Why is life on earth made of left handed amino acids?

That would explain why the left hand doesn't know what the right hand is doing.

iVE NEVER BEEN GIVEN A DECENT ENOUGH ANSWER FROM MY COLLEAGUES WHO STUDY THIS, even though wE USE THE RATIO OF l/d AMINO ACID(oops) as a "relative dating" trick. The process is called "RACEMIZATION", in living forms L rotatory amino acids are almost exclusive. However, shortly after death, a living form's amino acids begin to revert back to D rotatory. There is almost an implied log "half life" (WITHIN REALLY BROAD BOUNDS). Its somewhat useful although imperfectly so because each environment adds a little "somethin, somethin" to cause a baseline deviation of the reactions.
As far as the "chiral l problem", My opinion (AND ITS ONLY A WILD ASS GUESS), is that it has to do with the original electronegativity of the Carbon. Remember that from the earliest possible existence of life (3.9 BY ago), the only evidence we have is that C12 was the preferred "Living isotope" because it was ever so slightly lighter and more mobile than C13. I believe that this preferred state was slightly more active and therefore could engage in surface , adsorption reactions and weak force reactions that typify living molecules. I think it had to do with an ever slight ,but significant, ratio that was more bio-active once the first living polymer formed.In other words, once conferred as a living state there was no turning back , and the original C-12 molecules had only a slightly more preferred bio-activity than did others and the combined reactions of life have always (IMHO) included L Aminos, D sugars, and straight phspho -R's .
Remember also that , in the living state . only L- amino acids link to D-sugars. Its a package deal .

Cant help much beyond that since I dont use racemization much because Ive got access to really great isotope labs that dont require as many qualifiers in the way data is handled..Its still an interesting tool though.
If you want to learn more about the development and use of racemization, google up Jeff Bada, Don Wehmiller, Dan Belknap, or Niles Rutter. These guys have used (and matured) the technique that was first discovered by P Abelson back in the early 50's. I think that its a mere fluke of the physical chemical properties of the Carbon and the various enantiomers that are involved in living reactions. We make such a big deal about amino acids but forget that theyd be dead in the water without the phospho lipids and ribose sugars.

Communists are left-handed.

Going back to the old Miller Urey experiments (as amended by Bada and others), we may be looking at the souces of energy available at the origins stage. Maybe L or D polarized light was refracted into the proto atmosphere and the pre-aminos were merely responding chemically.


NO MATTER WHAT-Im certain were gonna hear from the Creationists with Proof Positive as to how this demonstartes without a doubt that life was divinely created by the polarized light emanating through the Big Guys spectacles.

So as an ignorant earth scientist, I have to beg off beyond that which Ive already posted. The CReationists are not similarly bound by personal knowledeg. They will, whether they understand or not, post the latest AIG turds, as scientific "gospel". You watch.
Soon as RL or some others go and drag up some links, they will start jamming the thread with Creationist marmelade. I am fairly certain.

God was busy using his right hand to seed the earth.

You are going straight to hell for that one, DrewDad.

That's where all the interesting people will be, anyway....

D-amino acids are often found in polypetide antibiotics.

Wikipedia

While the occurence of some D aminos acids are there, the vast number of amino acides in the living state are L-rotatory . Its well over 99.99%

I just thought it was an interesting subject. And even if we get spammed with creationist nonsense, the reading necessary to refute the nonsense sometimes leads to a deeper understanding of things.

For example, the investigation of flagella in relation to irreducible complexity didn't reveal an irreducibly complex system, what it did reveal was more detail on the evolution of complex systems such as flagella. This isn't really a surprise by any means, but it's always interesting to see the details of how certain things evolve.

The reason why amino acids are all left handed is completely obvious -- if an organism were born that needed right handed acids, it would not be able to utilize the food from left handed organisms. It can be assumed that, in the early days, organisms in secluded regions had both types...but merged to one over time from evolution. In fact I think there might be one or two organisms on Earth that use right handed...from memory. I haven't look this up, just basing this on my memory from the Feynman Lectures on Physics.

Amino acids found in meteorites are predominately left handed, which strongly implies that the root cause of the predominance in our biology originates not on Earth, but in space.

If that is the case, then the only plausible explanation I can think of is that it is due to the spin of matter (as opposed to antimatter, which has opposite spin and charge).

And the biological implications for micro-organisms and higher forms of life?

What do you mean 'spin' of matter exactly?

As Feynman has pointed out, there is virtually no possible way to distinguish right from left in the universe without having an example to compare to. The only intrinsic thing you could rely upon is quantum mechanical spin.

All regular matter has spin in the same direction. Thus, it may somehow influence the arrangements of atoms in molecules and give a higher propensity of left handed arrangements.

Antimatter (antiproton, positron, etc) is ephemeral in our world only because it is annhilated when it comes in contact with regular matter. But theoretically there could be parts of the universe that are dominated by antimatter...and perhaps in such a region, you would find that amino acids tended to be right handed, because spin was in the opposite direction.

