School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
NSF's ChemMatCARS, Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States.
J Am Chem Soc. 2023 Apr 5;145(13):7323-7330. doi: 10.1021/jacs.2c13525. Epub 2023 Mar 24.
Encapsulating biomacromolecules within metal-organic frameworks (MOFs) can confer thermostability to entrapped guests. It has been hypothesized that the confinement of guest molecules within a rigid MOF scaffold results in heightened stability of the guests, but no direct evidence of this mechanism has been shown. Here, we present a novel analytical method using small-angle X-ray scattering (SAXS) to solve the structure of bovine serum albumin (BSA) while encapsulated within two zeolitic imidazolate frameworks (ZIF-67 and ZIF-8). Our approach comprises subtracting the scaled SAXS spectrum of the ZIF from that of the biocomposite BSA@ZIF to determine the radius of gyration of encapsulated BSA through Guinier, Kratky, and pair distance distribution function analyses. While native BSA exposed to 70 °C became denatured, in situ SAXS analysis showed that encapsulated BSA retained its size and folded state at 70 °C when encapsulated within a ZIF scaffold, suggesting that entrapment within MOF cavities inhibited protein unfolding and thus denaturation. This method of SAXS analysis not only provides insight into biomolecular stabilization in MOFs but may also offer a new approach to study the structure of other conformationally labile molecules in rigid matrices.
将生物大分子封装在金属有机骨架（MOFs）内可以赋予被包裹客体的热稳定性。人们假设，客体分子被限制在刚性 MOF 支架内会导致客体分子的稳定性提高，但尚未有直接证据证明这种机制。在这里，我们提出了一种使用小角 X 射线散射（SAXS）的新分析方法，以解决牛血清白蛋白（BSA）在两种沸石咪唑酯骨架（ZIF-67 和 ZIF-8）内封装时的结构。我们的方法包括从生物复合材料 BSA@ZIF 的 SAXS 谱中减去 ZIF 的比例谱，以通过 Guiner、Kratky 和对分布函数分析确定封装在 BSA 内的回转半径。当暴露于 70°C 的天然 BSA 变性时，原位 SAXS 分析表明，当封装在 ZIF 支架内时，封装的 BSA 在 70°C 下保留其大小和折叠状态，这表明 MOF 腔体内的包埋抑制了蛋白质的展开，从而抑制了变性。这种 SAXS 分析方法不仅提供了对 MOF 中生物分子稳定化的深入了解，而且还可能为在刚性基质中研究其他构象不稳定分子的结构提供新方法。
