Eurekalert has a press release from Yale proclaiming that:
Chemists at Yale have done what Mother Nature chose not to -- make a protein-like molecule out of non-natural building blocks, according to a report featured early online in the Journal of the American Chemical Society.
Nature uses alpha-amino acid building blocks to assemble the proteins that make life as we know it possible. Chemists at Yale now report evidence that nature could have used a different building block - beta-amino acids -- and show that peptides assembled from beta-amino acids can fold into structures much like natural protein.
What's going on here is that they've, taken molecules that aren't the amino acids we normally use, and, um, made molecules from them that sort of look like proteins. I think. Really, I've got nothing, here-- this is far enough out of my field that I don't really know what they're talking about, and the more technical news story might as well be in Urdu for all the sense I can make of it.
This caught my eye because of past speculation about quantum information-- back when I was still on Usenet, I remember some people making a big deal out of the fact that there are only twenty amino acids in use in nature, and twenty happens to be the maximum size of a search space for Grover's algorithm for some small system size. This led to some Penrose-ish speculation that life is inherently quantum, with proteins being assembled efficiently by some sort of quantum enhancement.
This always struck me as little more than numerology, but it was certainly a memorable idea. I tend to be reminded of it when I see articles like the press release linked above. I have no idea what the implications of this result for that theory (or vice versa) would be, but I thought I'd highlight the article anyway. Maybe one of the many bio/chem types running around here can make more sense of it than I can.
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Chad - You might have enhanced your reference to numerology by noting that those twenty amino acids have long been known as the "magic twenty."
There are 64 "codons" each consisting of three pairs of nucleotides. These map onto the "magic 20" amino acids (that being the number for humans, there are some other amino acids for other organisms) plus "start" and "stop" instructions. The mapping is degenerate, with more than one codon for the same amino acid, and more than one way to say "start" or "stop." So it is indeed handwaving numerological incantational nonsense, invoking St. Grover's name in vain, to pretend that this is smack up against some sort of limit. You know, like Penrose saying that consciousness depends on nonlinearities in the relativistic Schrodinger equations (Dirac equations?) for the wave function of the human brain. Or folks from Indianpolis claiming that Super Bowl XLI was divinely inspired because it has a prime index (41), each team ended with a prime score, and the first play was the touchdown return of kickoff by player #23...
Or folks from Indianpolis claiming that Super Bowl XLI was divinely inspired because it has a prime index (41), each team ended with a prime score, and the first play was the touchdown return of kickoff by player #23...
But that's just common sense, we already know 23 is a magic number!
(Insert /sarcasm tag for the impaired.)
What's going on here is that they've, taken molecules that aren't the amino acids we normally use, and, um, made molecules from them that sort of look like proteins. I think.
Essentially that's right. These folks are using building blocks that are slightly (one C atom) longer than the usual (alpha) amino acids. These building blocks have been strung together into long chains (proteins are just long chains of amino acids), and the researchers have discovered that the shapes formed by these new (beta) amino acid chains are reminiscent of, but not identical to, those of alpha-amino-acid-based proteins.
*Shrug* I'm sure it's great work, but it would have been much more exciting science if they hadn't seen essentially the same chemistry as one gets with "normal" proteins. That said, functionality in biochemistry is all about shape, so the ability to make new shapes could have huge benefits.
Grant's got it. The work is sort of a proof-of-concept (proteins probably look like they do because alpha-aa were the building blocks that happened to be around way back when chemistry was becoming biology; it could have been other, similar molecules) and also a step towards designer proteins with novel properties (such as therapeutics, or models for understanding natural proteins).
It's cool and all, but not really a big honkin' deal. It was sort of an obvious thing to do, and the results are pretty much what you'd expect.
Actually, a lot of that numerology is a reminiscence of the theories developed about the genetic code, before the code was determined. Nature has never being forgiven for turning out to be so arbitrary, when beautiful theoretical models predicted the numbers so well. For a nice outline of those theories (from which Gamow's "diamond code" is probably the best known) check Brian Hayes' short article "The Invention of the Genetic Code" (note: invention, not discovery), available here.
I'm pretty sure there are 22 naturally encoded amino acids. I believe the discoveries of 21 and 22 were published in Science.
Yep Tela, in fact, there were 23 the last time I knew, and there are probably a few more to be discovered. The most common is selenocysteine. Usually some stop codon has been redirected to code for the additional aa, and in general there is some kind of "longer signal" (something in the sequence, beyond the codon itself) telling the molecular machinery to make the exception there. Thus, even in these cases the universal code has been more or less kept.