preferred 1,2 to 1,3-diacylglycerol (DAG), while 12:0/12:0 DAG was identified as the optimal acyl acceptor, followed by 18:1/18:1 and 18:1/16:0 DAG. Additionally, ScPDAT reveals esterification activity that can utilize methanol as acyl acceptor to generate fatty acid methyl esters. The results fully expand the enzymatic selectivity of ScPDAT and provide fundamental knowledge for synthesis of triacylglycerol-derived biofuels.
Using the conventional volumetric method in unsteady-state relative permeability measurements for unconventional gas reservoirs, such as coal and gas shale, is a significant challenge because the movable water volume in coal or shale is too small to be detected. Moreover, the dead volume in the measurement system adds extra inaccuracy to the displaced water determination. In this study, a low-field nuclear magnetic resonance (NMR) spectrometer was introduced into a custom-built relative permeability measurement apparatus, and a new method was developed to accurately quantify the displaced water, avoiding the drawback of the dead volume. The changes of water in the coal matrix and cleats were monitored during the unsteady-state displacement experiments. Relative permeability curves for two Chinese anthracite and bituminous coals were obtained, matching the existing research results from the Chinese coalbed methane area. Moreover, the influences of confining pressure on the shape of the relative permeability curve were evaluated. Although uncertainties and limits exist, the NMR-based method is a practical and applicable method to evaluate the gas/water relative permeability of ultra-low permeability rocks. 相似文献
Thanks to the pure blue emitting, high planarity, electron rich and ease of chemical modification, pyrene has been thoroughly investigated for applications in organic electronics such as organic light emitting diodes (OLEDs), organic field effect transistors (OFETs), and organic solar cells (OSCs). Especially, great progresses have been made of pyrene-based organic semiconductors for OFETs in past decades. Due to the difference of molecular structure, pyrene-based organic semiconductors are divided into three categories, pyrene as terminal group, pyrene as center core and fused pyrene derivatives. This minireview gives a brief introduction of the structure-property relationship and application in OFETs about most of pyrene-based semiconducting materials since 2006, illustrating that pyrene is a good building block to construct semiconductors with superior transport property for OFETs. Finally, we provide a summary concerning the methodology to improve the transport property of the pyrene-based semiconducting materials as well as an outlook. 相似文献
We review recent progress in studying silicate, carbonate, and metallic liquids of geo-logical and geophysical importance at high pressure and temperature, using the large-volume high-pressure devices ... 相似文献