胶原是广泛研究和应用的生物材料, 具有独特的三螺旋结构, 此结构与其生物学性能密切相关。 以胶原模拟多肽(collagen mimetic peptide, CMP) 作为胶原的模型分子, 通过圆二色谱研究了CMP的三螺旋结构、 热稳定性等随序列或长度的改变所发生的规律性变化。 根据形成胶原三螺旋结构的重复序列(POG)n及胶原上α2β1整合素识别位点序列GFOGER设计五种不同序列或长度的CMP, 采用圆二色谱表征了CMP的三螺旋结构, 并通过检测CMP的程序升温变性和程序降温复性过程中圆二色谱的变化, 研究了CMP三螺旋结构的热变性过程、 解链温度以及复性过程。 实验结果显示, 五种CMP室温下均以三螺旋结构的形式存在, CMP三螺旋结构的热稳定性随POG的个数增加而增强; 不同于胶原, CMP三螺旋结构的热变性是可逆的, 升温过程中三螺旋解聚(变性), 降温过程又可重新组装(复性), 复性过程有明显的“磁滞”现象。 研究结果可为进一步研究胶原与CMP分子特征性的三螺旋结构形成规律以及基于CMP的人工类胶原生物材料的研究提供依据。

In the present study, the authors explore the triple-helix conformation and thermal stability of collagen mimetic peptides (CMPs) as a function of peptide sequence and/or chain length by circular dichroism(CD). Five CMPs were designed and synthetized varying the number of POG triplets or incorporating an integrin α2β1 binding motif Gly-Phe-Hyp-Gly-Glu-Arg (GFOGER). CD spectroscopy from 260 to 190 nm was recorded to confirm the existence of triple-helix conformation at room temperature, while thermal melting and thermal annealing of triple-helix (thermal unfolding and refolding of triple-helix, respectively) was characterized by monitoring ellipticity at 225 nm as a function of temperature. The results demonstrated that all the CMPs adopted triple-helix conformation, and the thermal stability of the CMPs was enhanced with increasing the number of POG triplets. In contrast to natural collagen, the thermal denaturation processes of CMPs were reversible, i.e. the triple-helix unfolded upon heating while refolded upon cooling. Meanwhile, the phenomenon of “hysteresis” was observed by comparing melting and thermal curves. These findings add new insights to the mechanisms of collagen and CMPs assembly, as well as provide an alternative approach to the fabrication of artificial collagen-likes biomaterials.