Collaborative Research: Probing Reconfigurable Nanoparticle Biointerfaces using Catalysis

迈阿密大学的马克·奈赫特教授和纽约州立大学石溪分校的阿纳托利·I·弗伦克尔教授得到了化学系大分子、超分子和纳米化学(MSN)计划的支持，以开发生物分子键合纳米颗粒，用于催化领域的独特应用。纳米粒子是令人难以置信的小材料，比人类一根头发的宽度小1000倍。为了防止这些颗粒无法控制地聚集到更大的结构上，小分子被化学结合到颗粒表面。这些分子也被称为配体，使纳米颗粒稳定地悬浮在溶液中，使其能够研究从收集太阳能到化学催化等广泛应用的材料性质。虽然这些配体非常重要，但它们通常被锁定在单一构象中，从而限制了纳米颗粒的性质。在这个项目中，克奈特教授和弗伦克尔教授正在利用生物灵感和分子设计来开发生物配体，当受到特定波长或颜色的光照射时，这种生物配体可以改变其结构。当这些生物分子被用来稳定金属纳米颗粒时，它们可以在结合到材料上时改变它们的排列，从而获得两种不同的构象，并增强单一材料的潜在性质。这些构象差异和材料性能的变化正在使用催化和先进的光谱方法进行研究，为材料设计提供了非常详细的信息。克奈特教授和弗伦克尔教授还鼓励本科生将这项研究与入门教育相结合，以鼓励学生从事与科学相关的研究和职业。此外，还计划重新安排一、二年级的普通和有机课程和实验室，以提高化学本科生的保留率。胶体金属纳米颗粒通常是使用表面钝化配体构建的，这些配体刚性地结合到无机表面，将它们锁定在单一构型中。通过远程驱动颗粒表面的界面结构以采用不同的构象，材料的性能可以根据需要进行调整。奈克特和弗伦克尔教授假设，基于多肽的纳米颗粒钝化剂可以通过外部刺激进行远程和可逆的重新配置，以采用两种不同的配置来按需控制材料性能。这种能力可以通过将光开关整合到多肽结构中来实现。由于生物分子与纳米颗粒表面的结合，光开关异构化状态的变化可以通过多肽构象传播。这种能力正在使用催化作为配体结构构象的表面探针来检验，其中反应速率的差异是可观察到的。这些差异正在被利用来实现开/关催化反应，这对多步反应可能是重要的。此外，作为这项研究的一部分，对纳米颗粒进行了先进的、原位的和操作的X射线光谱分析，以确定在光切换和催化之前、期间和之后颗粒表面结构作为配体构象的函数的变化。最后，正在研究纳米颗粒组成、大小和形状的影响，以调节基于光开关的多肽结构差异的水平，以增强对颗粒催化性能的控制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professor Marc Knecht of the University of Miami and Professor Anatoly I. Frenkel of SUNY at Stony Brook are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Division of Chemistry to develop biomolecule-bonded nanoparticles for unique applications in catalysis. Nanoparticles are incredibly small-sized materials that are 1000 times smaller than the width of one strand of human hair. To prevent these particles from uncontrollably aggregating to larger structures, small molecules are chemically bound to the particle surface. These molecules, also called ligands, keep the nanoparticles stably suspended in solution, allowing for studies of the material properties for wide ranging applications from harvesting solar energy to chemical catalysis. While these ligands are incredibly important, they are typically locked in a single conformation, thus limiting the properties of a nanoparticle. In this project, Professors Knecht and Frenkel are using biological inspiration and molecular design to develop biological ligands that can change their structure when irradiated with light of a certain wavelength or color. When these biomolecules are used to stabilize metal nanoparticles, they can change their arrangement when bound to the material, thus accessing two different conformations and enhancing the potential properties of a single material. These conformation differences and the changes to the material properties are being studied using catalysis and advanced spectroscopy methods, providing great detail to aid in material design. Professors Knecht and Frenkel are also engaging undergraduate students with the integration of this research with education at the entry level to encourage students into science related studies and careers. In addition, plans are implemented to realign the Freshman and Sophomore general and organic courses and laboratories to improve the chemistry undergraduate students' retention ratio. Colloidal metal nanoparticles are typically constructed using surface passivating ligands that are rigidly bound to the inorganic surface, locking them into a single configuration. By having the ability to remotely actuate the interfacial structure on the particle surface to adopt different conformations, the properties of the materials could be tuned on demand. Professors Knecht and Frenkel hypothesize that peptide-based nanoparticle passivants can be remotely and reversibly reconfigured via external stimuli to adopt two different configurations for on demand material property control. Such capabilities are achievable through the integration of a photoswitch into the peptide structure. Changes in the photoswitch isomerization state can be propagated through the peptide conformation due to the binding between the biomolecule and the nanoparticle surface. This capability is being examined using catalysis as a surface probe of the ligand structural conformation, where differences in reaction rates are observable. These differences are being exploited to achieve on/off catalytic reactivity, which could be important for multistep reactions. Furthermore, as part of this study, advanced, in situ and operando X-ray spectroscopic analysis of the nanoparticles are being used to identify changes in particle surface structure as a function of ligand conformation before, during, and after photoswitching and catalysis. Finally, the effects of the nanoparticle composition, size, and shape are being studied to modulate the level of photoswitch-based peptide structural differences for enhanced control over the particle catalytic properties.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.