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

水溶性叶绿素蛋白（WSCP）是一种不寻常的叶绿素结合蛋白，因为（i）它非常稳定（可耐受沸水数小时），和（ii），每个约20 kDa的亚基结合不超过1个叶绿素a或B分子，不含类胡萝卜素。WSCP的生物学功能尚不清楚，本项目的一部分将致力于这一问题，基于最近发现的高度积累的WSCP在拟南芥花器官。四聚体WSCP中叶绿素的数量少，相互作用密切，一个WSCP同源物的已知分子结构，以及修饰重组蛋白的可能性，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学小组完成，我们将通过向他们提供生物材料与他们合作。最后，我们将利用功能化的重组WSCP四聚体，使用它们作为组织纳米颗粒（NP）的寡聚体的稳定支架。这些可以是半导体NP（量子点），其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。更令人兴奋的是在两个Au NP之间包裹WSCP的可能性;由于局部场增强和纳米天线的热点中增加的发射速率，预计这种布置将大幅增强WSCP荧光。将在单分子水平和批量研究各种WSCP-NP构建体。建议书的所有章节将共享本项目中构建的重组WSCP的修改版本。此外，项目部分将从WSCP的生物化学和光谱特性获得的信息中受益。

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.