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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Effects of Calcium Ions on the Thermostability and Spectroscopic Properties of the LH1-RC Complex from a New Thermophilic Purple Bacterium Allochromatium tepidum
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Effects of Calcium Ions on the Thermostability and Spectroscopic Properties of the LH1-RC Complex from a New Thermophilic Purple Bacterium Allochromatium tepidum

机译：钙离子对新嗜热紫色细菌对抗粒子的LH1-RC复合物热稳定性和光谱性能的影响

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摘要

The light harvesting-reaction center (LH1-RC) complex from a new thermophilic purple sulfur bacterium Allochromatium (Alc.) tepidum was isolated and characterized by spectroscopic and thermodynamic analyses. The purified Alc. tepidum LH1-RC complex showed a high thermostability comparable to that of another thermophilic purple sulfur bacterium Thermochromatium tepidum, and spectroscopic characteristics similar to those of a mesophilic bacterium Alc. vinosum. Approximately 4-5 Ca2+ per LH1-RC were detected by inductively coupled plasma atomic emission spectroscopy and isothermal titration calorimetry. Upon removal of Ca2+, the denaturing temperature of the Alc. tepidum LH1-RC complex dropped accompanied by a blue-shift of the LH1 Q(y) absorption band. The effect of Ca2+ was also observed in the resonance Raman shift of the C3-acetyl vC=O band of bacteriochlorophyll-a, indicating changes in the hydrogen-bonding interactions between the pigment and LH1 polypeptides. Thermodynamic parameters for the Ca2+-binding to the Alc. tepidum LH1-RC complex indicated that this reaction is predominantly driven by the largely favorable electrostatic interactions that counteract the unfavorable negative entropy change. Our data support a hypothesis that Alc. tepidum may be a transitional organism between mesophilic and thermophilic purple bacteria and that Ca2+ is one of the major keys to the thermostability of LH1-RC complexes in purple bacteria.
机译：通过光谱和热力学分析分离出来自新的嗜热紫硫硫菌异种酸铵（ALC，ALC）Tepidum的光学反应中心（LH1-RC）复合物。纯化的ALC。 Tepidum LH1-RC复合物显示出与另一种热嗜热紫硫磺菌热粒子酸Tepidum的热稳定性相当，以及类似于嗜苯胺菌ALC的光谱特性。 vinosum。通过电感耦合等离子体原子发射光谱和等温滴定量热法检测约4-5Ca2 + /每LH1-RC。除去Ca2 +后，ALC的变性温度。 Tepidum LH1-RC复合物伴随着LH1 Q（Y）吸收带的蓝色偏移。在Bacteriochorophl-A的C3-乙酰基Vc = O带的共振拉曼偏移中也观察到Ca2 +的效果，表明颜料和LH1多肽之间的氢键相互作用的变化。 Ca2 +的热力学参数 - 粘合到ALC。 Tepidum LH1-RC复合物表明，该反应主要受到抵消不利的负熵变化的主要良好的静电相互作用。我们的数据支持ALC的假设。 Tepidum可以是嗜钠和嗜热紫色细菌之间的过渡生物，并且Ca2 +是紫色细菌中LH1-RC复合物热稳定性的主要键之一。

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