On 23-07-2019 04:10, 'Brent Meeker' via Everything List wrote:
On 7/22/2019 3:55 PM, smitra wrote:
This doesn't address the fundamental problems. People like Leslie
Orgel have explained why metabolism first is a non-starter.
And you think Nick Lane hasn't read Orgel?
Orgel's original arguments can be generalized into a no-go argument that
precludes all existing biochemical models for abiogenesis. This has been
pointed out by Paul Davies. However, Davies then argues that this means
that the problem lies with the fundamental laws of physics, but one can
also circumvent the problems raised by sticking to ordinary physics and
getting to the right structures within which the conventional models can
work.
He has argued on the basis of the difficulties of getting to
functional RNA, and more recently people like Paul Davies have pointed
out the fundamental nature of this problem. My suggestion is not some
new model, it simply makes conventional models such as e.g. the
protocell work better by putting these in a micro-environment that
itself has been forged in far from equilibrium conditions. The
micro-environments break the symmetry that can steer the chemistry
that takes place inside more coherently in one or the other direction
compared to whatever chemistry can go on in a macroscopic environment.
Keep in mind that the simplest functional living organism is likely
going to be similar to a microbe, involving hundreds of thousands of
different enzymes that are then all necessary to make each other and
maintain and copy the organism. There thus exists a massive gap from
simple chemistry to the simplest self-reproducing lifeforms. The only
plausible solution is then a scenario where simpler systems that would
not function good enough to be able to reproduce with a multiplication
factor of larger than one, can reproduce with a multiplication factor
larger than 1 in a protected environment.
Which Lane and others postulate to alkaline "white smokers".
This is impossible, because you need to build structures on the
molecular scale without the enzymes that living organisms have
available. Local thermal equilibrium won't allow chemical reactions to
proceed differently a few atoms distance away at one site of a large
molecule compared to another. So, one needs to consider processes in an
environment where local thermal equilibrium will be violated on a
molecular scale. This can happen in a cryogenic environment in space
where UV radiation creates radical and ions and occasional cosmic ray
interaction causes heating allowing nearby ions and radicals to form
bonds. Such processes have been studied with the ail of getting to the
fundamental building blocks of life, but that doesn't really work
because of the random nature of the products.
But under those conditions one will also get extremely large clusters of
organics, and they can serve as the housing within which one can have
the right structures for conventional models to work. Confinement in a
small volume is essential as there will be as small number of structures
inside each such system. This means that the net effect of all the
structures inside any particular system will differ due to statistical
fluctuations. In a larger volume, the average effects of the structures
would average out to some mean effect, also the effect the structures on
the surface have on the chemistry taking place in the entire volume
would be less the larger the volume becomes.
Saibal
Brent
But that environment must then have features that would have to play
the role of the more sophisticated molecular machinery that makes the
more advanced life forms work. Fixed features on the inner surface
area of a micro-environment can then work. The effect such features
have over the entire volume can be non-negligible in a small system.
Saibal
On 07-07-2019 08:32, 'Brent Meeker' via Everything List wrote:
I think Nick Lane's metabolism-first theory, which he discusses in
his
book "The Vital Question", is more plausible. There's good online
talk by Lane https://www.youtube.com/watch?v=PhPrirmk8F4.
Brent
On 7/6/2019 8:32 AM, smitra wrote:
https://arxiv.org/abs/1711.01945
A followup article which focuses more on the mathematical issues is
under construction, the key points are:
1) In interstellar space, simple organic compounds captured in small
ice grains were subject to UV radiation and occasional heating due
to incident cosmic rays (CR). This induced a bond percolation
process that led to large clusters of organic molecules on a time
scale of $\gtrsim 10^6$ years.
2) On a proto-planet, such clusters can merge into loosely bound
superclusters. The deep interior of such superclusters can provide
for chemical micro-environments in which conventional models of
abiogenesis driven by cold-warm cycles can be considered.
3) Rapid fluctuations in the chemical potentials of certain chemical
compounds that can penetrate the supercluster, will be damped down.
Long term gradual and periodic changes then dominate, allowing any
biochemical systems inside the superclusters to more easily evolve
toward exploiting the conditions in their micro-environments,
compared to a similar system in the outside environment.
4) As the supercluster breaks up, the system experiences more of the
shorter term fluctuations that has more of a random character. The
system can then evolve to adapt to these fluctuations, when doing so
right from the start might not have worked.
5) On a small fraction of the superclusters these processes led to
microbes capable of surviving in the outside environment.
6) Microbes were transferred to Earth via a collision of a
microbe-containing proto-planet with the Moon. Fragments containing
microbes resulting from the giant impact rained down on the Earth.
Saibal
On 06-07-2019 10:48, 'Cosmin Visan' via Everything List wrote:
https://www.youtube.com/watch?v=r4sP1E1Jd_Y [1]
--
You received this message because you are subscribed to the Google
Groups "Everything List" group.
To unsubscribe from this group and stop receiving emails from it,
send an email to everything-list+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/a43531f9-d34c-4806-97f0-7665befc7e95%40googlegroups.com
[2].
Links:
------
[1]
https://www.youtube.com/watch?v=r4sP1E1Jd_Y&fbclid=IwAR03cRVkBTOeYnPldcuLzFGCNiWqCR0dE5FENXF9JJtRlk75sbq5Dh2wxcY
[2]
https://groups.google.com/d/msgid/everything-list/a43531f9-d34c-4806-97f0-7665befc7e95%40googlegroups.com?utm_medium=email&utm_source=footer
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to everything-list+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/51363e5757e99cef0f91ea9bb2713ad5%40zonnet.nl.
