origin of biological chirality?

[Ernest Major]

A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

[Bob Casanova]

On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

[RonO]

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms. My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started. The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides. The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before. Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution. I really do not understand why
anyone is worried about why life on earth uses D sugars and L amino
acids. It would have been set, probably, by the enzymes of the first
self replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the same
materials.

I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins using
ribosomes, mRNA and tRNAs) because both D and L amino acids transition
between the 2 and 3 position of the ribose (at the end of the tRNA)
several times a second, but L forms are found more often at the 3
position that is used in the translation system. It is a reason to use
L amino acids to make proteins using our current translation system, but
L amino acids would have been selected long before by their use in
making nucleotides and other essential biochemicals for the lifeform
before the translation system existed.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/

Ron Okimoto

[Bob Casanova]

On Sun, 18 Aug 2024 13:37:19 -0500, the following appeared

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms. My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started. The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides. The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before. Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution. I really do not understand why
anyone is worried about why life on earth uses D sugars and L amino
acids. It would have been set, probably, by the enzymes of the first
self replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the same
materials.
I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins using
ribosomes, mRNA and tRNAs) because both D and L amino acids transition
between the 2 and 3 position of the ribose (at the end of the tRNA)
several times a second, but L forms are found more often at the 3
position that is used in the translation system. It is a reason to use
L amino acids to make proteins using our current translation system, but
L amino acids would have been selected long before by their use in
making nucleotides and other essential biochemicals for the lifeform
before the translation system existed.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/

OK; thanks.

So if I understand what you wrote, while there are
similarities between chirality selection and m/am in the
sense that both involve equally-likely (chemically) forms,
the former involves, at least somewhat, preferential
selection for incorporation into living things while the
latter is (AFAIK) a matter of pure chance. Sound right?

[RonO]

Post by Bob Casanova
On Sun, 18 Aug 2024 13:37:19 -0500, the following appeared

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms. My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started. The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides. The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before. Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution. I really do not understand why
anyone is worried about why life on earth uses D sugars and L amino
acids. It would have been set, probably, by the enzymes of the first
self replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the same
materials.
I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins using
ribosomes, mRNA and tRNAs) because both D and L amino acids transition
between the 2 and 3 position of the ribose (at the end of the tRNA)
several times a second, but L forms are found more often at the 3
position that is used in the translation system. It is a reason to use
L amino acids to make proteins using our current translation system, but
L amino acids would have been selected long before by their use in
making nucleotides and other essential biochemicals for the lifeform
before the translation system existed.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/

OK; thanks.
So if I understand what you wrote, while there are
similarities between chirality selection and m/am in the
sense that both involve equally-likely (chemically) forms,
the former involves, at least somewhat, preferential
selection for incorporation into living things while the
latter is (AFAIK) a matter of pure chance. Sound right?

The forms do not have to be equally likely in solution. As I noted D
glucose is found at over 60% at equalibrium with the L form. If you
have ever worked with the stick models the carbon backbone has to twist
into the mirror image in order to change from one form to the other. It
makes them structurally different in 3 dimensions. For enzymes that use
these molecules usually only one mirror image fits into an active site.
A molecule has to get into position so that one of it's bonds can be
broken or two molecules have to be brought into close enough proximity
for their reaction to be catalyzed by the enzyme.

Whether the D or L form was utilized would have been set by the first
enzymes. The first self replicators would have likely had some type of
catalytic site or sites within their structures. These catalytic sites
would have preferred one form over the other.

Both D and L forms existed in solution, but only one would work in any
enzyme that evolved to deal with those carbon molecules.

Ron Okimoto

[Pro Plyd]

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images. D
sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.  The
chirality of life was set by the first enzymatic reactions used by life
to get started.  The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides.  The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before.  Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it

https://en.wikipedia.org/wiki/Spock_Must_Die!

Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

[Bob Casanova]

On Sun, 18 Aug 2024 21:11:53 -0600, the following appeared
in talk.origins, posted by Pro Plyd

Post by Pro Plyd

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images. D
sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.  The
chirality of life was set by the first enzymatic reactions used by life
to get started.  The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides.  The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before.  Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it
https://en.wikipedia.org/wiki/Spock_Must_Die!
Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

Check out the Roger Zelazny novel, "Doorways in the Sand".

