Ring-Opening Polymerization of Hemoglobin

Hemoglobin (Hb), an oxygen-carrying protein, has an α2β2 tetrameric structure that dissociates reversibly into two αβ dimers (α2β2 ⇄ 2αβ). We synthesized a cyclic Hb-ring monomer with two β subunits bound through a 10 kDa polyethylene glycol (PEG) chain. The monomer induced ring-opening polymerizati...

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Bibliographic Details
Published in:Biomacromolecules 2019-04, Vol.20 (4), p.1592-1602
Main Authors: Matsuhira, Takashi, Yamamoto, Keizo, Sakai, Hiromi
Format: Article
Language:English
Subjects:
Hemoglobins - chemistry
Humans
Polyethylene Glycols - chemistry
Polymerization
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Summary:Hemoglobin (Hb), an oxygen-carrying protein, has an α2β2 tetrameric structure that dissociates reversibly into two αβ dimers (α2β2 ⇄ 2αβ). We synthesized a cyclic Hb-ring monomer with two β subunits bound through a 10 kDa polyethylene glycol (PEG) chain. The monomer induced ring-opening polymerization to produce a supramolecular polymer via intersubunit interaction of αβ dimers of an Hb molecule at the PEG terminals. Both the ring-closed monomer and the ring-opened supramolecular polymer were then fixed covalently by intramolecular cross-linking of two β subunits. Quantification of fixed products at various monomer concentrations revealed the equilibrium constant (K), a ratio of propagation and depropagation rate constants, as 5.68 mM–1. The average degree of polymerization ( DP ̅ ) increased proportionally, concomitantly with the initial monomer concentration. Hb polymer with DP ̅ = 13.2 (M n = ca. 1 MDa) was obtained by cross-linking at 2.33 mM. Our novel strategy of ring-opening polymerization of Hb will eventually realize a highly aligned and efficiently polymerized Hb for creating artificial oxygen carriers for a clinical use.
ISSN:1525-7797
1526-4602
DOI:10.1021/acs.biomac.8b01789