Proteomic Characterization of Collagen-Based Animal Glues for Restoration

Animal glues are widely used in restoration as adhesives, binders, and consolidants for organic and inorganic materials. Their variable performances are intrinsically linked to the adhesive properties of collagen, which determine the chemical, physical, and mechanical properties of the glue. We have molecularly characterized the protein components of a range of homemade and commercial glues using mass spectrometry techniques. A shotgun proteomic analysis provided animal origin, even when blended, and allowed us to distinguish between hide and bone glue on the basis of the presence of collagen type III, which is abundant in connective skin/leather tissues and poorly synthetized in bones. Furthermore, chemical modifications, a consequence of the preparation protocols from the original animal tissue, were thoroughly evaluated. Deamidation, methionine oxidation, and backbone cleavage have been analyzed as major collagen modifications, demonstrating their variability among different glues and showing that, on average, bone glues are less deamidated than hide glues, but more fragmented, and mixed-collagen glues are overall less deamidated than pure glues. We believe that these data may be of general analytical interest in the characterization of collagen-based materials and may help restorers in the selection of the most appropriate materials to be used in conservation treatments.

Automated summary

Animal glues are commonly used in restoration, and their performance is determined by the adhesive properties of collagen. Mass spectrometry techniques were used to characterize the protein components of homemade and commercial glues. The study identified the animal origin of the glues and distinguished between hide and bone glue based on the presence of collagen type III. The analysis of chemical modifications showed variations among different glues. These findings have analytical significance in the characterization of collagen-based materials and can assist restorers in selecting appropriate materials for conservation treatments.