Is Supramolecular Organisation a Key Factor for Long Term Preservation ?
The long term alteration of organic archaeological materials often raises difficult questions concerning the preferential points of attack or “weakest points” of the material, and the subsequent chemical reactions leading to its transformation. These transformations are closely related to the archaeological context, and their study can shed new light on the history and significance of ancient objects. The stability of a solid organic material involves multiple attractive interactions between the constituent molecules. These interactions contribute to the internal cohesion of the material and are involved in chemical degradation processes. The branch of Chemistry studying molecular interactions is Supramolecular Chemistry, and we will examine in the present paper general principles applied to keratinised tissues (hair, skin, nail), a particular family of biological materials that often exhibit long-term preservation. A remarkable feature of these organic materials is the existence of precisely organised structures atseven successive length scalesranging from the atomic scale (diameter of a single keratin molecule: one nanometre) to the macroscopic scale (diameter of human hair: several tens of micrometers). In the present lecture we will try to answer the question: can the supramolecular organisation of such a complex material account for its long term preservation?
KeywordsSulphide Manganese Amide Cysteine Carboxyl
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