The results indicate that the fibrous keratin scaffold remains consistent between ethnic hair types. The hierarchies made by these may be modulated by variation in the content of keratin-associated proteins (KAPs) and lipids that alter the interfacial structures and lead to macroscopic differences in hair morphology.
This review discusses the need to understand the effects of relative humidity on parchment and the current understanding of parchment structure and hydration. It also provides a critical evaluation of the body of foregoing research investigating the effects of relative humidity on parchment artefacts. The critical evaluation shows that the current scientific evidence that can be used to inform the debate with regard to relative humidity guidelines for the preservation of parchment artefacts is insufficient, especially in the light of a greater understanding of parchment based documents when considered as composite materials comprising collagen and gelatine. The differential behaviour of collagen and gelatine (and consequently the effect on the interfaces between them) in terms of response to relative humidity changes, is proposed as a key factor to be considered for future studies. This review concludes with an analysis of the next steps required in parchment research in order to provide an informed advisory framework.
Developing a noninvasive method to assess the degraded state of historical parchments is essential to providing the best possible care for these documents. The conformational changes observed when collagen molecules, the primary constituent of parchment, unfold have been analyzed using attenuated total reflection-Fourier transform infrared (ATR-FT-IR) spectroscopy and the nanoscopic structural changes have been analyzed using X-ray diffraction (XRD). The relationship between the results obtained from these techniques was studied using principal component analysis, where correlation was found. The extent of gelatinization of historical parchments has been assessed using ATR-FT-IR and XRD and the frequency shifts observed as collagen degrades into gelatin have been reported. These results indicate that collagen degradation can be measured noninvasively in parchment and demonstrate the utility of ATR-FT-IR spectroscopy as a method to investigate historical documents.
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