彩绘文物中蛋白类混合胶料的相互作用与稳定性研究

Study on the Interaction and Stability of Mixed Proteinaceous Binders in Polychrome Relics

皮胶、蛋类和奶类作为彩绘文物中常见的胶结材料,在我国古代存在混合使用的工艺。为探究这类混合胶料体系内部各组分的相互作用与其在光热老化条件下的稳定性,深入了解彩绘文物的劣化机理,使用扫描电子显微镜、傅里叶红外光谱仪以及热重-差示扫描量热仪等分析方法,对鸡蛋-皮胶、牛奶-皮胶与牛奶-鸡蛋三种混合胶料的稳定性与蛋白质二级结构进行了表征。结果表明,以上胶料经过混合后,热稳定性与光稳定性相较单一胶料均显著升高。红外光谱显示,样品经过老化之后谱峰加宽,波数范围位于1600~1700 cm^(-1)之间的蛋白质特征谱带酰胺Ⅰ带向低波数方向移动。酰胺Ⅰ带高斯拟合结果显示,随着混合比例的变化,混合胶料中有序结构的含量呈现出先升后降的趋势,在有序结构含量最高的样品中,无规卷曲结构含量也达到较低的水平。同时,鸡蛋-皮胶的混合比例介于1∶1~1∶2之间时,有序结构的含量高于任意单一胶料,最高可达64.87%,其稳定性最强。经过老化的胶料蛋白质二级结构含量均发生变化,有序的α-螺旋结构整体呈现下降趋势,无规卷曲结构则明显上升,而几种混合胶料α-螺旋结构的含量依旧高于单一胶料,可见混合胶料具有更强的稳定性。热重分析结果同样表明,老化前后混合胶料的热稳定性均高于单一胶料,推测是因为混合体系中蛋白质与蛋类、奶类中的脂质相结合,蛋白质与脂质的相互作用进一步促进了蛋白质结构稳定性的提升。本研究从稳定性的角度分析了彩绘文物中的混合胶料,为研究古代胶料的老化机理和保护方法提供了参考。

Animal glue,eggs,and milk were often mixed in ancient China as cementitious materials in painted cultural relics.To explore the interaction of mixed binders and the stability under light aging conditions,to understand the deterioration mechanism of polychrome relics,the stability and protein secondary structure of egg-animal glue,milk-animal glue,and milk-egg mixed binders were characterized by Scanning electron microscopy,FTIR and TG analysis.The results showed that after mixing,the above binders'thermal stability and light stability were significantly increased.The infrared spectrum results show that spectral peak broadening after aging of the sample,and the amideⅠband of the protein characteristic spectrum with a wavenumber range between 1600~1700 cm^(-1)shifts towards the wavenumber direction.The Gaussian fitting results of the amideⅠband show that with the change of mixing ratio,the content of ordered structure in the mixed binders shows a trend of first increasing and then decreasing.In the samples with the highest ordered structure content,the random curl structure content also reaches a lower level.At the same time,when the mixing ratio of egg and animal glue is between 1∶1 and 1∶2,the content of the ordered structure is higher than any single binders,with a maximum content of 64.87%,indicating its strongest stability.The content of the secondary structure of protein in the aged binders has changed.The α-helix structure shows a downward trend,while the random curl structure shows a significant increase.The α-helix structure in several mixed binders is still higher than that of a single binder material,indicating that the mixed binders have a certain degree of stability.The results of Thermogravimetric analysis also showed that the thermal stability of the mixed binders before and after aging was higher than that of the single binders,presumably because the protein in the mixed system combined with the lipid in eggs and milk and the interaction between protein and lipid further promoted the stretching and rearrangement of protein molecular structure,which improved the stability.From the stability perspective,the reason for the mixed-use of adhesive materials in painted cultural relics was explained,providing a reference for studying ancient adhesive materials'aging mechanism and protection methods.