In "earth bound" molecular structure its quite easy to distinguish because we assign stereo-properties. L-or D roptatory amino acids and D rotatory riboribose sugars have specific electro and p-chem properties anywhere on the planet.
However, even in space, we see leucine and iso-leucine and cystine as L rotatory , all clustered around gaseous clouds and Star "nurseries"

Questions for Evolutionists

Homochirality - The problem of left handed amino acids

The problem of homochirality may be summarized by the fact that all of the 20 biologically active amino acids are left handed (apart from one which is so simple that it is neither left or right handed), but that amino acids made in the laboratory are 50% left and 50% right handed. While all proteins are L-amino acids, all sugars are the D form and all nucleic acids in RNA and DNA are the D form.

Why we are made of only left-handed amino acids: the origin of chirality on Earth and in the solar system in beyond ABSTRACT: Most biomolecules are "chiral" or handed, that is to say they exist in two left and right-handed mirror image forms. But biology only uses one hand, i.e. it is "homochiral". One of the greatest puzzles in biophysics is the question of why life on Earth is based on left-handed (L) amino acids and right-handed (D) sugars - why not "mirror life" based on right-handed (D) amino acids and left-handed (L) sugars? The answer may lie in fundamental physics: the parity-violating weak neutral current produces a very slight energy difference between left and right handed molecules, which may become amplified over an evolutionary timescale, and our calculations of this energy difference show that the natural L-amino acids are indeed more stable than their "unnatural" D mirror images. This parity-violating energy difference or "PVED" between mirror image molecules is important not only in biology but also as a "molecular footprint" of fundamental physics: future measurements of the PVED could in effect give us "table-top particle physics", yielding values of the Weinberg angle and other important parameters of fundamental physics much more cheaply with a new generation of spectrometers rather than a new generation of particle accelerators. Homochirality is such a characteristic signature of life that finding molecules all of one hand on other planets could be a signature of life or prebiotic chemistry, and we are building a polarimeter to Search for Extra-Terrestrial Homochirality (SETH) on missions to Mars and other solar system bodies. We are also looking to Search for EXtra-SOlar Homochirality (SEXSOH) by looking for circular polarization in light reflected from planets round other suns in the next century.

We are interested in the origin of biomolecular chirality. Dr Alexandra MacDermott - It is well known that biomolecules are all of one hand, but what determines which hand? Why are animals made of L-amino acids and not D-amino acids? This asymmetry in biology may be a feature of fundamental physics, because it turns out that the "natural" L-amino acids are slightly more stable than their "unnatural" D mirror images, due to the weak force. The weak force, carried by the Z boson recently discovered at CERN, is one of the four forces of nature - electromagnetic, weak, strong and gravity - and it is the only one of the four which can tell the difference between left and right. Due to the weak force, L and D molecules have slightly unequal energies because they are not in fact true mirror images: the true enantiomer of an L-amino acid is the D-amino acid made of anti-matter. We calculate these small energy differences between enantiomers using ab initiomolecular orbital methods. In most cases our calculations do indeed predict the correct sign: not only are the L-amino acids more stable than the D, but the natural D-sugars are more stable than the L, and the right-hand DNA double helix is also more stable than its left-hand mirror image. We believe the slight enantiomeric excess from these "parity-violating energy differences" could be amplified kinetically in the pre-biotic soup to preferentially select today's L-amino acid/D-sugar biochemistry over D-amino acid/L-sugar "mirror life". The parity-violating energy difference between enantiomers is not the only way in which the weak force could select biomolecular chirality. Radioactive beta decay is mediated by the weak force, and this causes a polarization of the electrons emitted in beta decay, which could produce selective destruction of one enantiomer. We are currently starting to develop the theory of this enantioselective beta-radiolysis. Chirality is a characteristic signature of life, and we are collaborating with experimentalists and space engineers to develop a small polarimeter to detect optical rotation as the signature of life on Mars. We also hope to detect the chiral signature of life using polarimetry on the future Darwin space telescopes which will catch light from planets around otherstars: light from an Earth-like planet will show a small circular polarization due to the highly chiral chlorophyll molecules in vegetation cover. Finding molecules of the same hand on many different extra-solar planets would lend support to the weak force theory of the origin of chirality. Some of our team are Co-Investigators on the COSAC experiment of the Rosetta mission, launch 2003, which will use chiral gas chromatography to identify enantiomeric excesses on Comet Wirtanen. We are collaborating with Glaxo Wellcome to use chiroptically detected HPLC to identify chiral molecules in the Murchison and Mars meteorites.

Origin of life: the chirality problem Jonathan Sarfati

Addendum

This NASA article shows amino acids, both flavours, forming in a natural environment, something Miller never accomplished.

This University Science article shows how the flavours of amino acids separate, and promote the evolutionary chemical reactions necessary to begin biological life.

http://ourworld.compuserve.com/homepages/rossuk/question.htm