Quantitative Studies of Chiral Induced Spin Selectivity in Amino Acids and Peptides

电子是构成原子和分子的基本粒子之一。 电子的两个关键特征是它的负电荷和自旋（电子绕轴旋转，就像旋转的陀螺一样）。很长一段时间以来，科学家们已经知道，电子在分子中的运动取决于它的电荷如何被吸引到带正电的原子核上，并被其他电子排斥。最近发现，电子自旋的方向可以改变电子在手性分子中移动的能力，这一过程称为自旋过滤。当一个分子的镜像不能相互叠加时，它就是手性的;我们的右手和左手就是手性物体的例子。最近发现电子的自旋也可以影响其运动，特别是当与手性分子相互作用时，这为化学开辟了新的可能性。 美国匹兹堡大学的大卫沃尔德克教授和他的学生们在这个由化学系化学结构、动力学和机理-A项目资助的项目中，利用电学和电化学方法将手性分子的自旋过滤性质与其分子结构联系起来。 他们的发现可能对控制化学反应中的手性具有重要意义，这可能有利于新药的开发和为先进制造业创造更好的催化剂。从事该项目的学生将受益于与匹兹堡和以色列其他科学家的合作和多学科活动。沃尔德克教授还在建立一个初中和高中科学教师网络，以促进对科学的兴趣和学习。手性诱导的自旋选择性（CISS）效应挑战了传统的智慧的大小的自旋轨道耦合在有机分子中，并提出了有趣的影响手性的作用，在电子转移过程中。虽然许多实验证明CISS的范围内的分子，需要进行定量测量的现象，并将其与其他分子特性。实验研究探讨了CISS产生的自旋过滤。 霍尔探针测量被用来量化的磁化，所产生的膜包括手性分子，具有和不具有手性二级结构。 研究人员还测量了自旋极化，并将其与分子的固有特性进行了比较，例如它们的手性光学响应和极化率。电化学测量被用来量化通过手性分子的电化学电荷转移反应中的自旋过滤，并将其与霍尔探针研究相同的分子进行比较。考虑到自旋可能是化学转化的一个重要限制因素，并且许多生物分子都是手性的，CISS效应可能在化学和生物学方面都具有重要意义。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Electrons are one of the basic particles that make up atoms and molecules. Two key features of an electron are its negative charge and its spin (the electron spins about an axis, like a spinning top). For a long time, scientists have known that an electron's motion through molecules depends on how it's charge is attracted to the positively-charged nuclei and repelled by the other electrons. It was recently discovered that the direction of an electron's spin could alter the ability of an electron to move through a chiral molecule, in a process called spin-filtering. A molecule is chiral when it's mirror images cannot be superimposed on one another; Our right and left hands are examples of chiral objects. The recent finding that the electron's spin can also affect its motion, particularly when interacting with a chiral molecule, opens new possibilities in chemistry. In this project funded by the Chemical Structure, Dynamics and Mechanism-A program of the Chemistry Division, Professor David Waldeck of the University of Pittsburgh and his students are using electrical and electrochemical methods to correlate the spin filtering properties of chiral molecules with their molecular structures. Their discoveries could have important implications for controlling chirality in chemical reactions, which could benefit the development of new pharmaceuticals and the creation of better catalysts for advanced manufacturing. Students working on this project benefit from collaborative and multidisciplinary activities with other scientists in Pittsburgh and Israel. Professor Waldeck is also building a network of middle school and high school science teachers to promote interest and learning in science. The chiral induced spin selectivity (CISS) effect challenges the conventional wisdom about the magnitude of spin-orbit coupling in organic molecules and raises interesting implications for the role of chirality in electron transfer processes. While numerous experiments demonstrate CISS for a range of molecules, the need exists to perform quantitative measurements of the phenomenon and correlate it with other molecular properties. The experimental studies explore the spin-filtering that arises from CISS. Hall probe measurements are used to quantify the magnetization that arises from films comprising chiral molecules, both with and without chiral secondary structure. The researchers also measure spin polarization and compare it with intrinsic molecular properties, such as their chiro-optical response and their polarizabilities. Electrochemical measurements are used to quantify the spin filtering in electrochemical charge transfer reactions through chiral molecules and compared it with Hall probe studies on the same molecules. Given that spin can be an important constraint for chemical transformations and many biomolecules are chiral, the CISS effect could have important implications in both chemistry and biology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.