Scientists find life in Milky Way center
March 26, 2008No, we didn’t really find life, but newspapers tend to go with headlines like that, so why can’t I?
Anyways, scientists have found an organic molecule closely related to amino acids near the center of the Milky Way. From the release:
Researchers from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn have detected for the first time a molecule closely related to an amino acid: amino acetonitrile. The organic molecule was found with a 30 metre radiotelescope in Spain and two radio interferometers in France and Australia in the “Large Molecule Heimat”, a giant gas cloud near the galactic centre in the constellation Sagittarius (Astronomy & Astrophysics, in press).
Phil Plait picked this up and will give you the low down. I’m interested in something else though.
I wrote about exoplanets the other day, and mentioned my cousin asking if alien life would really need water as opposed to some other liquid. So I wonder, does alien life need the same amino acids as we use, or might they use a different set? Maybe the use right handed instead of left handed amino acids. Or perhaps they use amino acetonitrile and other molecules closely related but different from our own amino acids.
I am just wondering aloud here, as this is far from my area of knowledge, but it would be nice to get an answer from someone who knows more about it.
I would speculate that life would need water (but I could be wrong) but most of the other molecular building blocks that we use are probably optional. It is thought that during the molecular evolution that preceded the appearance of life many different molecules were present that are not used by life now. For instance, DNA uses the sugar deoxyribose in the backbone of the molecule, but it might be you could come up with a molecule that does the same job DNA does (storing information) while having a different sugar. Perhaps easier to change would be the bases on DNA. Why use guanine, adenine, thymine, and cytosine? We have made synthetic DNA with non-natural bases in the place of these, so there’s no reason to think no other possible set would work but these four.
With the amino acids I wouldn’t be surprised if some would show up in alien life because they are so simple, but certainly novel amino acids could be used too. While a set of standard amino acids are used to make proteins, sometimes organisms modify these amino acids to convert them to non-standard amino acids afterwards, and one type of archaea have actually sorted out a way of using a stop codon to code for the non-standard amino acid pyrrolysine during protein synthesis.
The handedness of molecular buiding blocks is also not required. Most of your enzymes would not do too well if suddenly faced with a substrate with the wrong handedness, but if you’re building life from the ground up you can probably use whichever handedness convention you like as the pieces will all evolve together.
In some cases multiple options were probably present originally and the one we ended up with survived because it was the best option. In other cases the molecules we use are probably due to a “frozen accident” where one molecule happened to predominate without having any real superiority over the alternatives.
If you are interested in this topic you might check out De Duve’s book Singularities: Landmarks on the Pathways of Life. It’s pretty technical but you could probably pull some really interesting ideas out of it.
Thanks for the answer. The amino acids (or other building blocks) used by alien life forms would be quite an interesting thing to know. If we ever find ET and figure out how to drop by for a visit, his cattle might not be able to provide us with the essential amino acids…
I was also pondering why left handed amino acids dominate, but found my own answer:
http://www.newscientist.com/article.ns?id=mg19025545.200&feedId=online-news_rss20