Eureka!

Have just posted this to Dan Porter’s shroudstory.com site:

October 31, 2013 at 3:46 am | #52

Stop press:  Forget about the primary cell wall, forget about hemicelluloses!  They may be relevant to cotton, but not linen (maybe retting removes them at the same time as pectins).

Fact: one can dunk linen in undiluted oven cleaner (“5-15% sodium hydroxide”) for several hours and it has scarcely any effect on its ability to take a scorch (whereas that of cotton is clobbered by the same treatment).

Why? The answer has been staring me in the face for months, but I’m either too thick or senile or both to have seen it.   Dislocation nodes.

So how did the eureka moment arrive? I began wondering what might be taking the faint scorch on linen if it was not hemicellulose. Fats or protein? They would surely be clobbered with strong alkali. Lignin (mentioned yesterday)? I steeped linen yesterday in strong metabisulphite solution, said to dissolve lignin, but there was no effect on “scorchability”. So what does that leave?

Answer – amorphous cellulose, i.e. cellulose that is NOT part of highly crystalline arrays. That is a description of cellulose in the PCW and perhaps a few regions of the SCW also, and importantly, while more ready to dehydrate and scorch, it may still be chemically resistant to alkali.

Then I suddenly remembered a posting I did months ago: linen fibre nodes are where one sees most of the colour in the scorched fabric under the microscope.

https://shroudofturinwithoutallthehype.wordpress.com/2013/01/08/it-would-seem-that-those-linen-fibre-nodes-aka-dislocations-are-prime-targets-for-a-thermal-imprint-from-a-hot-template-scorch-mark/

Scorched linen fibre - note the concentration of colour at the nodes.

Scorched linen fibre – note the concentration of colour at the nodes.

Somewhere I’ve read that odd things happen to cellulose in the region of flax nodes (reversal of helical direction?).

Hypothesis: the dislocation nodes of linen fibres have relatively non-crystalline cellulose, and it is that which is the main site of chemical dehydration in a retted flax fibre that has lost most of its PCW hemicellulose through microbial action.

Does anyone have any good HD photomicrographs of Shroud image-bearing fibres that show the nodes?

Preliminary search for supporting  literature:

“Changes observed on thermal ageing of flax in air at 190  consistent with oxidation of amorphous cellulose and formation of carbonyl and carboxylate moieties; the non-dichroic nature of the carbonyl band confirms that the ordered crystalline regions were not primarily involved.”

Garside, Paul and Wyeth, Paul (2004) Polarised ATR-FTIR characterisation of cellulosic fibres in relation to historic artefacts. Restaurator, 25, (4), 249-259.

http://eprints.soton.ac.uk/15328/

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See also the first page of pdf (rest behind paywall) with reference to amorphous cellulose from:

Cellulose

February 2011, Volume 18, Issue 1, pp 17-31
Thermogravimetric measurement of amorphous cellulose content in flax fibre and flax pulp

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Dislocations in plant fibres and in Turin Shroud fibres

L.G. Thygesen

Proceedings of the International Workshop on the Scientific approach to the Acheiropoietos Images,  ENEA Frascati, Italy, 4‐6 May 2010

http://www.acheiropoietos.info/proceedings/ThygesenWeb.pdf

“The exact structure and composition of dislocations remains unknown. They are assumed  to contain mainly cellulose, lignin and hemicellulose like the rest of the secondary cell wall. Traditionally dislocations are  considered to contain amorphous cellulose in contrast to the surrounding cell wall, which contains crystalline  cellulose. However, recent results indicate that this assumption is not correct as dislocations are birefringent just like the bulk cell wall [3], which indicates that the structure is not amorphous. By applying tensile load in the longitudinal direction of individual fibres, dislocations may be stretched and thus aligned with the cellulose  microfibrils of the surrounding bulk cell wall [4], at least under some circumstances. This result indicates that the  cellulose micro fibrils continue through the dislocations,  i.e. dislocations may have a less ‘ordered’ and/or a more ‘loose’ structure, but they are not places where microfibrils are discontinuous.”

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“The cross markings, known as nodes, on flax fibres give them their characteristics microscopic appearance. There may be up to 800 nodes in a single flax fibre cell. Nodes are fissures in the cell walls and indicate a change in the spiral direction of the fibrils which constitute cell walls. Spiralling imparts strength to the cell and hence, to the flax fibre. The polygonal cross section of the flax fibre cell is typical of most plant cells.”

  Ritu Pandey (2009)

http://agropedia.iitk.ac.in/content/etymology-flax

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About Colin Berry

Retired science bod, previous research interests: phototherapy of neonatal jaundice, membrane influences on microsomal UDP-glucuronyltransferase, defective bilirubin and xenobiotic conjugation and hepatic excretion, dietary fibre and resistant starch.
This entry was posted in Shroud of Turin and tagged , , , , , , . Bookmark the permalink.

2 Responses to Eureka!

  1. colinsberry says:

    Test insert image into comments

    “compare

  2. colinsberry says:

    Second test, reduced dimensions

    “compare

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