h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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Leather has been processed to reduce its biodegradability. This also makes it tougher. However, it occurs to me that there might be another way of making a very skin-like material which was non-biodegradable for a different reason and also softer and more elastic.
Leather is presumably made of something
like a mat of keratin and collagen, i.e. two fibrous proteins with other components of skin removed, and then of course tanned and otherwise treated with various substances to remove fats, water, elastin and so forth.
My idea is to take the D-forms of amino acids, i.e. ones which are not so common in biochemistry, and produce three protein-like polymers, similar to but simpler than collagen, keratin and elastin. The keratin-like polymer consists of seven-segment units where the first and fourth units are D-alanine separated by alternate two and three units of some other D- amino acid, which mimics the structure of alpha-keratin. These are arrangeable in helices of several orders - i.e. there is a helix of this polymer which is then twisted together with another similar helix, those two filaments are twisted together and these altogether form a quadruple helix, which would be left-handed. This substance itself could form a useful horn-like, i.e. plastic-like, polymer which could replace wool, be used for wigs or be made into sheets or more bulky items as a kind of plastic.
The next polymer is the collagen-like one. This consists of a triple helix made up of D-proline and modified hydroxylated prolines and lysines. Then there's a problem: collagen is largely glycine, which is not chiral. I suggest getting round this problem by synthesising a modified glycine where one or both of the hydrogens off the carbon is replaced by fluorine and/or chlorine. Fibres of these ought to form into a triple helix, with the unfortunate complication that i have no idea what the halogenation would do - i'm just blindly hoping that it would sort of make the glyciny stuff behave like real glycine without being metabolisable. This collageny stuff could be added to calcium phosphate or other things to make it more resilient to strain, just as it is in bones and teeth.
There also needs to be some kind of non-biodegradable elastane, of which there are plenty of examples, for instance neoprene.
How to make the stuff? Well, assemble all the necessary info on strands of mRNA, make artificial ribosomes and tRNA, all the necessary machinery to keep that lot going and well, to be honest, probably sit in a corner and cry because it's probably going to be impossible. Anyway, once you've done that bit you're going to have two almost non-biodegradable fibrous proteins which can either be used separately as if they're synthetic fibres to replace wool, hair and horn, and put together in some kind of mat with the elastane and combined with a bit of water and maybe silicone oil, might, _might_, just produce an artificial skin-like substance suitable for clothing and maybe as a dressing for wounds.
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[+] although the //sit in the corner and cry// outcome seems
highly probable. |
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But I wonder if the useful properties of
leather don't derive as much from microstructure as from
chemical composition. Which would require rather more
elaborate genetic engineering of entire cells, including cell-
cell interactions (effectively, artificial life at the level of
entire organs, even more ambitious than whole cells). |
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Yes, that's something i worry about too but considering how seriously messed about with leather is in its manufacture i wonder if it really is. I suspect a lot of the delicate structures of the hide must be lost in that process. |
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Why do you think that more expensive, less industrially processed, vegetable tanned leathers are preferred for high-end work? |
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As opposed vera pelle sinistra? |
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Everything sounds good up to the last paragraph. Then you are just throw the idea into a black box and shouting "work!". This all seems like a complicated "we can do this without cells!" which even a cursory glance at your methods reveals "no we cant!". Either you need a sequenced process that assembles the substrates while avoiding the inevitable chemical and physical conflicts or producing a purified final product or you need to admit that you really need the complicated structure of cells and a tissue to make this possible and then its the wonderful world of gen-mod protein expression. You could spend the rest of your life on just one step. |
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Oh dear oh dear. I hope you have a nice corner. |
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[mouse] is right, in that the toughness of leather depends
a lot on the arrangement of the proteins, at all levels of
scale. |
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On the other hand, you could probably develop a process
for spinning your right-handed proteins into a structure
which would be quite leatherish, so maybe this is soluble. |
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On the other hand, making the proteins in the first place is
going to be a complete nightmare. Even persuading
bacteria or algae or yeast or cell-free systems to make
normal collagen and keratin in viable amounts is jolly