[RonO]

Post by Bob Casanova
On Sun, 18 Aug 2024 21:11:53 -0600, the following appeared
in talk.origins, posted by Pro Plyd

Post by Pro Plyd

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images. D
sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.  The
chirality of life was set by the first enzymatic reactions used by life
to get started.  The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides.  The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before.  Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would get
a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it
https://en.wikipedia.org/wiki/Spock_Must_Die!
Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

Check out the Roger Zelazny novel, "Doorways in the Sand".

I took a science fiction English class at Berkeley and one of the reads
was Zelazny's "A Rose for Ecclesiastes". One issue with the story was
the unbelievable interbreeding with the Martians, but in my essay on the
story I proposed that because of the Biblical reference that Zelazny
meant it as evidence for a common creator of both Martians and Humans.

Ron Okimoto

[Pro Plyd]

Post by Bob Casanova
On Sun, 18 Aug 2024 21:11:53 -0600, the following appeared
in talk.origins, posted by Pro Plyd

Post by Pro Plyd

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

stuff for 1970. Moral of the story is that the
chirality preference is universal!

Check out the Roger Zelazny novel, "Doorways in the Sand".

Pretty sure I've read that once upon a time
but don't recall much of it. Had to google it.
Will have to put this on my list of things to
revisit.

[Stewart Robert Hinsley]

Post by Pro Plyd

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.
The chirality of life was set by the first enzymatic reactions used by
life to get started.  The use of L amino acids would have been set by
the first functional proteases that could produce peptide bonds or for
the RNA world scenario it would have been L amino acids that were
probably used to make the first nucleotides.  The active sites of the
first replicated enzymes would have set the chirality, and that
chirality would have been maintained due to subsequent enzymes would
have to be compatible for the ones that came before.  Only one form
fits into the active site of an enzyme that uses that amino acid or
carbohydrate. Enzymes have evolved to convert one form into the other
because they spontaneously change from D to L and if left to
themselves you would get a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it
https://en.wikipedia.org/wiki/Spock_Must_Die!
Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

That is probably based on Arthur C. Clarke's 1950 short story "Technical
Error" (originally published as "The Reversed Man"). (There is also,
judging by descriptions, a more tongue in cheek 1987 story by Isaac
Asimov - "Left to Right".)

https://en.wikipedia.org/wiki/Technical_Error

[Athel Cornish-Bowden]

Post by Stewart Robert Hinsley

Post by Pro Plyd

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started.  The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides.  The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before.  Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would
get a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it
https://en.wikipedia.org/wiki/Spock_Must_Die!
Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

That is probably based on Arthur C. Clarke's 1950 short story
"Technical Error" (originally published as "The Reversed Man"). (There
is also, judging by descriptions, a more tongue in cheek 1987 story by
Isaac Asimov - "Left to Right".)

Remember that Asimov was a biochemist (not a very significant one, but
that's another matter), whereas these other authors were not.

Post by Stewart Robert Hinsley
https://en.wikipedia.org/wiki/Technical_Error

[RonO]

Post by Pro Plyd

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.
The chirality of life was set by the first enzymatic reactions used by
life to get started.  The use of L amino acids would have been set by
the first functional proteases that could produce peptide bonds or for
the RNA world scenario it would have been L amino acids that were
probably used to make the first nucleotides.  The active sites of the
first replicated enzymes would have set the chirality, and that
chirality would have been maintained due to subsequent enzymes would
have to be compatible for the ones that came before.  Only one form
fits into the active site of an enzyme that uses that amino acid or
carbohydrate. Enzymes have evolved to convert one form into the other
because they spontaneously change from D to L and if left to
themselves you would get a mix at a certain ratio in solution.

Quite some time ago I came across (borrowed?) an old
scifi Star Trek novel called "Spock Must Die". There's
even a wiki page for it
https://en.wikipedia.org/wiki/Spock_Must_Die!
Anyways, that bad ol transporter makes a second
Spock. This second Spock was the chiral opposite
of the original Spock and was basically starving
because the food had the wrong chirality. Cool
stuff for 1970. Moral of the story is that the
chirality preference is universal!

Star Trek Next Gen had an episode that explained why humans and vulcans
and Klingons and Humans could produce hybrids. Picard went on a
scavenger hunt across the galaxy to pick up DNA clues, and put together
a holograph that was of the Progenitors that claimed to have seeded life
across the galaxy so that there would be more than one sentient species
in the galaxy. They had the same chirality and DNA because of the
Progenitors.

