Water-soluble chlorophyll protein (WSCP): Biological function, photophysics, and protein-directed assembly of nanoparticles

水溶性叶绿素蛋白(WSCP)是一种罕见的叶绿素结合蛋白，具有以下特点：(1)它非常稳定(耐沸水数小时)；(2)每个约20 kDa的亚基与不超过1个叶绿素a或b分子结合，不与类胡萝卜素结合。WSCP的生物学功能尚不清楚，根据最近在拟南芥花器官中高度积累WSCP的发现，本项目将致力于这一问题的部分研究。四聚体WSCP中叶绿素的数量少，相互作用密切，已知的WSCP同系物的分子结构，以及对重组蛋白进行修饰的可能性，使WSCP成为研究叶绿素-叶绿素和叶绿素-蛋白质相互作用的有用模型。这些研究将由几个光谱组完成，我们将通过向他们提供生物材料来与他们合作。最后，我们将利用功能化的重组WSCP四聚体作为稳定的支架来组织纳米颗粒的寡聚体(NPs)。这些可以是半导体NPs(量子点)，它们能够将其激发能量转移到WSCP四聚体中心的一个或两个叶绿素分子。更令人兴奋的是，将WSCP夹在两个Au纳米粒子之间的可能性；由于局部场增强和纳米天线热点处发射速率的增加，这种安排有望显著增强WSCP的荧光。各种WSCP-NP结构将在单分子水平上和整体上进行研究。提案的所有部分将共享在该项目中构建的重组WSCP的修改版本。此外，项目部分将从获得的关于WSCP的生化和光谱特性的信息中受益。

Water-soluble chlorophyll protein (WSCP) is an unusual chlorophyll-binding protein in that (i) it is extremely stable (withstanding boiling water for hours), and (ii), each subunit of about 20 kDa binds no more than 1 chlorophyll a or b molecule and no carotenoid. The biological function of WSCP is unknown, and part of this project will be dedicated to this question, based on the recent finding of highly accumulated WSCP in flower organs of Arabidopsis. The small number of chlorophylls and their close interaction in tetrameric WSCP, the known molecular structure of one WSCP homologue, and the possibility to modify the recombinant protein make WSCP a useful model to study chlorophyll-chlorophyll and chlorophyll-protein interactions. These studies will be done by several spectroscopy groups with whom we will collaborate by providing them with biological material. Finally, we will take advantage of functionalized recombinant WSCP tetramers, to use them as a stable scaffold for organizing oligomers of nanoparticles (NPs). These can be semiconductor NPs (quantum dots) which are able to transfer their excitation energy to the one or two chlorophyll molecules in the center of the WSCP tetramer. Even more exciting is the possibility of sandwiching WSCP between two Au NPs; this arrangement is expected to enhance the WSCP fluorescence drastically due to the local field enhancement and the increased emission rate in the hot spot of the nanoantenna. The various WSCP-NP constructs will be studied on the single-molecule level and in bulk. All sections of the proposal will share the modified versions of recombinant WSCP constructed in this project. Moreover, the project parts will mutually benefit from the information obtained about the biochemical and spectroscopic properties of WSCP.