Laboratorium für Organische Chemie, ETH Zürich , D-CHAB, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland.
Laboratorium für Physikalische Chemie, ETH Zürich , D-CHAB, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.
J Am Chem Soc. 2017 Sep 13;139(36):12815-12820. doi: 10.1021/jacs.7b07498. Epub 2017 Sep 5.
Covalent cross-links are crucial for the folding and stability of triple-helical collagen, the most abundant protein in nature. Cross-linking is also an attractive strategy for the development of synthetic collagen-based biocompatible materials. Nature uses interchain disulfide bridges to stabilize collagen trimers. However, their implementation into synthetic collagen is difficult and requires the replacement of the canonical amino acids (4R)-hydroxyproline and proline by cysteine or homocysteine, which reduces the preorganization and thereby stability of collagen triple helices. We therefore explored alternative covalent cross-links that allow for connecting triple-helical collagen via proline residues. Here, we present collagen model peptides that are cross-linked by oxime bonds between 4-aminooxyproline (Aop) and 4-oxoacetamidoproline placed in coplanar Xaa and Yaa positions of neighboring strands. The covalently connected strands folded into hyperstable collagen triple helices (T ≈ 80 °C). The design of the cross-links was guided by an analysis of the conformational properties of Aop, studies on the stability and functionalization of Aop-containing collagen triple helices, and molecular dynamics simulations. The studies also show that the aminooxy group exerts a stereoelectronic effect comparable to fluorine and introduce oxime ligation as a tool for the functionalization of synthetic collagen.
共价交联对于三螺旋胶原的折叠和稳定性至关重要，三螺旋胶原是自然界中最丰富的蛋白质。交联也是开发合成胶原基生物相容性材料的一种有吸引力的策略。自然界利用链间二硫键来稳定胶原三聚体。然而，将其引入合成胶原很困难，需要用半胱氨酸或同型半胱氨酸替代典型的氨基酸（4R）-羟脯氨酸和脯氨酸，这会降低胶原三螺旋的预组织化程度，从而降低其稳定性。因此，我们探索了通过脯氨酸残基连接三螺旋胶原的替代共价交联。在这里，我们介绍了通过 4-氨基氧基脯氨酸（Aop）和 4-氧代乙酰氨基脯氨酸之间肟键交联的胶原模型肽，这些脯氨酸残基位于相邻链的 Xaa 和 Yaa 位置。共价连接的链折叠成超稳定的胶原三螺旋（T ≈ 80°C）。交联的设计是通过对 Aop 构象性质的分析、对含有 Aop 的胶原三螺旋稳定性和功能化的研究以及分子动力学模拟来指导的。这些研究还表明，氨基氧基基团具有与氟相当的立体电子效应，并引入肟键合作为合成胶原功能化的工具。