Ron Okimoto

[Athel Cornish-Bowden]

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms. My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started. The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides. The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before. Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would
get a mix at a certain ratio in solution. I really do not understand
why anyone is worried about why life on earth uses D sugars and L amino
acids.

Me neither. It had to be one or the other, and with appropriate enzymes
D aminoacids would have been just as good, but having made the choice
life had to stick with it.

An interesting case is that of lactate. Both D-lactate and L-lactate
are important metabolites, and the lactate dehydrogenases that act on
them are quite different from one another.

Post by RonO
It would have been set, probably, by the enzymes of the first self
replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the same
materials.
I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins using
ribosomes, mRNA and tRNAs) because both D and L amino acids transition
between the 2 and 3 position of the ribose (at the end of the tRNA)
several times a second, but L forms are found more often at the 3
position that is used in the translation system. It is a reason to use
L amino acids to make proteins using our current translation system,
but L amino acids would have been selected long before by their use in
making nucleotides and other essential biochemicals for the lifeform
before the translation system existed.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/
Ron Okimoto

[RonO]

Post by Athel Cornish-Bowden

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter.
The chirality of life was set by the first enzymatic reactions used by
life to get started.  The use of L amino acids would have been set by
the first functional proteases that could produce peptide bonds or for
the RNA world scenario it would have been L amino acids that were
probably used to make the first nucleotides.  The active sites of the
first replicated enzymes would have set the chirality, and that
chirality would have been maintained due to subsequent enzymes would
have to be compatible for the ones that came before.  Only one form
fits into the active site of an enzyme that uses that amino acid or
carbohydrate. Enzymes have evolved to convert one form into the other
because they spontaneously change from D to L and if left to
themselves you would get a mix at a certain ratio in solution.  I
really do not understand why anyone is worried about why life on earth
uses D sugars and L amino acids.

Me neither. It had to be one or the other, and with appropriate enzymes
D aminoacids would have been just as good, but having made the choice
life had to stick with it.
An interesting case is that of lactate. Both D-lactate and L-lactate are
important metabolites, and the lactate dehydrogenases that act on them
are quite different from one another.

As I indicated these carbon molecules transition between forms in
solution. For some important amino acids cells have enzymes that
convert D amino acids to the L form. For lactate it probably became
important to deal with the terminal product of glycolysis, so instead of
evolving a system to keep changing one to the other, enzymes evolved to
deal with both D and L forms so that the amount of lactate could be
regulated more efficiently.

Ron Okimoto

Post by Athel Cornish-Bowden

Post by RonO
  It would have been set, probably, by the enzymes of the first self
replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the
same materials.
I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins
using ribosomes, mRNA and tRNAs) because both D and L amino acids
transition between the 2 and 3 position of the ribose (at the end of
the tRNA) several times a second, but L forms are found more often at
the 3 position that is used in the translation system.  It is a reason
to use L amino acids to make proteins using our current translation
system, but L amino acids would have been selected long before by
their use in making nucleotides and other essential biochemicals for
the lifeform before the translation system existed.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/
Ron Okimoto

[Athel Cornish-Bowden]

Post by RonO

Post by Athel Cornish-Bowden

Post by RonO

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

For chirality there is an equilibrium ratio between the mirror images.
D sugars have been known to exist in solution at higher concentrations
that L forms.  My guess is that L forms of amino acids are likely to
exist at higher concentrations in solution, but it doesn't matter. The
chirality of life was set by the first enzymatic reactions used by life
to get started.  The use of L amino acids would have been set by the
first functional proteases that could produce peptide bonds or for the
RNA world scenario it would have been L amino acids that were probably
used to make the first nucleotides.  The active sites of the first
replicated enzymes would have set the chirality, and that chirality
would have been maintained due to subsequent enzymes would have to be
compatible for the ones that came before.  Only one form fits into the
active site of an enzyme that uses that amino acid or carbohydrate.
Enzymes have evolved to convert one form into the other because they
spontaneously change from D to L and if left to themselves you would
get a mix at a certain ratio in solution.  I really do not understand
why anyone is worried about why life on earth uses D sugars and L amino
acids.

