Interrogating Encapsulated Protein Structure within Metal-Organic Frameworks at Elevated Temperature.

Area of Science:

• Materials Science
• Biochemistry
• Structural Biology

Background:

• Metal-organic frameworks (MOFs) are hypothesized to enhance biomacromolecule stability.
• Direct evidence for the mechanism of MOF-mediated biomolecular stabilization is lacking.
• Bovine serum albumin (BSA) is a model protein often used to study denaturation.

Purpose of the Study:

• To develop and apply a novel analytical method to study the structure of encapsulated biomacromolecules.
• To provide direct evidence for the thermostabilization of BSA within MOFs.
• To investigate the structural integrity of BSA under thermal stress when confined within MOF matrices.

Main Methods:

• Utilized small-angle X-ray scattering (SAXS) to analyze BSA encapsulated in zeolitic imidazolate frameworks (ZIF-67 and ZIF-8).
• Employed spectral subtraction of the MOF (ZIF) from the biocomposite (BSA@ZIF) SAXS data.
• Applied Guinier, Kratky, and pair distance distribution function analyses to determine the radius of gyration and structural conformation of encapsulated BSA.

Main Results:

• In situ SAXS analysis demonstrated that BSA encapsulated within ZIF-8 and ZIF-67 retained its folded state and size at 70 °C.
• Native BSA, when exposed to 70 °C without encapsulation, showed signs of denaturation.
• The confinement within the ZIF scaffold effectively inhibited the unfolding and denaturation of BSA.

Conclusions:

• Entrapment within MOF cavities provides significant thermostability to encapsulated biomacromolecules like BSA.
• The novel SAXS analysis method offers valuable insights into biomolecular stabilization within MOFs.
• This approach may serve as a new technique for studying conformationally labile molecules in rigid matrices.