Ring-Opening Polymerization of Hemoglobin

Area of Science:

• Biochemistry
• Polymer Chemistry
• Biomaterials Science

Background:

• Hemoglobin (Hb) is an oxygen-carrying protein with a tetrameric structure (α2β2) that reversibly dissociates into dimers (αβ).
• Developing efficient artificial oxygen carriers is crucial for clinical applications.

Purpose of the Study:

• To synthesize a cyclic hemoglobin monomer capable of ring-opening polymerization.
• To create a supramolecular polymer of hemoglobin with potential for use as an artificial oxygen carrier.

Main Methods:

• Synthesis of a cyclic Hb monomer using a polyethylene glycol (PEG) linker between β subunits.
• Induction of ring-opening polymerization via intersubunit interactions of Hb dimers.
• Covalent fixation of the resulting supramolecular polymer through intramolecular cross-linking.
• Quantification of polymerization equilibrium and degree of polymerization.

Main Results:

• A cyclic Hb monomer was successfully synthesized and induced ring-opening polymerization.
• The equilibrium constant (K) for polymerization was determined to be 5.68 mM⁻¹.
• A hemoglobin polymer with an average degree of polymerization of 13.2 (Mn ≈ 1 MDa) was achieved.

Conclusions:

• A novel strategy for ring-opening polymerization of hemoglobin was established.
• This method allows for the creation of highly aligned and efficiently polymerized Hb.
• The developed Hb polymers hold promise for the development of clinical artificial oxygen carriers.