Me neither. It had to be one or the other, and with appropriate enzymes
D aminoacids would have been just as good, but having made the choice
life had to stick with it.
An interesting case is that of lactate. Both D-lactate and L-lactate
are important metabolites, and the lactate dehydrogenases that act on
them are quite different from one another.

As I indicated these carbon molecules transition between forms in
solution. For some important amino acids cells have enzymes that
convert D amino acids to the L form. For lactate it probably became
important to deal with the terminal product of glycolysis, so instead
of evolving a system to keep changing one to the other, enzymes evolved
to deal with both D and L forms so that the amount of lactate could be
regulated more efficiently.

Yes, but there aren't many examples of reactions that convert achiral
substrates into chiral products (or vice versa). Come to that, apart
from pyruvate there aren't many important achiral metabolites.

Post by RonO

Post by Athel Cornish-Bowden
  It would have been set, probably, by the enzymes of the first self
replicators, and would have likely been maintained by selection as
everything would have worked better if new functions could use the same
materials.

Post by RonO
I found this paper that L amino acids would have been more efficiently
incorporated into our current translation system (making proteins using
ribosomes, mRNA and tRNAs) because both D and L amino acids transition
between the 2 and 3 position of the ribose (at the end of the tRNA)
several times a second, but L forms are found more often at the 3
position that is used in the translation system.  It is a reason to use
L amino acids to make proteins using our current translation system,
but L amino acids would have been selected long before by their use in
making nucleotides and other essential biochemicals for the lifeform
before the translation system existed.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC281674/
Ron Okimoto

[J. J. Lodder]

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.

Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Jan

[Bob Casanova]

On Thu, 22 Aug 2024 09:16:04 +0200, the following appeared

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

OK, I get that. I was only commenting on the prevalence of
one form when neither seemed to be inherently preferred. Ron
corrected me on that; that there apparently *is* a preferred
chirality, at least as to biology.

I seem to remember reading, decades ago, that at least some
of the then-current thinking on the matter/antimatter
imbalance that there was once only a small imbalance, but
that mutual annihilation removed almost all of both, leaving
the current deficit of antimatter. Is that still the case?

[Pro Plyd]

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...

https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book
July 28, 2024

Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

[Ernest Major]

Post by Pro Plyd

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...
https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book
July 28, 2024
Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

Charge conservation is a consequence of "the global gauge invariance of
the electromagnetic field". From the existence of beta decay it can be
deduced that the charges on the proton and positron are the same (unless
you're willing to postulate that neutrinos are charged). From the
existence of electron-positron annihilation it can be deduced that the
charges on the electron and positron are equal in magnitude (unless
you're willing to postulate that photons are charged). From this we can
conclude that the charges on protons and electrons balance each other out.

So we are left to rephrase the question as "why are there equal numbers
of protons and electrons?" (Other charged particles decay to protons and
electrons (and photons and neutrinos) reasonably quickly.

[Bob Casanova]

On Sat, 24 Aug 2024 10:34:20 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major

Post by Pro Plyd

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...
https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book
July 28, 2024
Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

Charge conservation is a consequence of "the global gauge invariance of
the electromagnetic field". From the existence of beta decay it can be
deduced that the charges on the proton and positron are the same (unless
you're willing to postulate that neutrinos are charged). From the
existence of electron-positron annihilation it can be deduced that the
charges on the electron and positron are equal in magnitude (unless
you're willing to postulate that photons are charged). From this we can
conclude that the charges on protons and electrons balance each other out.
So we are left to rephrase the question as "why are there equal numbers
of protons and electrons?" (Other charged particles decay to protons and
electrons (and photons and neutrinos) reasonably quickly.

This sounds to me like a close relative of the Anthropic
Principle, in that a universe in which charge, rather than
gravity, dominates would most likely be one in which life
couldn't exist. IOW, "I am, therefore charges balance."

[Ernest Major]

Post by Bob Casanova
On Sat, 24 Aug 2024 10:34:20 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major

Post by Pro Plyd

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...
https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book
July 28, 2024
Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

Charge conservation is a consequence of "the global gauge invariance of
the electromagnetic field". From the existence of beta decay it can be
deduced that the charges on the proton and positron are the same (unless
you're willing to postulate that neutrinos are charged). From the
existence of electron-positron annihilation it can be deduced that the
charges on the electron and positron are equal in magnitude (unless
you're willing to postulate that photons are charged). From this we can
conclude that the charges on protons and electrons balance each other out.
So we are left to rephrase the question as "why are there equal numbers
of protons and electrons?" (Other charged particles decay to protons and
electrons (and photons and neutrinos) reasonably quickly.

