Forward from ATP (OOL)
- From: TomHendricks474@xxxxxx
- Date: Sun, 29 Jan 2006 13:13:45 -0500 (EST)
Christian de Duve in his book Vital Dust has
some intriguing things to say about the origin.
We both feel that the likely reason for the 'tyranny of A'
is "that adenine happened to be there before the other bases.
It is certainly the easiest one to make abiotically."
(and next is the other purine G - note GTP as 2nd to A
in prime importance.)
He suggests this possibility "ATP, in turn, served
to usher in RNA: in other words information may
have entered by way of ENERGY. What may have happened
is the condensation of 2 ATP molecules to ATP-AMP
with the release of inorganic pyrophosphate. In this reaction, the
2nd ATP donates an AMP molecule to the first ATP,
and the bond between ATP and AMP is sealed at the expense of
the bond that originally existed between AMP and pyrophosphate
in the ATP molecule."
He then goes on to say how this could lead to poly-A tails -
"Unlike the synthesis of true RNA, the formation of poly - A
takes place without the supply of information: it consists merely
of 'dumb,' repetitive assembly."
Then he suggests this aspect - if ATP abundant and PPi scarce
ATP would form poly-A and PPi - "In the opposite situation, excess PPi
would drive the formation of ATP from poly-A
(What would support this is finding a reasonble method of making
abundant ATP through some prebiotic means)
He next suggests a possible scheme for the abiotic formation of
the other 3 bases "an origin from adenine is not inconceivable.
Once they were present, their incorporation into nucleotides
could have been brought about by AMP ... This scenario is conjectural
but not unlikely. It seems reasonable to suppose that the chemistry
came first, without information, and that information came later."
Now it raps up nicely for me and my sun cycle idea when he wonders,
"What the (present day) biological process has (that the) prebiotic
process may have lacked, is a mechanism for the selection of
whichever of the four available nucleotides is to be added at each step.
The birth of this mechanism, which relies on simple molecular
interactions, represents a true watershed in the development of
life on Earth. It signals the transistion from the age of chemistry
to the age of information."
Yet the information inherent in this is - that information that
best sets up a stable chemical response in the sun/heat cycle.
And that would be this
G-C would be more stable than A-U bonds
A-U bonds would be more stable than non W-C bonds -
thus the information inherent in this process
(and that he is looking for) is coding for stability
in that environment.
Comment
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