Biological homochirality: A curious case of left-handed amino acids
2009 March 21
The problem of amino acid homochirality can be summarized by the fact that abiotic synthesis of amino acids roughly produce equal mixtures of left-handed and right-handed types, but in biological setting all of the 20 active amino acids are left-handed type. A similar but opposite behavior is observed for nucleic acids where they have preference for right-handed structures. Homochirality is a unique property of living matter and it gradually disappears after the death of living matter which indicates that origin of homochirality may be related to the origin of life. There appear to be no established reasons why left-handed amino acids should be favored over right-handed amino acids in biological systems. Over the time scientist believed that the amino acids isolated from interstellar space meteorites have approximately equal mixtures of left-handed and right-handed molecules. According to a recent study published in PNAS, Glavin and Dworki reports that for meteorites older than earth the ratio of amino acids is tilted toward left-handedness. They also suggest that
the origin of life on Earth and possibly elsewhere in our solar system was biased toward L-amino acid homochirality from the very beginning.
Glavin further suggests that
Meteorites would have seeded the Earth with some of the prebiotic compounds like amino acids that are needed to get life started, and also biased the origin of life to the left-handed amino acid form,
Coauthor Dworkin says that
If we find the life is based on right-handed amino acids, then we know for sure it isn’t from Earth. However, if the bias toward left-handed amino acids began in space, it likely extends across the solar system,so any life we may find on Mars, for example, will also be left-handed
Based on study carried out over six different meteorites specimens each one with different amounts of water, they discovered that meteorites with more water also had greater amounts of left-handed isovaline. Glavin suggests that
the process might have started when the amino acids made contact with melting ice inside the meteorites’ parent asteroids–water tends to help left-handed amino acids multiply and dominate.
Few scientist suggest that these new findings may be resulted due to possible contamination.
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Biological homochirality: A curious case of left-handed amino acids: The problem of amino acid homochirality can.. http://tinyurl.com/cghfcu
Does anyone have an opinion on whether a cell could survive with only D amino acids?
The problem of biological homochirality is explained here…
http://aetherwavetheory.blogspot.com/2008/11/cp-invariance-violation-and-chirality.html