Structure and Function of Carotenoids

类胡萝卜素是自然产生的色素，对光合作用有机体的生存是必不可少的。它们起到保护装置的作用，防止光合作用装置不可逆转的光破坏，它们的功能是捕光色素。尽管从多年的研究中获得了关于类胡萝卜素行为的一般知识，但这些分子的激发态谱和动力学仍然不是很清楚。根据光谱数据对它们的能量状态的许多指定是有争议的，激发态的确切性质以及它们在控制类胡萝卜素的生物学功能中所起的作用仍然不清楚。该项目的总体目标是阐明类胡萝卜素的激发态光谱和动力学，以揭示它们如何在自然界中发挥重要作用。计划中的实验将分析从合成的或从几个不同的光合作用有机体获得的多烯和类胡萝卜素的系统系列。此外，还将研究用修饰的叶绿素折叠的重组蛋白，或在蛋白结合色素附近进行了定点突变的重组蛋白。超快时间分辨光谱方法将用于测量激发态的光谱和动力学。这些实验将通过理论量子力学计算来扩大，以揭示将与光谱可观测值相关联的激发态组态。描述类胡萝卜素光化学行为的动力学和量子力学模型将被评估。将测试与类胡萝卜素的激发态结构和光谱性质有关的各种假设，并解决关于类胡萝卜素如何发挥作用的一些问题。广泛影响这项研究的主题与几个重要的社会主题有广泛的相关性，包括全球气候变化、生物燃料和替代太阳能转换方案的开发。该项目的一个重要方面将是对本科生和研究生的培训产生的影响，其中包括通过几项外联活动招募的人数不足群体的学生，国际和平协会将继续参加这些活动。在PI的实验室中，学生们将获得广泛的实验方法经验，包括复杂生物材料的分离和表征技术、复杂的分子光谱方法以及动力学和量子计算模型。学生将通过撰写报告和出版物以及在科学会议上发表演讲来发展组织和解决问题的技能，以从该领域的专家那里获得宝贵的批判性反馈。此外，PI将通过将该主题直接纳入大学一年级的普通化学和研究生生物和物理化学课程，以及通过公众参与的外展活动，促进对该项目的总体了解。PI将在不同的学校发表演讲，他不仅将介绍该项目的科学内容，还将介绍该项目的广泛社会影响。PI将继续在NSF赞助的REU计划中扮演积极的导师角色，在化学系，参与该计划的学生将直接参与该项目。最后，与国际知名专家建立了合作安排，这些专家将与小组中的学生自由互动，特别是与该项目相关的工作，提供全球视角，并帮助尽快实现研究成果。该项目由分子和细胞生物科学部的分子生物物理学计划和化学部的化学结构、动力学和机制以及生命过程的化学计划共同支持

Carotenoids are naturally-occurring pigments that are essential for the survival of photosynthetic organisms. They act as protective devices against irreversible photodestruction of the photosynthetic apparatus, and they function as light-harvesting pigments. Despite this general knowledge of carotenoid behavior obtained from years of investigations, the excited state spectra and dynamics of these molecules are still not well understood. Many of the assignments of their energy states from spectroscopic data are controversial, and the precise nature of the excited states and the roles they play in controlling the biological functions of carotenoids remain unclear. The overall objective of the project is to elucidate the excited state spectra and dynamics of carotenoids in order to reveal how they carry out their important roles in nature. The planned experiments will analyze systematic series of polyenes and carotenoids obtained either synthetically or from several different photosynthetic organisms. In addition, recombinant proteins refolded with modified chlorophylls, or having undergone site-directed mutagenesis in the vicinity of protein-bound pigments, will be studied. Ultrafast time-resolved spectroscopic methods will be used to measure the spectra and dynamics of the excited states. The experiments will be augmented by theoretical quantum mechanical computations to reveal the excited state configurations which will be correlated with the spectroscopic observables. Kinetic and quantum mechanical models describing the photochemical behavior of carotenoids will be evaluated. Various hypotheses pertaining to the excited state structure and spectral properties of carotenoids will be tested, and a number of issues regarding how carotenoids function will be addressed.Broader impactsThe subject of the research has broad relevance to several socially important topics including global climate change, biofuels, and the development of alternative solar energy conversion schemes. A critical aspect of this project will be its impact on the training of undergraduate and graduate students which include those from underrepresented groups recruited though several outreach activities in which the PI will continue to participate. In the laboratory of the PI, the students will gain experience in a broad spectrum of experimental approaches including the techniques for the isolation and characterization of complex biological materials, sophisticated molecular spectroscopic methodologies, and kinetic and quantum computational modeling. The students will develop organizational and problemsolving skills by writing reports and publications and making presentations at scientific meetings to obtain valuable critical feedback from experts in the field. In addition, the PI will advance general understanding of the project by incorporating the subject matter directly into the freshman-level General Chemistry and graduate Biological and Physical Chemistry courses and through outreach activities involving the general public. The PI will be giving presentations at various schools where he will speak not only about the scientific content, but also about the broad social impacts of the project. The PI will continue his active role as a mentor in the NSF-sponsored REU program in the Department of Chemistry where a participating student will work directly on the project. Finally, the PI has established collaborative arrangements with internationally-known experts who will interact freely with the students in the group specifically on work related to this project, offer a global perspective on the work, and help bring the studies to fruition as rapidly as possible.This project is jointly supported by the Molecular Biophysics program in the Division of Molecular and Cellular Biosciences and the Chemical Structure, Dynamics and Mechanism and Chemistry of Life Processes programs in the Chemistry Division