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交联剂可以明显提高以胶原基生物材料的物理性能。在皮革生产中,噁唑烷是一种常用的醛类鞣剂,但其与皮胶原交联的机理有待进一步研究。噁唑烷与植物单宁结合鞣时,噁唑烷通过开环形成了碳正离子中间体,之后进一步与胶原氨基酸的侧链氨基及植物单宁的黄酮环反应。本实验中,我们对噁唑烷与胶原的反应进行了一系列的分析研究。对经噁唑烷鞣制的胶原进行高效液相色谱分析后发现,噁唑烷与酪氨酸侧链发生了不可逆反应。质谱分析证明噁唑烷与赖氨酸残基形成了席夫碱化合物,这是一个可逆反应。在NaCNBH3存在下,将一个模型多肽链Suc-Ala-Phe-Lys-AMC与噁唑烷反应并进行质谱分析,发现生成的产物相对分子质量增加了28 kD,这是由于赖氨酸上增加了两个甲基基团。差示扫描量热分析发现,在结合鞣中先加入植物单宁再加入噁唑烷鞣剂会得到更好的协同效应。胶原与反应活性较强的噁唑烷A反应后的圆二色谱分析显示椭圆率下降,这是由于胶原分子发生聚集而非二级结构的改变。基于获得的分析结果,提出了一个噁唑烷与胶原氨基酸侧链反应的机理模式。
Crosslinkers can significantly improve the physical properties of collagen-based biomaterials. In leather production, oxazolidine is a commonly used aldehyde tanning agent, but its mechanism of cross-linking with dermal collagen remains to be further studied. Oxazolidine tanning with plant tannins, the oxazolidine ring opened by the formation of a carbonium ion intermediate, and then further with the collagen amino acid side chain and plant tannin flavonoid ring reaction. In this experiment, we conducted a series of analytical studies on the reaction of oxazolidine with collagen. The oxazolidine-tanned collagen was analyzed by high performance liquid chromatography and found that the oxazolidine and tyrosine side chains irreversibly reacted. MS analysis confirmed that the oxazolidine and lysine residues formed a Schiff base compound, which is a reversible reaction. In the presence of NaCNBH3, a model polypeptide chain, Suc-Ala-Phe-Lys-AMC, was reacted with oxazolidine and subjected to mass spectrometry to find that the relative molecular mass of the resulting product was increased by 28 kD due to an increase in lysine Two methyl groups. Differential scanning calorimetry analysis found that adding tannin in combination with tannin followed by oxazolidine tanning agent yielded better synergistic effect. Circular dichroism analysis of the collagen with the more reactive oxazolidine A reaction showed a decrease in ellipticity due to the aggregation of collagen molecules rather than secondary structure changes. Based on the analytical results obtained, a mechanism model for the side chain reaction of oxazolidine with collagen amino acids was proposed.