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).
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
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.
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.
> “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?
>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.
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.
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.
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?
> 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?
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
https://www.nature.com/articles/s41377-020-00367-8
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.
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.
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.
fun fact some left handed amino acids are poisonous to most mammals
> “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?
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
How suggestive is this of life elsewhere in the universe?
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.
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.
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?
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.
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?
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.