分离自苏云金芽胞杆菌的首例细菌乌头酸异构酶TbrA的酶学性质研究

【目的】乌头酸异构酶(aconitate isomerase,AI)可介导具有多重生物学活性及应用潜力的小分子物质反式乌头酸(trans-aconiticacid,TAA)的合成。本文通过表征来自苏云金芽胞杆菌的生物体首条AI基因(tbrA)的产物——TbrA蛋白的催化性质,填补人们对于AI酶学特性的认识。【方法】我们利用大肠杆菌Rosetta菌株和Ni^(2+)柱亲和纯化获得了His6-TbrA蛋白,并在体外通过HPLC检测了产物生成及对应酶活。【结果】TbrA蛋白的最适pH、温度与离子强度分别为8.0,37°C和25 mmol/L。TbrA在10°C时仍保留约60%的活性,展现了较好的耐低温特性。金属离子Mg^(2+)、Ca^(2+)与还原剂DTT可显著增强TbrA活性,而Fe^(2+)、Cu^(2+)、Zn^(2+)、Mn^(2+)则强烈抑制TbrA活性。TbrA将顺式乌头酸(cis-aconitic acid,CAA)异构为TAA的正反应Km、Vmax、kcat、kcat/Km值分别为6.25mmol/L、1.39μmol/(L·s)、4.081/s、0.65L/(mmol·s),将TAA异构为CAA的逆反应的上述数值分别为71.50mmol/L、4.17μmol/(L·s)、12.25 1/s、0.17 L/(mmol·s)。【结论】AI酶蛋白TbrA可以在温和的理化条件下表现出最高活性,且更倾向于合成TAA。本研究定量描述了TbrA催化特性,为其今后应用于TAA工业生物合成奠定基础。

Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca^(2+)-Doped CsPbI_(3) Nanocrystals

α-CsPbI3 nanocrystals(NCs)with poor stability prevent their wide applications in optoelectronic fields.Ca^(2+)(1.00Å)as a new B-site doping ion can successfully boost CsPbI3 NC performance with both improved phase stability and optoelectronic properties.With a Ca^(2+)/Pb^(2+)ratio of 0.40%,both phase and photoluminescence(PL)stability could be greatly enhanced.Facilitated by increased tolerance factor,the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120℃.The PL stability of its solution could be preserved to 83%after 147 days in ambient condition.Even using UV light to accelerate aging,the T_(50) of PL could boost 1.8-folds as compared to CsPbI_(3) NCs.Because Ca^(2+) doping can dramatically decrease defect densities of films and reduce hole injection barriers,the red light-emitting diodes(LEDs)exhibited about triple enhancement for maximum the external quantum efficiency(EQE)up to 7.8%and 2.2 times enhancement for half-lifetime of LED up to 85 min.We believe it is promising to further explore high-quality CsPbI_(3) NC LEDs via a Ca^(2+)-doping strategy.

Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca^(2+)-Doped CsPbI_(3)Nanocrystals

α-CsPbI_(3)nanocrystals(NCs)with poor stability prevent their wide applications in optoelectronic fields.Ca^(2+)(1.00Å)as a new B-site doping ion can successfully boost CsPbI_(3)NC performance with both improved phase stability and optoelectronic properties.With a Ca^(2+)/Pb^(2+)ratio of 0.40%,both phase and photoluminescence(PL)stability could be greatly enhanced.Facilitated by increased tolerance factor,the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120℃.The PL stability of its solution could be preserved to 83%after 147 days in ambient condition.Even using UV light to accelerate aging,the T50 of PL could boost 1.8-folds as compared to CsPbI_(3)NCs.Because Ca^(2+)doping can dramatically decrease defect densities of films and reduce hole injection barriers,the red light-emitting diodes(LEDs)exhibited about triple enhancement for maximum the external quantum efficiency(EQE)up to 7.8%and 2.2 times enhancement for half-lifetime of LED up to 85 min.We believe it is promising to further explore high-quality CsPbI_(3)NC LEDs via a Ca^(2+)-doping strategy.