Posted on 02/03/2006 10:23:55 PM PST by neverdem
For those who are studying aspects of the origin of life, the question no longer seems to be whether life could have originated by chemical processes involving non-biological components but, rather, what pathway might have been followed.
National Academy of Sciences (1996)
It is 1828, a year that encompassed the death of Shaka, the Zulu king, the passage in the United States of the Tariff of Abominations, and the battle of Las Piedras in South America. It is, as well, the year in which the German chemist Friedrich Wöhler announced the synthesis of urea from cyanic acid and ammonia.
Discovered by H.M. Roulle in 1773, urea is the chief constituent of urine. Until 1828, chemists had assumed that urea could be produced only by a living organism. Wöhler provided the most convincing refutation imaginable of this thesis. His synthesis of urea was noteworthy, he observed with some understatement, because it furnishes an example of the artificial production of an organic, indeed a so-called animal substance, from inorganic materials.
Wöhlers work initiated a revolution in chemistry; but it also initiated a revolution in thought. To the extent that living systems are chemical in their nature, it became possible to imagine that they might be chemical in their origin; and if chemical in their origin, then plainly physical in their nature, and hence a part of the universe that can be explained in terms of the model for what science should be.*
In a letter written to his friend, Sir Joseph Hooker, several decades after Wöhlers announcement, Charles Darwin allowed himself to speculate. Invoking a warm little pond bubbling up in the dim inaccessible past, Darwin imagined that given ammonia and phosphoric salts, light, heat, electricity, etc. present, the spontaneous generation of a protein compound might follow, with this compound...
(Excerpt) Read more at commentarymagazine.com ...
It does if the origin of life corresponds to one of the major world religions, and most, if not all, of the minor ones.
To say that Christianity, Judaism, and Islam are compatible with evolution is simply to be ignorant of what these texts teach....however wishful and compromising your thinking may be.
Those of us who consider logic and reason to be a beneficial attritbute of the human condition, do not agree with your inference that evolution is compatible with all possible scenarios. Such thinking just reinforces the observation that evolution is an unfalsifiable concept...and it does nothing to garner intellectual respect from those who should be your audience.
That you believe evolution to have occured is implicit from your writings. That evolution must necessarily occur, is simply not dictated by logic.
Considering that only single bonds can be excited, and excitation of those bonds doesn't depend on the optical rotation of incident light, there can be no effect.
I don't know where that post was, but racemization requires bond breaking.
Ahh, *that* part I missed. Thanks!
I never heard of the Discovery Institute outside of these threads. Are they perhaps in general rather late at catching up to things? Oh--I get it--they are so late, so often, that you think it is *deliberate*. Like some of the more (in)famous crevo posters here.
Cheers!
Optical rotation is quite complex and is affected by pH and concentration. In addition, the pK of groups like sulfhydryl groups affect the rotation. A big pH change can even shift one from a + rotation to a - rotation.
Here are the rotations, usually at 20 C, but the concentrations and pHs vary because of solubilities:
L-ala +2.8
L-arg +26.9
L-asp +25
L-asn -5.4
L-cys +13
L-cystine -223.4
L-met -8.2
L-glu +31
L-gln +6.1
L-pro -52.6
L-leu -10.8
L-lys +25.9
L-his -39.7
L-thr -28.3
L-ile +11.3
L-val +13.9
L-ser -6.8
L-trp -31.5
L-tyr -10.6
L-phe -35
L-hydroxyproline -76.5
L-ornithine +11.5
L-citrulline +3.7
achiral: glycine, beta-alanine
I'm sure I missed some - list from Merck Index.
should have pinged you guys too.
Darwin would have researched it further
Enzymatically converted - yes, but not post translation. The peptidoglycan is not a translated protein.
I don't think these biological molecules came from space anyway. I think the L amino acids are the only ones that have a significant interaction with RNA triplets, as per RWP's post above. I haven't looked at it, so it's quicker to ask RWP if that's so. RWP?
I invite the lurker to look at the article Berlinski wrote, a supposed survey of the current status of abiogenesis research, and ask himself whether Behe should have known of this link (or at least the various article footnoted therein) or, if not this link (admittedly local in origin, at least the papers cited therein, specifically:
But if you want geochemical differences in precambrian rocks that indicate the presence of a reducing atmosphere, see for example Geological and trace element evidence for a marine sedimentary environment of deposition and biogenicity of 3.45 Ga stromatolitic carbonates in the Pilbara Craton, and support for a reducing Archaean ocean (2003) by Van Kranendonk, Webb, and Kamber. Excerpt from the abstract:Berlinski should know this. He in effect claims not to. But what he conveniently does not know seriously undercuts his premise and he has no business writing the lead article of this thread without knowing the actual state of the evidence for a reducing atmosphere. How does that rate a big *sigh* over my pointing this out? Why is the bar set so low for the Holy Warriors of the un-Discovery Institute?The geochemical results, together with sedimentological data, strongly support: (1) deposition of Dresser Formation and Strelley Pool Chert carbonates from Archaean seawater, in part as particulate carbonate sediment; (2) biogenicity of the stromatolitic carbonates; (3) a reducing Archaean atmosphere; (4) ongoing extensive terrestrial erosion prior to 3.45 Ga.A "reducing atmosphere", for those in Rio Linda, is "An atmosphere of a planet or moon which has a high hydrogen content, either in the form of free hydrogen or hydrogen-containing compounds, such as methane or ammonia", according to the Encyclopedia of Astrobiology, Astronomy, and Spaceflight.
That wasn't really the point I was making. I may be wrong (and I'm sure S will correct me if I've got it wrong) but, as I understand it, S is arguing against the notion that polarized light can destroy different isomers at different rates. S says that only the interaction of the light with the individual bonds is important and, because the molecules are randomly oriented to the light, the light won't be able to tell the difference.
I think that argument is suspect because solutions of molecules homogenous in chirality do interact differently depending on polarization.
You mean I done been flim-flammed on this purchase? :-)
As long as you sleep on your right side, it should work fine:)
Those Killer Bs, they got me this time! Berlinski is at issue here.
The photodestruction of a compound is going to depend mostly on the light intensity and the wavelength. RWP may have something to add here.
It's the configuration that causes that, not the dielectric response causing rotation.
I think you mean wavelength only - the intensity would affect the rate but it's the frequency that selects the interaction.
Again, it seems to me that photodestruction is simply one kind of interaction if light and matter and that if another interaction depends on chirality then perhaps photodestruction can too in the right circumstances.
Of course I'm seriously out of my depth here :-)
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