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Re: Great Siberian Explosion
A BIG thanks to everyone who cleared up the biologic question, it has been a while
for me! OH, David, wasn't it Boris Karloff andMartin Landau?? :-)
Best wishes,
Matt
Joseph Murakami wrote:
> almitt wrote:
> >
> > Now I can't recall the specifics, but I believe a study by
> > Miller and Urey (UCLA?) created "life" by interacting an electrical charge
> > with the amino acids in a lab. This is the basis of the "primordial soup",
> > out of which life crawled, wherelightening was the electrical charge. Maybe
> > some of our biologists can shed way more light than I can.....
> >
> > Hi Matt and all,
> >
> > I believe that Carl Sagan might have first done something like that at Berkley
> > but who knows if other studies were also conducted later by others. My 2 cents
> > worth anyway.
> >
> > --AL
> >
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>
> Well, here's where a biochemist can contribute something to the list!
> So far, no one's definitely "created life" in a test tube, at least not
> from scratch! Most high school biologists could probably recite
> Miller's early experiment in Urey's lab with electrical discharges
> inside sealed glass enclosures containing a gaseous mixture of methane,
> ammonia, and hydrogen, along with water, thought at that time to be
> representative of the primordial Earth's atmosphere. Imagine Miller's
> delight when he saw the pinkish red tinge of the mixture after a few
> days, especially when the analysis showed the presence of several amino
> acids and other organic molecules typically considered "organic." This
> was an experiment to attempt to simulate "prebiotic" conditions. The
> limited amino acids produced were in equal numbers of optical isomers,
> in other words, a racemic mixture.
>
> Ironically, the conditions and mixture that Miller first contrived are
> now felt not to be respresentative of the prebiotic atmosphere, which
> was probably much less rich with hydrogen. Instead of methane, more
> carbon dioxide is felt to have been present, and instead of ammonia,
> molecular nitrogen was felt to be present. Under these conditions, the
> yield of organic substances fall practically to zero!
>
> Nevertheless, his experiments showed how relatively easy it is to
> assemble organic compounds from prebiotic precursors. Dissimilar
> conditions as occurred in the outer reaches of our primordial solar
> nebula, given any number of sources of energy, could have formed many
> organics readily. The precise pathways for their formations have been
> well studied. As all of us on this meteorite list know, organic
> compounds are found in meteorites, especially our carbonaceous
> chondrites. The Murchison contained a number of amino acids remarkably
> similar to those generated by Miller. The Murchison actually contained
> more than 300 amino acids, not counting their enantiomers. Spectroscopic
> studies of interstellar dust clouds strongly suggest the existence of
> highly reactive combinations of carbon, hydrogen, oxygen, nitrogen, and
> sulfur ...(and silicon)...that suggest similar organic compounds and
> their immediate precursors, like formaldehyde, ammonia, isocyanic acid,
> hydrogen isocyanide, etc., etc. Reflectant spectrometry of asteroids
> and the moons of our gas giants support the red organic albedo's.
>
> Interestingly, there are no aromatic or unsaturated amoino acids in
> meteorites. No benzene rings as in phenylalanine. Even carboxylic
> groups are relatively rare. There's a paucity of sulphur-containing
> amino acids, too. No cysteines or methionines...
>
> Nevertheless, it's been put forth by Armand Delsemme and others that
> virtually all the basic building blocks of life were transported onto a
> sterile degassed Earth by comets.
>
> How these primeval amino acids might have joined together into peptides
> under prebiotic conditions remains a great mystery. In 1951 Theodor
> Wieland discovered how amino acids could be condensed to form simple
> peptides from from amino-acid thioesters, which could themselves form
> spontaneously under reasonable primordial conditions.
>
> Still, it's a huge quantum leap from short peptides to catalyzing
> self-replicating peptides, to a tRNA world, and eventually to
> life...just an incredible miracle! That's the holy grail of
> biochemistry.
>
> As biologist, we've been incredibly fortunate to reverse engineer the
> mechanisms of biology, genetics. And as bioengineers, we've been able
> to "hack" into the machinations of life and attain useful consequences,
> like synthesizing antivirals or cloning or engineering monoclonal
> antibodies. But except for being able to hyjack existing biological
> systems and adapting the principles to our end, we're still light years
> away from manufacturing life from inorganics, not without loading the
> dice by applying advanced organic catalysts to do specific biddings...
>
> So, no one's created life from dust...not yet...
>
> Oh boy, I'd better get some sleep...
>
> Joseph
> Of interest to me was the revelation that there was a L-isomer biase in
> the amino acid make-up of the Murchison.
--
Matt Morgan
Mile High Meteorites
http://www.mhmeteorites.com
P.O.Box 151293
Lakewood, CO 80215-9293
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