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991.
Essential oil nanoemulsions have been proven to have stronger antimicrobial effects compared to the essential oil alone or coarse emulsion. Sonoporation could be the promising candidate to trigger a synergistic effect with thyme essential oil nanoemulsion (TEON) and produce a more effective antibacterial efficacy. Therefore, in this study, the bactericidal effects of ultrasound (US) in combination with TEON treatments against Escherichia coli (E. coli) O157:H7 were investigated. The remarkable synergistic effects of US (20 kHz, 255 W/cm2, 9 min) and TEON (0.375 mg/mL) treatments at 22 °C reduced E. coli O157:H7 populations by 7.42 ± 0.27 log CFU/mL.The morphological changes of cells exposed to different treatments were observed by scanning electron microscopy and transmission electron microscopy. The results showed that the synergistic effects of the ultrasound and TEON treatments altered the morphology and interior microstructure of organism cells. Laser scanning confocal microscopy (LSCM) images revealed that the combination treatments of ultrasound and TEON altered the permeability of cell membranes, and this affected the integrity of E. coli O157:H7 cells. This was further indicated by the high amounts of nucleic acids and proteins released from these cells following treatment.The results from this study illustrated the mechanisms of the synergistic effects of sonoporation and TEON treatments and provided valuable information for their potential in food pasteurization. 相似文献
992.
This study investigated effects of ultrasound on the contents of peptide and soluble protein, antioxidant activity, functionalities and structural characteristics of fermented soybean meal (FSBM) with Bacillus subtilis systematically. The results showed that there were significant effects of ultrasound treatments (frequency, treatment time and power density) on the contents of peptide and soluble protein (p < 0.05). Under the optimum ultrasound conditions (power density of 0.08 W/mL, frequency of 33 kHz and treatment time of 1 h) by single factor experiment, the contents of peptide and soluble protein increased by 31.27% and 18.79% compared to those of the control, respectively. Additionally, the in vitro antioxidant activity (•OH scavenging rate, Fe2+ chelating capacity and DPPH radical scavenging rate) and functional properties (emulsifying activity and emulsifying stability) of FSBM were found to be noticeably improved by ultrasound (p < 0.05). The fourier transform infrared (FTIR) spectroscopy revealed that ultrasound caused protein molecules to unfold with a decrease content of α-helix and β-turn and an increase in the proportion of β-sheet and random coil. Besides, atomic force microscope (AFM) results indicated that ultrasonication generally increased the surface roughness of protein and the protein sonicated with higher frequency (≥33 kHz) exhibited a greater height compared to lower frequency ultrasonication. Structure-activity relationship analysis illustrated that there was a good linear relationship between •OH scavenging rate and β-sheet/β-turn with Pearson’s correlation coefficient r of −0.86/0.90. Collectively, the selection of ultrasonic parameters is essential for the preparation of functional protein and bioactive peptide by enhancing fermentation of agroindustrial by-products. 相似文献
993.
番荔枝内酯————明日抗癌之星 总被引:8,自引:3,他引:8
本文介绍一类近年来被发现于番荔枝科(Annonaceae)植物中的强抗肿瘤活性化合物----番荔枝内酯(annonaceousacetogenin) , 从这类化合物的结构特点, 生理活性, 生源假说, 化学合成等几个方面综述了在该领域的氧基状况 . 相似文献
994.
995.
The methanolysis of poly(triphenylmethyl methacrylate) (PTrMA) and its copoly-mers P(TrMA-co-MMA), P(TrMA-b-MMA) has been studied in the presence of anhydrousmethanol at 40℃ by electroconductometric method. It has been found that the methanoly-sis stability can be obviously improved for the copolymer, especially, the radom copolymer,P(TrMA-co-MMA). 相似文献
996.
997.
998.
999.
合成了3个新的SOD模拟配合物:[Cu(Phen)(L-Gln)(H2O)]Cl·2H2O
(1)、[Cu(Phen)(L-Ala)(H2O)]Cl·4H2O (2)、[Cu(Phen)(L-Thr)(H2O)]Cl·2H2O
(3) [Phen(1,10-邻菲咯啉)、L-Gln(谷氨酰胺)、L-Ala(丙氨酸)、L-Thr(苏氨酸)]。用元素分析、摩尔电导、红外光谱、紫外-可见光谱对配合物进行了表征。用X-射线衍射对配合物[Cu(Phen)(L-Gln)(H2O)]Cl·2H2O的晶体结构进行了测定。用氯化硝基四氮唑蓝(NBT)光还原法对这3个配合物催化歧化超氧阴离子自由基(O2- ·)的能力进行了测定。结果表明:这些配合物具有较高的SOD活性, 催化速率常数KQ分别为1.58 ×
107 mol-1·L·s-1、5.65 × 107 mol-1·L·s-1、0.83 ×
107 mol-1·L·s-1。 相似文献
1000.
镧、钕柠檬酸配合物对纤维素酶活性的影响及其机制的探讨 总被引:1,自引:0,他引:1
研究了不同稀土浓度的镧、钕柠檬酸配合物溶液对纤维素酶水解不同纤维素底物的活性的影响规律,并对其作用机制进行了分析:用沉淀法分别合成了镧、钕柠檬酸配合物;用EDTA络合滴定法分析了镧、钕在配合物中的含量;用红外光谱法对镧、钕柠檬酸配合物进行了表征;用DNS试剂法测定了不同稀土浓度的镧、钕柠檬酸配合物溶液对纤维素酶水解不同纤维素底物的酶活性。结果表明:柠檬酸中羧基脱去质子后与镧、钕离子配位,在合适浓度时,两个配合物对纤维素酶水解滤纸、羧甲基纤维素钠、纤维二糖的活性均有最大的激活作用,钕配合物的激活效果好于镧配合物。 相似文献