Spontaneous emulsification of detergent solubilized reaction center: protein conformational changes precede droplet growthPresented at the 17th Conference of the European Colloid & Interface Science Society, Firenze, Italy, September 21?26, 2003.
Spontaneous emulsification of detergent solubilized reaction center: protein conformational changes precede droplet growthPresented at the 17th Conference of the European Colloid & Interface Science Society, Firenze, Italy, September 21?26, 2003.
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洗涤剂增溶反应中心的自发乳化：蛋白质构象变化先于液滴生长在第十七届欧洲胶体会议上发表
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
R. Piazza
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作者：
G. Palazzo;A. Mallardi;F. Francia;Manuela Dezi;G. Venturoli;M. Pierno;Emanuele Vignati;R. Piazza
我们发现，电离的pH敏感的洗涤剂，DDAO，绑定到细菌光合反应中心（RC），诱导可逆乳化的蛋白质在一个狭窄的酸性pH范围内，导致稳定的微米RC-表面活性剂液滴。静电相互作用在相分离过程中起着关键作用，如通过离子强度效应的系统分析和通过使用阳离子洗涤剂（DTAB）所示，所述阳离子洗涤剂（DTAB）也在碱性pH下模仿DDAO的离子化形式。在我们测试的所有条件下，相分离似乎与RC的初级电子供体P的低能吸收带的15 nm蓝移相耦合。这种光谱变化强烈表明，导致相分离的表面活性剂-蛋白质相互作用也诱导了RC的构象转变。在乳化过程中记录的时间分辨可见近红外光谱表明，由P光谱位移探测的构象变化总是比液滴形成快。与这些观察结果一致，相分离影响RC光激发后的电荷重组动力学，以及从可溶性细胞色素C2到光氧化初级供体P+的电子转移。
We show that ionization of a pH-sensitive detergent, DDAO, bound to a bacterial photosynthetic reaction center (RC), induces reversible emulsification of the protein over a narrow acidic pH range, resulting in stable micrometric RC-surfactant droplets. Electrostatic interactions play a key role in the phase separation process, as shown by a systematic analysis of ionic strength effects and by the use of a cationic detergent (DTAB) that mimics, also at basic pH, the ionized form of DDAO. Under all the conditions we tested, phase segregation seems to be coupled to a 15 nm blue-shift of the low energy absorption band of the primary electron donor P of the RC. This spectral change strongly suggests that surfactant-protein interactions leading to phase separation also induce a conformational transition of the RC. Time-resolved visible-NIR spectra recorded during the emulsification process reveal that the conformational change probed by P spectral shift is always faster than droplets formation. In line with these observations, phase segregation affects charge recombination kinetics following RC photoexcitation, as well as electron transfer from soluble cytochrome c2 to the photoxidized primary donor P+.