Zhimeng Liu

Preparation of waterborne polyurethanes based on the organic solvent-free process

A green waterborne polyurethane (WPU) was prepared based on an organic solvent-free process, using sodium 2,4-diaminobenzenesulfonate (SDBS) as a chain extender. Water was only used to dissolve the solid reactants and reduce the viscosity, obtaining the homogenized reaction mixture. Characterization results showed that this green WPU presented similar mechanical properties and water resistance with conventional WPU whose synthesis process involved organic solvents. In addition, the use of SDBS eliminated the employment of catalysts and reduced the reaction time and temperature of the chain extension step, resulting in the conservation of energy.

Preparation and thermal properties of crosslinked polyurethane/lauric acid composites as novel form stable phase change materials with a low degree of supercooling

In this article, a series of crosslinked polyurethane/lauric acid composites was prepared as form stable phase change materials (FSPCMs) through a brief and solvent-free method. In the FSPCMs, lauric acid functioned as a phase change substance, and crosslinked polyurethane simultaneously functioned as a supporting material and phase change substance. Compared with traditional supporting materials in FSPCMs, the crosslinked polyurethane here obviously reduces the loss of latent heat from the supporting material and reduces the degree of supercooling of the obtained FSPCMs. The obtained FSPCMs were extensively studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), polarizing microscopy (POM), differential scanning calorimetry (DSC), thermal cycling tests and thermogravimetric analysis (TGA). The FTIR confirmed the chemical structure of the obtained FSPCMs. The XRD and POM results indicated that the FSPCMs exhibit comprehensive crystalline properties of polyurethane and lauric acid. DSC data showed that the FSPCMs have superior phase change properties with the phase change temperature and latent heat in the range of 26–38 °C and 90–131 J g−1. Moreover, low or no supercooling of the obtained FSPCMs was detected by DSC. The phase change temperature is suitable in the fields of solar energy saving and building engineering. Thermal cycling tests and thermogravimetric analysis (TGA) proved the good thermal reliability and stability of the obtained FSPCMs.

Preparation, characterization and properties of poly(lactic acid)/poly(1,4-butylene adipate) blends for biodegradable packaging materials

Poly(lactic acid) (PLA)/poly(1,4-butylene adipate) (PBA) blends with different PBA content were directly prepared via melt blending as potential biodegradable packaging materials. PBA with 1000 g/mol number average molecular weight was served as plasticizer to improve PLA properties. The morphological, thermal and mechanical properties of the blends were extensively investigated by scanning electron microscope (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile and impact tests and thermogravimetry (TG). The results show that the degree of crystallinity of PLA increased with increasing PBA content. The addition of PBA (20 wt%) result in the positive effect on the elongation at break and toughness, which increased from 7.9% to 74.4% and from 3.9 kJ/m2 to 12.6 kJ/m2, respectively. Meanwhile, the migration tests indicate that PBA exhibits excellent lower migration ratio compared with citrate esters.

Expression in Escherichia coli of the gene encoding ascorbate peroxidase from Brassica napus enhances salt tolerance of bacterial cells

Ascorbate peroxidase (APX) is an important enzyme to scavenge the reactive oxygen species (ROS), which are often caused by the salt stress. Here, APX cDNA from Brassica napus was amplified by RT-PCR and cloned into the prokaryotic expression vector pGEX-6p-1 to express BnAPX as a glutathione S-transferase (GST) fusion protein. The recombinant expression plasmid was then transformed into Escherichia coli BL21 (DE3) and induced with 0.2 mM IPTG at 28°C. The enzyme activity analysis of the induced protein showed the GST-APX protein had the similar enzyme activity with the other found APXs, which decompose H2O2. Moreover, the GST-APX fusion protein was purified by affinity chromatography using the glutathione-Sepharose 4B column. The purified GST-APX protein was then used to immunize rabbits to obtain the anti-BnAPX serum, which was suitable to recognize both the recombinant exogenous BnAPX and the endogenous BnAPX in vivo by western blotting and the immunohistochemical experiment. Furthermore, the immuno-fluorescent microscopy observation revealed that BnAPX was expressed in the chloroplasts. Finally, the bacteria expressing BnAPX grew much faster in the presence of 3% NaCl than the control cells, indicating that the transformant expressing BnAPX acquired resistance to salt stress.

Overexpression of UDP-glucosyltransferase 71C5 increases glucose tolerance in Arabidopsis thaliana

Glucosyltransferases (GTs) catalyze transfer of sugar moieties to a wide range of acceptor molecules, which could be proteins, lipids, or low-molecular-weight lipophilic acceptors. As a subfamily of GTs, uridine diphosphate (UDP)-glucosyltransferases (UGTs), which function is glycosylation of low-molecularweight lipophilic acceptors, has drawn increasing attention. In this study, it was found that UGT71C5 expression in Arabidopsis thaliana treated by 4% glucose could be induced to approximately 250 and 180% of that in the wild type (WT) at both transcriptional and translational levels. Three independent lines overexpressing UGT71C5 were obtained and quantitatively analyzed. It was shown that the average root length of 35S::UGT71C5 transgenic lines was doubled as compared with WT on MS supplemented with 4% glucose. To our knowledge, in higher plants glucose acts as both nutrient and regulatory molecule, which controls many aspects of physiology and development, and the high levels of glucose could arrest glucose-mediated root elongation in plants. Our work suggests that overexpression of UGT71C5 could increase glucose tolerance of A. thaliana. This study could provide insights into the function of UGT71C5 in plants.

Functional characterization and analysis of the Arabidopsis UGT71C5 promoter region.

In the present study, we isolated an Arabidopsis promoter, UGT71C5, and analyzed its role in the regulation of the light response mechanism. We constructed a fusion vector pBI121-pU-GUS by integrating the UGT71C5 promoter upstream of the GUS reporter gene in pBI121, and then transferred this vector into Arabidopsis plants. The GUS activity of the transgenic plants was detected using a spectrophotometer under normal growth conditions as well as under light, drought, and ABA stress-treatments. The obtained results indicated that the GUS activity of transgenic plants ranged in between the activities observed in wild-type and 35S transgenic plants, which were used as positive control. Light stress for 8 and 12 h increased the GUS activity in transgenic plants by 3 and 4 times, respectively, compared to the activity in these plants under normal conditions. No such change in the GUS activity was observed under drought and ABA-treated conditions. This suggests that the UGT71C5 promoter is light inducible. Our study provides helpful insights into the elucidation of inducible promoters in Arabidopsis and the molecular mechanisms of light response.

VDAC2 involvement in the stress response pathway in Arabidopsis thaliana.

The voltage-dependent anion channel (VDAC) is the major transport protein in the outer membrane of mitochondria, and is involved in the formation of a permeable transition pore and metabolite transport. In this study, we explored the role of Arabidopsis thaliana VDAC2 (AtVDAC2) in the signal transduction pathway in Arabidopsis under salt stress. We investigated the germination rates of AtVDAC2 transgenic lines under salicylic acid (SA) treatment, and found that AtVDAC2 can affect the sensitivity of Arabidopsis to SA. Furthermore, the stomatal apertures of AtVDAC2 transgenic Arabidopsis were calculated. Results showed that the over-expression lines showed the obvious stomatal closure, while in the antisense lines, no obvious changes in stomatal apertures were found. In addition, we also detected the expression levels of salt stress and SA response-associated genes in transgenic plants and found that AtVDAC2 affected the expression of these genes. Our study investigated the role of AtVDAC2 in SA and salt stress response in Arabidopsis; our observations provide some helpful information for better understanding the direct and downstream functions of AtVDAC.