Structural dynamics of water and the peptide backbone around the Schiff base associated with the light-activated process of octopus rhodopsin.
Structural dynamics of water and the peptide backbone around the Schiff base associated with the light-activated process of octopus rhodopsin.
复制标题
水和席夫碱周围肽骨架的结构动力学与章鱼视紫红质的光激活过程相关。
作者：
S. Nishimura;H. Kandori;M. Nakagawa;M. Tsuda;A. Maeda
用差示傅里叶变换红外光谱法研究了低温下章鱼视紫红质生成光中间体和异视紫红质的过程。对席夫碱、内部水分子和肽骨架的H键进行分析。席夫碱的亚胺氢在整个光中间体和未光解状态下处于相同的氢键状态。与此相反，氢键的氢的水分子，其氧可能是复杂的席夫碱的亚胺氢被改变后形成的视紫红质。相同的水分子在随后的中间体中处于不同的氢键状态，即光视紫红质和中视紫红质。这些中间体的特征还在于席夫碱的C = N键级的降低，这反映了席夫碱周围的扭曲结构。这些中间体中的极性N-H键也可归因于Schiff碱。异视紫红质中也观察到了光视紫红质和中视紫红质中水分子氢键的变化和多烯链的扰动。酸性变视紫红质的肽骨架和内部水分子的氢键状态表现出广泛的变化。这些变化的很大一部分被熄灭在碱性metarhodopsin与未质子化的席夫碱，表明在酸性metarhodopsin的肽骨架和膜内水分子的质子化的席夫碱的相互作用。
Difference Fourier transform infrared spectra were recorded for the formation of the photointermediates and isorhodopsin from octopus rhodopsin at low temperatures. Analysis was done for H bonding of the Schiff base, internal water molecules, and the peptide backbone. The imine hydrogen of the Schiff base was in the same H bonding state throughout the photointermediates and the unphotolyzed state. In contrast, H bonding of the hydrogen of the water molecule whose oxygen might be complexed with the imine hydrogen of the Schiff base was altered upon the formation of bathorhodopsin. The same water molecule was in a different H bonding state in the subsequent intermediates, lumirhodopsin and mesorhodopsin. These intermediates were also characterized by a decrease in the C = N bond order of the Schiff base as a reflection of distorted structure around the Schiff base. The polar N-H bond in these intermediates could be also ascribed to the Schiff base. Some changes in H bonding of water and the perturbation of the polyene chain in lumirhodopsin and mesorhodopsin were also observed in isorhodopsin. Acid metarhodopsin exhibited extensive changes in the H bonding states of the peptide backbone and internal water molecules. A large part of these changes was extinguished in alkaline metarhodopsin with the unprotonated Schiff base, suggesting interaction of the protonated Schiff base with the peptide backbone and intramembrane water molecules in acid metarhodopsin.