转氨酶被认为是一种绿色、高效制备手性胺的催化剂。由于自然界中的转氨酶热稳定性较差,因此开发热稳定性较好、可以适应复杂工业生产条件的转氨酶更具有意义。利用计算机虚拟筛选来提高转氨酶M16AT((R)-enantioselective type Ⅳ amine...转氨酶被认为是一种绿色、高效制备手性胺的催化剂。由于自然界中的转氨酶热稳定性较差,因此开发热稳定性较好、可以适应复杂工业生产条件的转氨酶更具有意义。利用计算机虚拟筛选来提高转氨酶M16AT((R)-enantioselective type Ⅳ amine transaminase from Mycobacterium sp.ACS1612)热稳定性,首先使用AlphaFold2预测转氨酶M16AT结构,然后利用Discovery Studio对转氨酶氨基酸进行虚拟突变,通过计算机辅助计算突变体的能量变化对突变体库进行虚拟筛选,最后选择有益突变体进行突变,实验确认最佳突变体为A263F。在45℃时,A263F突变体剩余酶活相较于野生型转氨酶提高了30个百分点,A292W突变体在40~65℃的区间内也表现出优于野生型蛋白的活性。研究展示了通过氨基酸突变引入更多疏水作用力,从而增强蛋白质在高温环境下稳定性的方法,为其他酶的定向改造提供了一种可借鉴的策略。展开更多
We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations...We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.展开更多
文摘转氨酶被认为是一种绿色、高效制备手性胺的催化剂。由于自然界中的转氨酶热稳定性较差,因此开发热稳定性较好、可以适应复杂工业生产条件的转氨酶更具有意义。利用计算机虚拟筛选来提高转氨酶M16AT((R)-enantioselective type Ⅳ amine transaminase from Mycobacterium sp.ACS1612)热稳定性,首先使用AlphaFold2预测转氨酶M16AT结构,然后利用Discovery Studio对转氨酶氨基酸进行虚拟突变,通过计算机辅助计算突变体的能量变化对突变体库进行虚拟筛选,最后选择有益突变体进行突变,实验确认最佳突变体为A263F。在45℃时,A263F突变体剩余酶活相较于野生型转氨酶提高了30个百分点,A292W突变体在40~65℃的区间内也表现出优于野生型蛋白的活性。研究展示了通过氨基酸突变引入更多疏水作用力,从而增强蛋白质在高温环境下稳定性的方法,为其他酶的定向改造提供了一种可借鉴的策略。
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11473073, 11403105, 11633009 and 11661161013)the Science and Technology Development Fund of Macao (Grant Nos. 039/2013/A2 and 017/2014/A1)+2 种基金the innovative and interdisciplinary program by CAS (Grant No. KJZDEW-Z001)the Natural Science Foundation of Jiangsu Province (Grant No. BK20141509)the Foundation of Minor Planets of Purple Mountain Observatory
文摘We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.
