Magnetically Directed Two-Dimensional Crystallization of OmpF Membrane Proteins in Block Copolymers

Area of Science:

• Biophysics
• Structural Biology
• Materials Science

Background:

• Two-dimensional (2D) crystallization of membrane proteins (MPs) is crucial for structural determination, drug design, and biomimetic applications.
• Fabricating large, ordered MP 2D crystals within block copolymer (BCP) matrices remains a significant challenge.
• A scalable method for aligning and crystallizing MPs in thin films is needed for broader applications.

Purpose of the Study:

• To introduce and validate a novel method for growing larger and more ordered 2D membrane protein crystals.
• To investigate the effect of a strong magnetic field on MP crystallization in thin-film geometries.

Main Methods:

• Utilized a strong magnetic field during the crystallization process of membrane proteins.
• Employed outer membrane protein F (OmpF), a beta-barrel MP, within polybutadiene-poly(ethylene oxide) (PB-PEO) block copolymer membranes.
• Analyzed crystal size and order using negative-stain electron microscopy (EM) and cryo-electron microscopy (cryo-EM) with Fourier transform signal-to-noise (SNR) analysis.

Main Results:

• Crystals grown in the magnetic field were up to 5 times larger than those grown conventionally.
• Fourier transform analysis revealed twice as many high-SNR diffraction peaks in magnetically grown crystals, indicating improved order.
• Demonstrated enhanced crystal size and order for OmpF in PB-PEO membranes.

Conclusions:

• A strong magnetic field is an effective tool for enhancing the size and order of 2D membrane protein crystals.
• This technique offers a facile and scalable approach for fabricating high-quality MP 2D crystals.
• The magnetic field-assisted method holds promise for advancing structural biology and biomimetic device development.