SoylentNews is people
SoylentNews
Amino acids are just what their name implies: they have an acidic group on one side of the molecule and a nitrogen-containing amino group on the other. It's possible to link these two groups together in a reaction that releases a water molecule. Once linked, they're stable, but the reaction that links them isn't energetically favorable. So, people pondering the origin of life have wondered whether there was a pathway in which the bond could could form spontaneously.
One possible method for getting it to form would be for a solution of amino acids to dry out. As the solution becomes ever more concentrated, a reaction that produces a water molecule could become favorable even if it's expensive in purely energetic terms. But so far, the reaction conditions to get this to work have been rather extreme.
The researchers involved in the new work figured that the amino acids might be alone in these puddles as they dried out. A related chemical, called lactic acid, is thought to have been present on the early Earth. And that can undergo a polymerization reaction that releases water, very similar to that of the amino acids. The difference is that this reaction is more energetically favorable. Simply putting lactic acid on its own through four wet/dry cycles allowed chains of four or more units to form, all connected by what's called an ester bond.
The impressive part is what happens when you mix lactic acid with an amino acid: you start forming mixed chains of molecules. While the amino acid won't normally participate in these reactions, they can break the ester bond, essentially replacing one of the lactic acids. So, a few wet/dry cycles produces a chain that's a mix of lactic acids and amino acids.
The skirt of a geyser would be one place with frequent wet/dry cycles and plenty energy to boot. Did life begin next to Old Faithful?
(Score: 2) by VLM on Tuesday July 21 2015, @04:32PM
Simply putting lactic acid on its own through four wet/dry cycles allowed chains of four or more units to form, all connected by what's called an ester bond.
I have a spool of polylactic acid filament on my 3d printer like many people do. Its a nice plastic. It costs almost nothing more than ABS (like 10% more) and unlike ABS does not stink.
Anyway I'm well aware that "something funny happened in the lab" is a long way from shipping to end users, but its none the less interesting that maybe someday 3d printers will be hooked up to tanks of lactic acid instead of having spools of filament. Squirt lactic acid layer and let it polymerize into PLA in position. Or, what if you could make filament at home using some kind of gadget.
Going the opposite direction I know people are really unhappy when their filament adsorbs water (fingerprints, whatever) and spits it out in the nozzle as steam making ugly prints. I wonder if protein from skin flakes or whatever can overly cross link PLA into clogging nozzles which is an entirely different problem, I'm just proposing its an alternative contamination failure mode. Although stereotypically clogged nozzle is caused by people running the heater up to 250C and turning the PLA into tar, or having mechanical issues. I've noticed 3d printing seems to attract people with no mechanical or electrical or computational skills almost out of nowhere and they then have all manner of problems which they discuss on forums.
Another interesting topic is adhesion. I print on medically clean sterile (cleaned with medical ethanol cleaning pads, like $5 for 500 disposable pads) heated kapton and it works perfectly, lasts forever, and detaches all by itself when it cools. I run 70C bed which some claim is too hot. Anyway the heated bed draws more electrical power than the whole rest of the printer so maybe some kind of magic polymerization spray based on protein could help PLA stick to the bed. Kapton is pretty cool, I used it a lot for electronics and never really thought I'd ever squirt plastic on to it, but here we are.
Again all of the above is with knowledge that "something funny happened in the lab" is a long way from shipping working product. Still polymerizing your own lactic acid is interesting to think about.
(Score: 1, Funny) by Anonymous Coward on Tuesday July 21 2015, @04:36PM
wtf?
(Score: 0) by Anonymous Coward on Tuesday July 21 2015, @07:35PM
Forget it, he's rolling.
(Score: 0) by Anonymous Coward on Tuesday July 21 2015, @07:36PM
Q: "What are you thinking about honey?"
A: "Polymerizing my own lactic acid"
I don't really know the procedure you are describing, but is it that you want a way to reversibly adhere PLA to kapton at lower (less than 70C) temperatures?
(Score: 2) by VLM on Wednesday July 22 2015, @11:29AM
Don't think so. The liquid 200C PLA solidifies when it hits the 70C kapton and it can't be removed without destroying the kapton or the PLA, or at least peeling the kapton off the printer bed, while the bed remains above 50C or so. But once the bed cools to room temp the PLA practically falls off by itself. The trick is something to do with the PLA being flexible enough at 70C that you'd have to shear the entire bond at once, but at room temp its non-flexible enough that it kind of peels off due to thermal expansion.
If you're sloppy you can buy and install a new piece of kapton sheet every print, or every week or whatever. I've been using the same sheet for months, kilos of printed plastic. Gotta keep it clean with medical alcohol wipes, dust and finger oil ruin the bond.
I bet if you heated the bed up to 100C, after you put the fire out (LOL, a lot of the "electronic stuff" probably isn't rated for that) you could probably mush PLA into kapton and expect it to stick, so you could reversibly stick it and remove it like a ridiculous simulation of velcro. But that exceeds your "under 70C" criteria.
(Score: 2) by c0lo on Tuesday July 21 2015, @10:52PM
Wikipedia entry on PLA [wikipedia.org]:
Seems that polymerizing your own lactic acid will required 200°C under mild vaccum to get rid of the water generated in the reaction.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford