Question For Tyler and/or others

TomHendricks474 <[email hidden]> wrote or quoted:

Quoted message said:

I read this quote from a textbook with 2000 c.

"Graham Cairnes-Smith (suggests that) RNA nucleotides and
amino acids became associated in such a way that
polypeptides were ordered by and helped synthesize
RNA...This hypothesis suggests that both polypeptides and
RNA arose at the same time."

I tend to agree that they did. I did not know that Cairnes
- Smith did too. Does anyone know exactly how he thought
the two might arise at the same time and under what
conditions?

I don't.

My brief search revealed that he rarely mentions
polypeptides - and the places where he does so don't seem to
have much to say about this issue.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

<< I don't.

My brief search revealed that he rarely mentions
polypeptides - and the places where he does so don't seem to
have much to say about this issue. -- >>

I don't either. I thought that since this book's copyright
was so recent, there might have been info I was not aware of

[email hidden] (TomHendricks474) wrote in message news:<[email hidden]>...

Quoted message said:

I read this quote from a textbook with 2000 c.

"Graham Cairnes-Smith (suggests that) RNA nucleotides and
amino acids became associated in such a way that
polypeptides were ordered by and helped synthesize
RNA...This hypothesis suggests that both polypeptides and
RNA arose at the same time."

I tend to agree that they did. I did not know that Cairnes
- Smith did too. Does anyone know exactly how he thought
the two might arise at the same time and under what
conditions?

Tom, Since you found a quote from Tim's hero that kind-of
supports your views, I thought you might be interested in a
couple of papers from two of my FeS heros that also kind-of
support you. Jim

An All-Purine Precursor of Nucleic Acids Gunter
Wachtershauser Proceedings of the National Academy of
Sciences of the United States of America, Vol. 85, No. 4.
(Feb. 15, 1988), pp. 1134-1135. Stable URL: links.jstor.orgsiciOpen ↗
8424%2819880215%2985%3A4%3C1134%3AAAPONA%3E2.0.CO%3B2-H
Abstract The theory is proposed that the pyrimidines in
extant nucleic acids are postenzymatic substitutes for their
isoelectronic and isogeometric position 3-bonded purine
analogs xanthine and isoguanine, which were sibling products
in a preenzymatic de novo purine pathway.

Selection by Differential Molecular Survival: A Possible
Mechanism of Early Chemical Evolution Christian De Duve
Proceedings of the National Academy of Sciences of the
United States of America, Vol. 84, No. 23. (Dec. 1, 1987),
pp. 8253-8256. Stable URL: links.jstor.orgsiciOpen ↗
8424%2819871201%2984%3A23%3C8253%3ASBDMSA%3E2.0.CO%3B2-P
Abstract A model is proposed to account for selective
chemical evolution, progressing from a relatively simple
initial set of abiotic synthetic phenomena up to the
elaborately sophisticated processes that are almost
certainly required to produce the complex molecules, such as
replicatable RNA-like oligonucleotides, needed for a
Darwinian form of selection to start operating. The model
makes the following assumptions: (i) that a small number of
micromolecular substances were present at high
concentration; (ii) that a random assembly mechanism
combined these molecules into a variety of multimeric
compounds comprising a wide repertoire of rudimentary
catalytic activities; and (iii) that a lytic system capable
of breaking down the assembled products existed. The model
assumes further that catalysts supplied with substrates were
significantly protected against breakdown. It is shown that,
by granting these assumptions, an increasingly complex
network of metabolic pathways would progressively be
established. At the same time, the catalysts concerned would
accumulate selectively to become choice substrates for
elongation and other modifications that could enhance their
efficiency, as well as their survival. Chemical evolution
would thus proceed by a dual process of metabolic extension
and catalytic innovation. Such a process should be largely
deterministic and predictable from initial conditions.

Thanks for both of these and their abstracts (url access
was denied)

<< An All-Purine Precursor of Nucleic Acids Gunter
Wachtershauser >>

Fascinating - I continue to think there may well have been a
'purine' world early on. RNA could well have formed without
base pairing - at least at first. And/or with non WC base
pairing. This seems to reinforce that idea somewhat.

<< Selection by Differential Molecular Survival: A Possible
Mechanism of Early Chemical Evolution Christian De Duve
(snipped) Abstract A model is proposed to account for
selective chemical evolution, progressing from a relatively
simple initial set of abiotic synthetic phenomena up to the
elaborately sophisticated processes that are almost
certainly required to produce the complex molecules, such as
replicatable RNA-like oligonucleotides, needed for a
Darwinian form of selection to start operating. The model
makes the following assumptions: (i) that a small number of
micromolecular substances were present at high
concentration;

TH Agreed.

(ii) that a random assembly mechanism combined these
molecules into a variety of multimeric compounds
comprising a wide repertoire of rudimentary catalytic
activities; and

TH Disagree. How can you have such molecular randomness in a
very nonrandom environment? Life does not pop up and then
face selection as most current scenarios contend. It was
that which always was chemically best suited to surviving
that environment. There was no random assembly mechanism -
it was temperature, and any random assembly aspects, would
then be chemically and prebiotically 'selected' in that
temperature cycle. The assembly mechanism was the heat cycle
- that set up a chemically symnbiotic temperature zones
where certain reactions worked, others did not. The most
noticable temp zone is the range of liquid water.

(iii) that a lytic system capable of breaking down the
assembled products existed. The model assumes further
that catalysts supplied with substrates were
significantly protected against breakdown.

TH The heat cycle would bothuild up and break down.

It is shown that, by granting these assumptions, an
increasingly c Zomplex network of metabolic pathways would
progressively be established.

TH Only if there was a nonrandom heat cycle pushing it.
Randomness by itself could not lead to life.

At the same time, the catalysts concerned would accumulate
selectively to become choice substrates for elongation and
other modifications that could enhance their efficiency, as
well as their survival. Chemical evolution would thus
proceed by a dual process of metabolic extension

TH This is a leap of millions of years to say that anything
would want, need, or profit from metabolic extension. If so
why didn't water, salt, or gold latch on and begin to use
energy to replicate? There must be a reason for metabolism.
It grew as one of the novel ways to survive a heat cycle -
specifically the high end of,

and catalytic innovation. Such a process should be largely
deterministic and predictable from initial conditions.

Quoted message said:

Quoted message said:

Comment? Tom