Cyclotriveratrylene (CTV) as a New Chiral Triacid Sacaffold Capable of Inducing Triple Helix Formation of Collagen Peptides Containing either a Native Sequence or Pro-Hyp-Gly Repeats

摘要

A new triacid scaffold is described based on the cone-shaped cyclotriveratrylene (CTV) molecule that facilitates the triple helical folding of peptides containing either a unique blood platelet binding collagen sequence or collagen peptides composed quence or collagen peptides composed of Pro-Hyp-Gly-OH. Peptides were coupled to this CTV scaffold and also coupled to the Kemp's triacid (KTA) scaffold. After assembly of peptide H-Gly-[PrO-Hyp-Gly]_2-Phe-Hyp-Gly-Glu(OAll)-Arg-Gly-Val-Glu(OAll)-Gly-[Pro-Hyp-Gly]_2-NH_2 (13) by an orthogonal synthesis strategy to both triacid sacffolds, followed by deprotection of the allyl groups, the molecular constructs spontaneously folded into a triple helical structure. In contrast, the non-assembled peptides did not. The melting temperature (T_m) of (+/-) CTV[CH_2C(O)N(H)Gly-[PrO-Hyp-Gly]_2-Phe-Hyp-Gly-Glu-Arg-Gly-Val-Glu-Gly-[Pro-Hyp-Gly]_2-NH_2]_3 (14) is 19 deg C, wherreas KTA[Gly-Gly-[Pro-Hyp-Gly]_2-Phe-Hyp-Gly-Glu-Arg-Gly-Val-Glu-Gly-[Pro-Hyp-Gly]_2-NH_2]_3 (15) has a T_m of 20 deg C. Thus, it was shown for the first time that scaffolds were also effectivein stabilizing the triple helix of native collagen sequences. The different stabilizing properties of the two CTV enantiomers could be measured after coupling of recemic CTV triacid to the collagen peptide, and subsequent chromatographic separation of the diastereomers. After assembly of the two chiral CTV scaffolds to the model peptide H-Gly-Gly-(Pro-Hyp-Gly)_5-NH_2 (24), the (+)-enantiomer of CTV 28b was found to serve as a better triple helix-inducing scaffold than the (-)-enantiomer 28a. In addition to an effect of the chirality of the CTV scaffold, a certain degree of flexibility between the two collagen mimics 20a and 20b, whereas the difference was only slight when two glycine residues were present between the CTV scaffold and the peptide sequence in collagen mimics 30a and 30b.