skillissuer,
@skillissuer@discuss.tchncs.de avatar

update 3: unfortunately i had some time to look back at this, and the longer i thought about that “bacteria but stiffer” thing the more aggressively stupider entire thing becomes. get yourself a mean drink like i did, because it’s long. for your sneering pleasure (and if you want to use it, just rephase relevant bits it’ll be shorter):

here i'm talking out of my ass about psychology, so don't listen to me because i'm not a psychologistZeroth of all, let’s take a few steps back and look at the bigger picture. University allows you to learn, teaches you how to learn, but here one underappreciated thing is that it lets you fail non-catastrophically. Let’s say you know some things, and you arrive at a hypothesis. When you are in some professional environment dedicated to learning, you might be - should be - incentivized to test it: look up some literature, design an experiment, or just ask someone who actually knows. When you are right, you don’t really learn anything new; but when you’re wrong, you learn limitations of your method/approach/reasoning, how to fix them, new things etc but more importantly you learn some humility and nuance, and you learn to answer “it depends”. This of course doesn’t have to happen at university, but I suspect it’s pretty good at it. When you don’t have that, when you never are proven wrong, you might end up sniffing your own farts so hard that you refuse all criticism in the future, never admit that your ideas could be possibly faulty and you become EY. I know that because I’ve come too close for comfort to that path however at the uni some half year in where i had to do actual lab work cured me of it irreversibly when reality proved me wrong. I’ve also seen one case of exactly that on /r/chemistry, in that case there also was a complete lack of self-awareness about their own limitations, not really unlike of EY’s in principle, but he had more time to learn it. I can elaborate in DMs if anyone is so inclined

Everything breaks 1For reasons that might be related to the above all rat’s nanomachines are perfect, never malformed, work flawlessly, fibers are infinite and without defects etc etc. Bitch, in real life everything breaks all the time, and yet reality and real things work. To illustrate this consider single kevlar fiber. When taken alone, single molecular strand of kevlar is not significantly stronger than polyester, polyethylene, or PVC. However we don’t really use kevlar this way, and what makes kevlar kevlar is how it interacts with itself between strands. Every unit makes 4 rather strong hydrogen bonds perpendicular to strand direction, and perpendicular to both there are 4 quadrupole interactions between aromatic units. This all arranges single strands into sheets and sheets are then stacked parallel to each other. Now, let’s try to pull a single strand out of bulk material. When strands are short, it’s the hydrogen bonds and quadrupole interactions that break - strands just slip off and separate. However, above certain length, it’s easier to break single strand than to pull it out. That length turns out to be quite small. Going for a ballpark figure, benzene C-H bond has dissociation energy of some 113 kcal/mol, while (quite similar) beta-sheet hydrogen bonds have some 4-9kcal/mol, depending on who you ask and how you measure. That works out to some 4 to 7 fully hydrogen-bonded diamine-diamide units are already held in place with more force by hydrogen bonds than single covalent bond can withstand, and that’s without considering quadrupole interactions. This has interesting consequence: as long as you can make sure that at least some of the time neighboring strands have these 30 or more hydrogen bonds between them, under tension they don’t slip - failure mode shifts. This means that kevlar tolerates some breaks, a very important property in a world where everything breaks. There’s still benefit to strands longer than that - it allows for increased tensile strength, to a degree - but it’s these weaker hydrogen bonds that make kevlar what it is, an interaction that EY dismisses outright as some superfluous bullshit not worthy of attention. Exactly the same thing applies to peptide beta-sheets and collagen, keratin and such, which have similar hydrogen bonding pattern but this time after 3 strands it wraps over, making 3-strand helix. As it happens, alpha-aminoacid based peptides pack pretty much as many amide bonds per chain length as humanely possible, so these hydrogen-bonds-collevtively-are-stronger-than-strand segments are even shorter than in kevlar. These are actual structural proteins that are part of the reason that cells hold shape. Same goes for cellulose, chitin and to some degree lignin. The above is also the reason why i think that this bond counting metric is pretty useless, and that’s before ionic and vdW interactions swamp the entire picture. You can arrive at something more useful by counting bond energies by type, but this still makes sense only in context, because you might break single covalent bond vs bunch of hydrogen like above, so shape is also important. Even this wouldn’t be massively useful, but that could be better. But i digress

Nanomachines, sonEY makes a big point of how living thingies lack wheels, and his imaginary nanomachines have wheels, which makes them superior (yes i know about ATP synthase, this is not the point). I’m not convinced on how adding wheels on perfectly wheelless bacteria would improve them in any way, especially when what you need is something else. Square-cube law is binding here and in full effect - noncompliance is punished by inefficiency, and energy is something that will be very useful. There are already strings, levers, shuttles, springs, elastic membranes, one-way and two-way pumps and valves, some gated by external signal, and even a tiny conveyor belt at this scale. We don’t need no wheels where we’re going I’m not sure how this entire thing would maintain integrity and remain isolated from external environment. Actual biology uses for this lipid bilayer, which can’t be easily damaged in some ways because it’s literally liquid, what’s more it can absorb some insults, it can conform to surface, it can replace its components at will - all you need to do is to overcome these weak interactions (hydrophobic in this case) and you can pull out some protein, shred it into aminoacids, and make it anew. You can’t do any of this with stiff, crosslinked sheets of graphane (or something) Lipid bilayer has a very important function that even a small break kills catastrophically - it stores energy by way of electrical and chemical gradient across it. When it breaks, you’re proper fucked - fortunately, these weak interactions allow for membrane to reform where it was punctured. This fails badly when membrane is stiff for obvious reasons. Membrane also needs to be thick: we’re talking about some 150mV across some 5nm of membrane of a living bacterial cell, which in already existing biological systems means 30kV/mm, and can withstand much more. What was that supposed benefit? Higher energy/power density? You would need to think really hard about making materials that can withstand this and higher fields. Note: real life example already uses pretty much the best material for the job

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