"TomHendricks474"  wrote in message 
news:cjdga8$1et6$1{at}darwin.ediacara.org...
>I don't think that it is a coincidence that nucleic
> acids absorb light strongly in the UV range, or that
> they do so in this order (from most to least) A,G,U,C
>
> "...bases and all of their derivatives (nucleosides,
> nucleotides, and nucliec acids) absorb light strongly
> in the near UV region of the spectrum..."
> Biochemistry, van Holde, Matthews.
>
> The text shows a chart of"UV Spectra of
> Ribonucleotides or
> what each of the 4 bases
> absorbs, and where they absorb the most. Note the
> order from highest absorption to lowest:
> A - 260 nm
> G - 250 nm.  then a noticeable drop
>
> U - 260 nm
> C - 270 nm.
>
> Note that A and G are both purines. I have suggested
> that perhaps a 'purine' world preceded the RNA world.
> Note that U is the 3rd highest, and C the fourth.
> I have also suggested that U may have been the first
> to add to the purine world, and C the last to.
>
> I can't say WHY there is a correlation between
> absorption and the start of life. But I think this
> and other factors hints that this is the right
> direction to explore:
>
> 1. Life as a thermaldynamic system (with
> replication a novel form of energy moderation)
> 2. Life is a reaction to the sun/heat cycle.
> 3. Ribonucleotides absorption of UV
> 4. Pyrimidine dimers that may have given
> a  more stable advantage to the purines.
> 5. UV does the same as lightning in Miller-Urey
> experiments.
>
> Comment?

If UV was the critical factor driving the sun-heat cycle hypothesis, it 
would have to be responsible for the cleaving of the RNA strands during the 
day, leaving the sequence intact for the night, while the strand picks up 
it's complementary nucleotides during the night.  Does your hypothesis 
account for greater stability under UV for the strand vs. the link between 
strands?
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 10/1/04 5:29:37 PM