Abstract
Pro–Hyp–Gly is a characteristic amino acid sequence found in fibrous collagens, and (Pro–Hyp–Gly)~10~, which has been widely used as a collagen‐model peptide, forms a stable triple‐helical structure. Here, we synthesized polypeptides consisting of the Pro–Hyp–Gly sequence by direct polycondensation of (Pro–Hyp–Gly)~n~, where n = 1, 5, and 10, using 1‐hydroxybenzotriazole and 1‐ethyl‐3‐(3‐dimethyl‐aminopropyl)‐carbodiimide hydrochloride in both phosphate buffer (pH = 7.4) and dimethylsulfoxide (DMSO) solutions for 48 h at 20°C. The reaction of (Pro–Hyp–Gly)~5~ and (Pro–Hyp–Gly)~10~ in DMSO successfully gave polypeptides with molecular weights over 10,000, whereas low molecular weight products were obtained by reaction in phosphate buffer (pH = 7.4). In contrast, Pro–Hyp–Gly at a concentration of 50 mg/mL in phosphate buffer (pH = 7.4) gave polypeptides with molecular weights over 10,000. The Fourier transform infrared (FTIR) and ^1^H nuclear magnetic resonance (NMR) spectra of poly(Pro–Hyp–Gly)~10~ revealed that the polymerization of (Pro–Hyp–Gly)~10~ described in this report had no side reactions. Each polypeptide obtained shows a collagen‐like triple‐helical structure, and the triple‐helical structures of poly(Pro–Hyp–Gly) and poly(Pro–Hyp–Gly)~10~ were stable up to T = 80°C, which suggests that the high molecular weight promotes stability of the triple‐helical structure, in addition to the high Hyp content. Furthermore, transmission electron microscopy (TEM) observations show that poly(Pro–Hyp–Gly)~10~ aggregates to form nanofiber‐like structures about 10 nm in width, which suggests that a Pro–Hyp–Gly repeating sequence contains enough information for triple‐helix formation, and for subsequent nanofiber‐like structure formation. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 163–172, 2005
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