PubMed · 13088877
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C J MARTIN, A E AXELROD. 1953. A modified method for determination of hydroxyproline.. https://doi.org/10.3181/00379727-83-20386
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The aim of this study was to synthesize on a larger scale, an experimental polyamide based on an amino acid of trans-4-hydroxy-L-proline. The polyamide of trans-4-hydroxy-L-proline has been used as porogen filler (i.e., a hydrophilic pore generating material) in nondegradable acrylic bone cement. In in vitro studies, this hydrophilic filling component has been shown to form porosity within the acrylic bone cement in an aqueous environment. The formation of in situ porosity in the acrylic polymer matrix is believed to improve the fixation between the cement and the living bone. Namely, a porous structure can support bone ingrowth and strengthen the mechanical connection between the acrylic bone cement and the bone. The monomer, trans-4-hydroxy-L-proline methyl ester, was prepared from trans-4-hydroxy-L-proline by means of two steps, and the monomer was then polymerized to polyamide of trans-4-hydroxy-L-proline. The polymerization was carried out using a melt polycondensation method. The molecular weights (M(psi)) of the produced polyamides were between 1800 and 3600. The products were characterized by FTIR and (1)H-NMR spectroscopy.
Conformational analysis of peptides containing cis-3-hydroxy-d-proline (d-cis-3-Hyp) by NMR studies revealed that the 3-hydroxyl group in this amino acid plays a significant role in the overall three-dimensional structures of the peptides. When the d-cis-3-Hyp had its 3-hydroxyl group protected as the benzyl (Bn) ether, the peptide displayed a beta-hairpin structure in both CDCl(3) and DMSO-d(6). Even after the removal of the Bn group, the resulting deprotected compound retained the same structure as in the protected version in CDCl(3). However, in polar solvent DMSO-d(6), the C-terminal strand of the hydroxyl-deprotected peptide flipped to the side of the hydroxyl group, breaking the hairpin to form a pseudo beta-turn-like nine-membered ring structure involving an intramolecular hydrogen bond between LeuNH --> HypC3-OH.
AIM: To study the chemical constituents of the stems of Opuntia vulgaris Mill(Cactaceae). METHODS: The compounds of Opuntia vulgaris were isolated by chromatography of Amberlite Dowex 50 and silica gel, and identified by means of UV, IR, MS, 1D and 2D NMR. RESULTS: Three compounds were isolated and identified as: opuntin B(I), 4-hydroxyproline(II) and tyrosine(III). CONCLUSION: Compound I is a new alkaloid.