Facile Fabrication of Protein-Macrocycle Frameworks

Area of Science:

• Materials Science
• Biochemistry
• Crystallography

Background:

• Engineered protein assembly is crucial for developing functional materials.
• Anionic calixarenes serve as scaffolds to induce protein oligomerization and assembly.
• Protein-calixarene composites offer new avenues for materials design.

Purpose of the Study:

• To investigate the cocrystallization of sulfonato-calix[8]arene (sclx) with the protein RSL.
• To characterize the resulting protein-calixarene composites and their structural properties.
• To explore the potential of these composites in functional materials and structure determination.

Main Methods:

• Cocrystallization of RSL protein with sulfonato-calix[8]arene across a range of pH conditions.
• Analysis of crystal structures to determine framework architecture and protein encapsulation.
• Nuclear Magnetic Resonance (NMR) experiments to study macrocycle-modulated pKa values and assembly mechanisms.

Main Results:

• Three crystal forms were obtained, with two types of porous frameworks exhibiting pore diameters greater than 3 nm.
• Protein encapsulation within the calixarene frameworks was confirmed, with proteins acting as nodes in octahedral coordination.
• Rapid formation of millimeter-scale crystals was achieved under specific conditions, and de novo structure determination was enabled by sclx.

Conclusions:

• Sulfonato-calix[8]arene effectively induces the assembly of RSL protein into ordered, porous frameworks.
• These protein-calixarene composites demonstrate potential for creating novel functional materials.
• The study highlights the utility of calixarene-protein interactions for both framework fabrication and protein structure analysis.