TH
> I tend to think that RNA and peptides were brought
> together for no other reason than 1. they better
> survived the heat cycle together than apart.

I wonder whether you mean this:  that RNA with
shapes that tend to stick to peptides became more
prevalent, (and peptides with shapes that tend to
stick to RNA).

TH
It may not just be shape - but I think there was
something that made them more stable together
than apart. There's a real problem in the origin
- why would RNA  need protein. So why did
the two connect?

> 2. they were attached by an intermediary - ATP
> which helped  energize both. Thus wherever the
> ATP was - anything around it would be helped.


I think of ATP as rather like dynamite:  possibly
useful if there is a complex control procedure
for using it, but merely dangerous otherwise.
I suppose ATP usage came in at a later stage of
evolution than protein manipulation.
Before that, I imagine life got its energy from the
implicit energy in free RNA bases and free amino
acids (from lightning or whatever).
Also, I imagine ATP is rather unstable and wouldn't
be sitting around in large quantities waiting for
life to use it.

TH
Perhaps.  I was trying to think of something
that would support both - and ATP chemical energy
seemed like the best choice, not for energy, but as joining the two to make the
product more stable. 
tRNA ends in A base
on the stem, and energy is needed to join it to
amino acids. How convenient if the ATP molecule
was the glue that connected both.


I'm assuming RNA pops into existence the way
amino acids do -- I mean, is the
result of nonliving chemical interactions.
I don't know whether that's been
observed, but it seems more plausible
to me at the moment than other possible origins of life.

TH
bases are much more difficult to form in prebiotic
experiments than amino acids.
IIRC Sugars aren't stable and where does
the phosphorus come from.

> 3. later I think there was a general coupling
> of the more prevalent purine bases with the more
> prevalent hydrophilic amino acids, and the
> less prevalent pyrimidines (due to UV dimers)
> with the less prevalent hydrophobic amino acids.

Interesting idea.

> And this set up the genetic code.

Could you go into more detail here?

I did a bunch of posts on it.
Perhaps you could search this on sbe or, when
I catch up, I'll try to find something.

Tom

--
Cathy

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