[HN Gopher] NASA: Mystery of Life's Handedness Deepens
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NASA: Mystery of Life's Handedness Deepens
Author : bookofjoe
Score : 50 points
Date : 2024-11-22 14:35 UTC (2 days ago)
(HTM) web link (www.nasa.gov)
(TXT) w3m dump (www.nasa.gov)
| robthebrew wrote:
| https://www.nature.com/articles/s41377-020-00367-8
| __MatrixMan__ wrote:
| That's a relevant paper, but this is the one which "deepened"
| the mystery: https://www.nature.com/articles/s41467-024-52362-x
|
| It asserts:
|
| > L-proteins need not emerge from a D-RNA World
|
| So if more than one amino acid chirality could have emerged,
| why did we get the one we got and not several?
|
| From the paper in the parent comment:
|
| > Achiral linearly polarized light interacts with chiral
| objects and their enantiomers differently. An interesting
| example is a light-driven motor. Linearly polarized light can
| rotate a gammadion-shaped gold structure embedded in a silica
| block as a motor.
|
| Imagine you were using some kind of optical tweezers to
| manipulate chiral molecules. I wonder if there's a reason that
| such a device would work better if you had a sample which had
| the same chirality. Suppose so...
|
| If one of your samples made its way to Earth and replicated...
| Well that would be a reason for earth proteins to be biased in
| one direction, despite the laws of physics not prescribing such
| a bias.
| madaxe_again wrote:
| https://en.m.wikipedia.org/wiki/Optical_tweezers
|
| I suppose there's no reason you couldn't use circularly
| polarised light to achieve the effect you're talking about.
| throwawaymaths wrote:
| What is the mystery? Perhaps one handedness was just first by
| chance and won because it self replicated the other handedness
| away by consuming it as food.
| griffzhowl wrote:
| Well, that's the question isn't it? Is it just a frozen
| accident, or is there some nonarbitrary reason for the left-
| handed molecules to be favoured?
| madaxe_again wrote:
| Perhaps aliens eat right handed life, but left handed life is
| poison to them.
|
| Seriously. It would be a pretty good selector, and said
| "alien" need be no more than a snippet of RNA - and it would
| be entirely gone from earth now, eliminated by us sinister
| life forms.
|
| The only evidence would be the ubiquitous absence of
| R-entantiomers in life.
|
| I think I might be lifting from Asimov - _The Left Hand of
| the Electron_.
| andrewflnr wrote:
| While all right-handed amino acids would presumably be fine, do
| we have any idea whether mixed chirality would work? I suspect
| no, since they presumably have different folding behavior but
| might be tricky to distinguish chemically during the protein
| synthesis process, making e.g. different codons for left and
| right-handed amino acids infeasible to implement. I'd love to
| hear from a biologist whether any of that is correct.
| fredgrott wrote:
| fun fact some left handed amino acids are poisonous to most
| mammals
| gilleain wrote:
| So a couple of things i remember from back in the old
| structural bioinformatics days...
|
| Firstly, there are naturally occurring mixed-chirality
| (alternating) peptides. They are usually circular iirc.
|
| Secondly, no you can't really have larger proteins with both
| left and right (ignoring glycine). They would not fold into
| nice helix/sheet strucures and likely just be random coil.
|
| For cells to have mixed populations of all-L and all-R proteins
| would mean doubling up all the machinery for creating them.
|
| One theory that I thought was reasonable for why there's a
| monochiral world is that once the arbitrary choice is made (L
| or R) then that gets 'locked in' by all the machinery around
| that choice. As in, L 'won'.
| westurner wrote:
| From "Amplification of electromagnetic fields by a rotating body"
| https://news.ycombinator.com/item?id=41873531 :
|
| > _ScholarlyArticle: "Amplification of electromagnetic fields by
| a rotating body" (2024)
| https://www.nature.com/articles/s41467-024-49689-w _
|
| >> _Could this be used as an engine of some kind?_
|
| > _What about helical polarization?_
|
| If there is locomotion due to a dynamic between handed molecules
| and, say, helically polarized fields; is such handedness a
| survival selector for life in deep space?
|
| Are chiral molecules more likely to land on earth?
|
| > _" Chiral Colloidal Molecules And Observation of The Propeller
| Effect" https://pmc.ncbi.nlm.nih.gov/articles/PMC3856768/_
|
| > _Sugar molecules are asymmetrical / handed, per 3blue1brown and
| Steve Mould. /?
| https://www.google.com/search?q=Sugar+molecules+are+asymmetr..._
| _https://www.google.com/search?q=Sugar+molecules+are+asymmetr..._
|
| > _Is there a way to get to get the molecular propeller effect
| and thereby molecular locomotion, with molecules that contain
| sugar and a rotating field or a rotating molecule within a
| field?_
| westurner wrote:
| Though, a new and plausible terrestrial origin of life
| hypothesis:
|
| Methane + Gamma radiation => Guanine && Earth thunderstorms =>
| Gamma Radiation
| https://news.ycombinator.com/item?id=42131762#42157208 :
|
| > _A terrestrial life origin hypothesis: gamma radiation
| mutated methane (CH4) into Glycine (the G in ACGT) and then DNA
| and RNA._
| nativeit wrote:
| > "We are analyzing OSIRIS-REx samples for the chirality
| (handedness) of individual amino acids, and in the future,
| samples from Mars will also be tested in laboratories for
| evidence of life including ribozymes and proteins," said Dworkin.
|
| I clicked the hyperlink for OSIRIS-REx samples, and it didn't
| contain any information about what kinds of materials were found,
| but this statement suggests amino acids were collected from
| OSIRIS-REx--did I miss this news? Were there proteins found on an
| asteroid?
| nativeit wrote:
| Indeed I did miss that, what an incredible find, I can't
| believe this never broke through into my routine news feeds!
|
| https://www.hou.usra.edu/meetings/lpsc2024/pdf/1219.pdf
| jebarker wrote:
| How suggestive is this of life elsewhere in the universe?
| jcims wrote:
| Only tangentially related, but because they are so amazing here
| are a few videos that illustrate the process of transcription
| (creating mRNA from DNA) and translation (creating a protein from
| mRNA).
|
| https://www.youtube.com/watch?v=SMtWvDbfHLo
|
| https://www.youtube.com/watch?v=TfYf_rPWUdY
|
| The common complaint with these videos is that everything is more
| complex. One thing that isn't evident is that these specific
| videos (built mostly by Drew Barry) actually model a lot of other
| molecules to create a more realistic physical environment with
| brownian motion and whatnot. Then the irrelevant molecules are
| simply made transparent in the rendering.
|
| Obviously it's still much much more complex (eg the constant
| stream of ATP used to drive many of these operations is not
| illustrated).
|
| There are these and many more great illustrations/explanations at
| WEHImovies on youtube
|
| https://www.youtube.com/@WEHImovies
| Mistletoe wrote:
| https://www.smithsonianmag.com/space/must-all-molecules-life...
|
| More explanation here.
|
| >Oftentimes both the left- and right-handed versions of, for
| example, an amino acid, were found in equal amounts--exactly what
| might be expected. But in many cases, one or more organic
| molecule was found with an excess of one hand, sometimes a very
| large excess. In each of those cases, and in every meteorite
| studied so far by other researchers in the field, the molecule in
| excess was the left-handed amino acid that is found exclusively
| in life on Earth.
| polishdude20 wrote:
| Could these asteroids be from when the moon was created?
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