This sounds to me like a close relative of the Anthropic
Principle, in that a universe in which charge, rather than
gravity, dominates would most likely be one in which life
couldn't exist. IOW, "I am, therefore charges balance."

In principle one could apply the Weak Anthropic Principle to place an
upper bound on any charge imbalance. (This is not necessarily a tighter
bound that can be obtained by more direct observations.)

[Bob Casanova]

On Sat, 24 Aug 2024 19:23:00 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major

Post by Bob Casanova
On Sat, 24 Aug 2024 10:34:20 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major

Post by Pro Plyd

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...
https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book
July 28, 2024
Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

Charge conservation is a consequence of "the global gauge invariance of
the electromagnetic field". From the existence of beta decay it can be
deduced that the charges on the proton and positron are the same (unless
you're willing to postulate that neutrinos are charged). From the
existence of electron-positron annihilation it can be deduced that the
charges on the electron and positron are equal in magnitude (unless
you're willing to postulate that photons are charged). From this we can
conclude that the charges on protons and electrons balance each other out.
So we are left to rephrase the question as "why are there equal numbers
of protons and electrons?" (Other charged particles decay to protons and
electrons (and photons and neutrinos) reasonably quickly.

This sounds to me like a close relative of the Anthropic
Principle, in that a universe in which charge, rather than
gravity, dominates would most likely be one in which life
couldn't exist. IOW, "I am, therefore charges balance."

In principle one could apply the Weak Anthropic Principle to place an
upper bound on any charge imbalance. (This is not necessarily a tighter
bound that can be obtained by more direct observations.)

Point taken. Thanks.

[J. J. Lodder]

Post by Pro Plyd

Post by J. J. Lodder

Post by Bob Casanova
On Sun, 18 Aug 2024 00:08:49 +0100, the following appeared
in talk.origins, posted by Ernest Major

Post by Ernest Major
A study has found that lipid membranes can be selectively permeable to
one or the other sugar or amino acid enantiomer. The study used membrane
models inspired by the membranes of modern organisms, so is not directly
relevant to abiogenesis. However it still raises the possibility that
membrane selectivity was the source of chirality in biological
molecules. One possible issue is does this effect require chiral
membrane lipids; if so it only move the question of the origin of
chirality from sugars and amino acids to lipids.

ISTM that this is similar to the "matter/antimatter"
imbalance; neither is inherently more "natural" than the
other, but one became more prevalent. And IIRC, the m/am
imbalance is now assumed to be a matter of chance in the
original ratio. I could; of course, be mistaken in that;
it's been years since I followed it even casually.

Post by Ernest Major
https://www.biorxiv.org/content/10.1101/2024.04.23.590732v2.full.pdf

It isn't. The left-handed molecules can be converted into right-handed
ones, and vica versa, by taking them apart and reassembling them.
For matter/antimatter there is no such possibility.
Disassembling doesn't help,
because you cannot turn antiquarks into quarks.
Biological chirality is a triviality,
the matter/antimatter imbalance is a deep problem.
Where has all that antimatter gone?

Well, sorta agree with the analogy if one only
is considering the ratio. But also agree with the
observation about matter/anti-matter not being
able to be turned into their opposites. Just
happened to come across the following, another
mystery of sorts...
https://www.livescience.com/physics-mathematics/particle-physics/a-remarkable-

conspiracy-why-is-matter-neutral-physicist-frank-close-explores-the-mystery-in-a-new-book

Post by Pro Plyd
July 28, 2024
Since the discovery of the proton and the
electron in the 20th century, a mystery
persists at the core of the atom: Despite
belonging to completely different particle
families and being radically different in
size, the charges of these two particles
completely balance each other out — enabling
a universe where gravity dominates. But why?
...

Not really, because protons can decay into positron + neutron,
under suitable nuclear circumstances. (and perhaps by itself)

So the proton charge must equal the positron charge,
hence the electron charge.
If there would be a charge imbalance it could be reduced
to an in-family imbalance, either positron not equal electron,
or quarks not precisely 1/3 and 2/3,

Jan
(or worse, charge not strictly conserved)