Random and Sequential Copolypeptides Containing O-Phospho-L-Threonine and L-Aspartic Acid; Roles in CaCO3 Biomineralization
✍ Scribed by Shinya Hayashi; Kousaku Ohkawa; Hiroyuki Yamamoto
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 275 KB
- Volume
- 6
- Category
- Article
- ISSN
- 1616-5187
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✦ Synopsis
Abstract
Summary: The present study describes the synthesis of novel polypeptides containing O‐phospho‐L‐threonine [Thr(PO~3~H~2~)] and L‐aspartic acid. Random copolypeptides copoly[Thr(PO~3~H~2~)^X^Asp^Y^] (X:Y = 25:75, 50:50, 75:25), were conventionally prepared by copolymerization of Thr(PO~3~Ph~2~) N‐carboxyanhydride (NCA) and Asp(OBzl) NCA followed by deprotection of the phenyl and benzyl groups by catalytic hydrogenolysis over PtO~2~. Polycondensation of the protected peptide p‐nitrophenyl esters [Thr(PO~3~Ph~2~)]~Z~‐Asp(OBzl)‐ONp and subsequent deprotection yielded the sequential polypeptides poly[Thr(PO~3~H~2~)~Z~‐Asp] (Z = 1–4). By using the synthetic polypeptides, their effects on the growth of CaCO~3~ crystals were examined. In the poly[Thr(PO~3~H~2~)~Z~‐Asp]/CaCO~3~ systems, brushlike calcite and spherical vaterite were formed, with the former being found at [Ca^2+^]/[Res] ratios of ≥180, ≥140, ≥120, and ≥100 for Z = 1, 2, 3, and 4, respectively. These results indicate that an increase of Thr(PO~3~H~2~) residues in the repetitive unit induces the characteristic brushlike calcite, a fact indicating that Thr(PO~3~H~2~) residues can modify the CaCO~3~ crystal morphology.
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