TNA

[arcticpenguin]

http://www.nature.com/nsu/030203/030203-1.html

DNA polymerase, that copies chromosomes before a cell divides, will duplicate a synthetic molecule called threose nucleic acid - TNA - Jack Szostak and his colleagues at Harvard General Hospital in Boston have found.

For those who don't remember, DNA is deoxyribonucleic acid.

[rwald]

I'd like to see a structural diagram of threose vs. ribose and deoxyribose. Anybody know where one can be found?

[Soapy Sam]

Well, you can stir paint with a screwdriver. Maybe we'll find there are a bunch of possible places DNA polymerase will function. Perhaps other parts of the DNA/RNA machinery as well.
Possibly early on, the best general purpose machines were the most successful, but the pool of what they worked on was then whittled away by natural selection? Be interesting to see what else this line of research turns up.

[gmol]

Originally posted by rwald
I'd like to see a structural diagram of threose vs. ribose and deoxyribose. Anybody know where one can be found?

Google Images is a good place to enter in molecule names to get pictures of structures.

[gmol]

This is the first time that I know that someone used a different sugar instead of a different base...using unnatural bases is harder since those are the recognition elements.

While polymerases are specific, like all enzymes, you can always make a molecule that you can trick the enzyme into thinking it is its' natural substrate. There are many examples of nucleic acid analogues that you can co-erce into working with particular types.

Your theory of general polymerases (while fun to think about) doesn't jive with the surrent standard model of molecular evolution (not to say that it is right)....

It seems like there were probably RNA based polymerases (i.e. not made out of protein) that recognized RNA (and RNA like things). Then came ribosomes...then we got protein synthesis and somewhere later DNA came into the picture. Thus far, there has been no evidence of a large diversity of naturally occouring nucelic acids. The oldest archea that we know still use DNA and RNA...

Originally posted by Soapy Sam
Well, you can stir paint with a screwdriver. Maybe we'll find there are a bunch of possible places DNA polymerase will function. Perhaps other parts of the DNA/RNA machinery as well.
Possibly early on, the best general purpose machines were the most successful, but the pool of what they worked on was then whittled away by natural selection? Be interesting to see what else this line of research turns up.

[Jon_in_london]

Im unable to post images at the mo' maybe someone could kindly post threose and ribose to compare. Im not really that suprised that DNA pol. will copy this TNA stuff but what amazes me is that they can get a TNA polymer at all since there isnt any 5'-CH2OH group to form a phosphoester bond :confused:

Originally posted by rwald
I'd like to see a structural diagram of threose vs. ribose and deoxyribose. Anybody know where one can be found?

diagrams (http://pubs3.acs.org/acs/journals/toc.page?incoden=jacsat&indecade=0&involume=125&inissue=4)

Cheers,

[rwald]

Thanks, Bill. One minor question: In those diagrams, it seems that there's one O that is bonded to the P once, but which has a second bond leading to nothingness. Is that supposed to be an OH bond? Or is it a minus, indicating that the O has more than its normal share of electrons (which wouldn't make sense, because it appears to only have 7 valence electrons, not 8). For that matter, the B's stand for Bases, not Boron, right? Thanks for your help with this.

Originally posted by rwald
Thanks, Bill. One minor question: In those diagrams, it seems that there's one O that is bonded to the P once, but which has a second bond leading to nothingness. Is that supposed to be an OH bond? Or is it a minus, indicating that the O has more than its normal share of electrons (which wouldn't make sense, because it appears to only have 7 valence electrons, not 8). For that matter, the B's stand for Bases, not Boron, right? Thanks for your help with this.

In the TNA / DNA diagram, the B's do stand for the bases. Not to be confused with the diagram immediately below, where B means boron. The downward-pointing dash is supposed to indicate the 3' end, the upward-pointing dash is supposed to indicate the 5' end.

Cheers,

[Soapy Sam]

"The oldest archea that we know still use DNA and RNA..."

Gmol, I'm not sure exactly what you mean by this.
1. The oldest fossil Archaea appear to have used DNA/RNA
2. Things alive today and classed as ("simple and ancient") use DNA/ RNA. (Me, for instance).
or something subtly different.

[gmol]

Bacteria, alive today, which fall under the kingdom archea, which by most (all) evolutionary metrics appear to be the closest to the common 'root' of the 'tree of life' use DNA and RNA.

Originally posted by Soapy Sam
"The oldest archea that we know still use DNA and RNA..."

Gmol, I'm not sure exactly what you mean by this.
1. The oldest fossil Archaea appear to have used DNA/RNA
2. Things alive today and classed as ("simple and ancient") use DNA/ RNA. (Me, for instance).
or something subtly different.

[zakur]

Originally posted by gmol
Google Images is a good place to enter in molecule names to get pictures of structures. But if you're going to do a search on "TNA" make sure you have their SafeSearch turned on. Unless, of course, you don't mind looking at a lot of the other kind of t-n-a. ;)