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Parchment - Ancient and Actual

archment has been used as a writing material from 100 - 200 A. D. (e.g. Dead Sea Scrolls) until the late Middle Ages, and manuscripts of parchment may be recognized among the most valuable objects of European cultural heritage. Parchment is the bearer of some of the most essential parts of early written history, which today still constitutes the foundation, in form of ideas, religion and policy, on which the modern European society is based. Large amounts of parchment manuscripts are stored in libraries and museums, where they gradually deteriorate. With the increasing air pollution the deterioration is severely accelerated, and within a few decades an enormous demand for conservation and restoration is expected. If this development has to be slowed down, extensive research in the deterioration has to be carried out in order to form the basis on which effective methods of conservation can be designed. A research group, with participants from Austria, Belgium, Denmark, England and France, has now been established to examine the deterioration of parchment. The examinations comprise not only the parchments itself but also the text and illustrations. Since the research is based on historical materials, the available sample sizes are very limited, and an important part of the project deals with the development of micro methods for the analysis of the state of deterioration. The research is partly supported by the European Union and partly by national sources.

Parchment mainly consists of the hide protein (collagen) matrix. The collagen molecule has a molecular weight around 350000 and consists of three peptide chains build from 18 different amino acids. Major parts of the chains are arranged as a triple helix held together by hydrogen bonds between the chains. Several triple helices are the bundled together to form fibres. It is believed that deterioration occurs by cleavage of the peptide chain at sensible positions, whereby the stability of the fibres decrease.

Department of Chemistry is involved in:

-Electron Paramagnetic Resonance Spectroscopy (EPR).
Cleavage of the peptide chain has, under certain conditions, been suspected to occur via formation of free radicals, which may be detected by EPR. Free radicals are detected, when parchment is exposed to SO2 polluted air, and the identity, behaviour and lifetime of the radicals may give a lead to where and how the cleavage takes place.

EPR-spectra of NO-radical detected in collagen.

- X-ray diffraction.
The fibres give distinct X-ray diffraction patterns dependent on the state of deterioration. This offers the opportunity to extract structural changes in the fibres due to deterioration.

- Hydrothermal stability measurement.
Cleavage of the peptide chains decrease the stability of the fibres. When heated in water the hydrogen bonds are destroyed, and the individual peptide chain curl up - the fibre shrinks. The temperature, at which this happens, is lower, the more deteriorated the material. The whole process is recorded on video, and digital image processing may then give information on the distribution of the state of deterioration. Photography of the fibre structure is shown on the right.

- Amino acid determination.
Oxidative degradation of collagen changes the amino acid composition. The determination of these small changes is complicated by the fact that glycine, the backbone of the triple helix, constitutes ~ 1/3 of the total number of amino acid. To obtain reliable results, a program, which model the full HPLC profile, is being developed.

Fragment of Dead Sea Scrolls.

"The Lindisfarne Gospels", Copyright 1997, The British Library Board British Library Cotton Nero D. IV.

Fiber structure:
Methods :

-X-ray Diffraction.
-Hydrothermal Stability Measurements.
-Amino Acid Determination.

Click X-ray picture for full size image.

Animated gif of shrinking collagen fibres.

HPLC-chromatogram of collagen.

Links :

HPLC-Wizard, a Program to model HPLC profiles
Homepage of Structural Chemistry Group
Homepage of Department of Chemistry