微生物视紫红质,一种关键的感光蛋白,在光遗传学等不同领域获得了广泛的应用,生物技术,生物装置,等。然而,目前的细菌视紫红质都是跨膜蛋白,这既使光反应机理的研究变得复杂,又限制了其进一步的应用。因此,微生物视紫红质的特定模拟物不仅可以为理解机理提供更好的模型,而且可以扩展应用。由于合成的便利性和突变后的稳定性,人蛋白CRABPII被证明是设计视紫红质模拟物的良好模板。最近,Geiger等人。设计了一种新的基于CRABPII的模拟M1-L121E微生物视紫红质与13-cis,辐射后的syn(13C)异构化。然而,与天然微生物视紫红质相比,它仍然是一个问题,特别是,在光反应动力学方面。在这篇文章中,我们通过测量其瞬态吸收光谱来研究该模拟物的激发态动力学。我们的结果表明,在pH8的模拟M1-L121E溶液中有两种成分,称为质子化席夫碱(PSB)和非质子化席夫碱(USB)状态。在这两个州,从13顺式的光反应过程,syn(13C)为全反式,反(AT)比相反方向快。此外,PSB状态下的光反应过程比USB状态下的光反应过程快。我们将PSB状态的异构化时间与微生物视紫红质的异构化时间进行了比较。我们的发现表明M1-L121E在PSB异构化的一般模式中表现出与微生物视紫红质相似的行为,其中从13C到AT的异构化比其相反方向快得多。然而,我们的结果还揭示了模拟相对于天然微生物视紫红质的激发态动力学的显着差异,包括较慢的PSB异构化速率以及不寻常的USB光反应动力学在pH=8。通过阐明模拟M1-L121E的独特特征,这项研究增强了我们对微生物视紫红质模拟物及其潜在应用的理解。
Microbial
rhodopsin, a pivotal photoreceptor protein, has garnered widespread application in diverse fields such as optogenetics, biotechnology, biodevices, etc. However, current microbial rhodopsins are all transmembrane proteins, which both complicates the investigation on the photoreaction mechanism and limits their further applications. Therefore, a specific mimic for microbial
rhodopsin can not only provide a better model for understanding the mechanism but also can extend the applications. The human protein CRABPII turns out to be a good template for design mimics on rhodopsin due to the convenience in synthesis and the stability after mutations. Recently, Geiger et al. designed a new CRABPII-based mimic M1-L121E on microbial
rhodopsin with the 13-cis, syn (13C) isomerization after irradiation. However, it still remains a question as to how similar it is compared with the natural microbial
rhodopsin, in particular, in the aspect of the photoreaction dynamics. In this article, we investigate the excited-state dynamics of this mimic by measuring its transient absorption spectra. Our results reveal that there are two components in the solution of mimic M1-L121E at pH 8, known as protonated Schiff base (PSB) and unprotonated Schiff base (USB) states. In both states, the photoreaction process from 13-cis, syn(13C) to all-trans,anti (AT) is faster than that from the inverse direction. In addition, the photoreaction process in the PSB state is faster than that in the USB state. We compared the isomerization time of the PSB state to that of microbial
rhodopsin. Our findings indicate that M1-L121E exhibits behaviors similar to those of microbial rhodopsins in the general pattern of PSB isomerization, where the isomerization from 13C to AT is much faster than its inverse direction. However, our results also reveal significant differences in the excited-state dynamics of the mimic relative to the native microbial rhodopsin, including the slower PSB isomerization rates as well as the unusual USB photoreaction dynamics at pH = 8. By elucidating the distinctive characteristics of mimics M1-L121E, this study enhances our understanding of microbial rhodopsin mimics and their potential applications.