The Structure of Collagen within Parchment - A Review
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_2_03_61_80.doc |
| Abstract: | SUMARRIES. For millennia parchment has been used as a writing material, commonly in the form of books, scrolls or folded sheets. Parchment is made from animal skins, predominantly from calf, sheep or goat. Parchment and skins have the characteristic molecular packing associated with other collagen rich structures such as tendon, aorta, bone and cornea. For medical purposes such tissues are usually analysed as close to the in vivo state as possible (hydrated and not degraded). This has allowed for a wealth of information to be elucidated concerning the structure of collagen and its hierarchical arrangements from the molecular structure to the fibrils to the organisation of fibres in a tissue. The main considerations in understanding the structure of parchment at the molecular level is that parchment exists in the dry state, and that it has been subjected to varying levels of deterioration brought about by external factors. This review centres on the structure of collagen within parchment. Discussed are the in vivo structure of collagen in skin, alterations to the structure of collagen and alterations to the hierarchical arrangement of collagen brought about by the parchment preparation process and deterioration of collagen structure that is associated with parchment degradation over time. CONCLUSION. In skin the molecular structure and hierarchical arrangement of collagen is reasonably well characterised. During the parchment preparation process, the regularity of this hierarchical arrangement is in part lost and the collagen becomes more disordered and undergoes a shortening of periodicity. The drying of the collagen plays a key role in this increased disorder. With parchment existing as a post-mortem tissue, the in vivo mechanisms of collagen turnover and repair are no longer present, and the collagen that is present at the time of animal slaughter is the collagen that will make up parchment. The deterioration of collagen is in part a co-operative process. With each deterioration event it becomes easier for further deteriorations to occur. From the starting point in parchment, where an element of architectural order is lost and conformational freedom is greater for the molecules, deterioration begins and allows more deterioration and less restriction of the molecules. Eventually, heavily deteriorated parchment will consist of collagen molecules that have been broken into many smaller peptides, undergone oxidative change, lost their triple helical structure and lost the hierarchical organisation that is characteristic of collagen. In this case the parchment is essentially consisting of gelatine and a mixture of polypeptides of varying length and stability. The detailed mechanisms of collagen degradation within parchment are relatively unclear. Understanding the deterioration of collagen and its causes in a conservation context will in future allow for greater care to be taken in damage assessment and preservation of parchments. |
|---|---|
| ISSN: | ISSN 0034-5806 |