tricky. But in your case, you first have to make the right-
handed ribosomes. |
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A ribosome is a machine made of N proteins (where I don't
remember N, but it's probably about 10-50) and M rRNAs
(where M is between a few and 10), so you're going to have
to make all these. Plus protein synthesis needs tRNAs,
plus enzymes to link each amino acid to its corresponding
tRNA, plus a whole bunch of ancillary factors. And the only
way to make all these things is by using a set of right-
handed cellular machinery, which needs... |
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So, you really need to make right-handed bacteria as a
starting point (so that the whole damned thing replicates
and you don't have to keep making right-handed
machines). You're going to have to feed it with left-
handed sugars and stuff, but hey. |
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(Oh, and if these weird bugs get out of the lab and feel
hungry, guess what they're going to want to eat?) |
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It's probably going to be cheaper and faster to find a
planet where the residents are all right-handed (we should
have a 50:50 chance). We can then skin them for their
non-biodegradable hides, and they can do the same to us. |
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On the other hand, why bother? I'm pretty sure you could
make polymers with subunits analogous to amino acids (in
fact there are some), and polymerize these in a
respectable way, and then co-precipitate and spin and
weave them
into matted fibres which would be very leathery. There
are
already half-passable synthetic leathers and, if people
were prepared to pay, there'd probably be better ones. |
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On yet another hand, how many leather things do you own
that have rotted? And how many that have worn out, or
have dried out and cracked (which your mirrorleather will
do)? |
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On the final hand, exactly what properties of real leather
do you want to replicate, non-biodegradably? |
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But I find myself unexpectedly with one more hand, with
which to proffer this bun [+] for an interesting if totally
impracticable idea. |
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more of a concept than an idea... [+] anyways. |
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I was assuming that the "right handedness" was to indicate inaptness or artificiality but my impression may be skewed due to my personal left handedness. |
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/Then you are just throw the idea into a black box and shouting "work!"./ |
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I recommend adding "Damn you!" |
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One could come up with some sort of punishment for the units where no useful work was being done, for example the autoclave. This then becomes directed evolutionary magic. Apropos this I would point out that "cant" qua "sing" is the root of "incantation" and probably "chant". Those two and a tall peaked hat with a helix on it ought to get you rolling. |
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Halogenated glycine polymers seems like it might not be too hard. |
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To follow up on [MaxwellBuchanan]'s earlier questions, what
properties of leather do you wish to duplicate? |
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Might be just as easy to make a right-handed cow. |
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My thought is that leather as it stands is
toughened and has certain qualities which are
positive, for instance being hard-wearing, and
others which are not, for instance for many people
being from a dead animal, having chromium
sulphate in it and not being particularly flexible or
elastic. These qualities can be changed if a skin-
like substance can be made from D-amino acids. |
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It may be there's another way of assembling all
that stuff. For instance, the artificial "silk" made
from glutamic acid polymer is biodegradable but
still somewhat silken, or so i hear - never seen it.
I think there might be a way of making this stuff
more simply, i.e. without biological machinery. |
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For all i know, though i realise this is a long shot,
there may be a single amino acid polymer or two
which could simply be matted together to make
the stuff. For instance, cysteine seems like it
might have possibilities to me. |
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//leather as it stands...// |
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So, you want something which is tough and hard-wearing,
more flexible and elastic than leather, and does not come
from dead animals or have heavy metals and other junk in it? |
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I dunno, [19thly]. What you're asking for sounds very much
like a lot of modern synthetic polymer materials. |
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The reason this is here is that some of my friends
want me to investigate the pros and cons of leather
and leather substitutes from an ethical point of
view. Right now, polyurethane looks like a good bet
but i'm also wondering about mammoth hide. I'm
trying to cover as many conceivable options as
possible because i strongly suspect leather is more
ethical than many substitutes. |
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