Talk:Peptide nucleic acid

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Just out of curiosity, i've never heard of PNAs as progenitor molecules... any good papers on the subject? Graft

I read it in Scientific American quite some time back, and it stuck in my head. Searching... here, I think this is the one:

The Origin of Life On Earth; October 1994; by Orgel; 8 Page(s) Growing evidence supports the idea that the emergence of catalytic RNA was a crucial early step. How that RNA came into being remains unknown.

The issue itself is filed away somewhere in a box that will take me a lot of work to dig out, so unless you don't have access to a local copy I'd prefer not to. The article might have a reference to a better paper than a scientific american article, hopefully. Bryan

Wow! Great stuff! Thanx for an article that broadens my universe!

I was immediately inspired to revise my family tree. There are now 3 nodes at the root: The PNA World, The RNA World, and Biota (or should it be Eubiota?) The first two items are flagged "hypothetical", "extinct" and "supposed precursors of all Biota".

Critiques: The technicalities are simply too overwhelming for the general reader. I won't comprehend the structure in the 1st paragraph without a diagram. Shouldn't it be a goal to present all molecular structures both as diagrammed formulas and as objects rotating in a reader-controlled panorama? (The technology exists, I think, but the work here is daunting.)

The 1st sentence in the 2nd paragraph is fine, but the rest of this 'graph is incomprehensible to a general reader (the sin of unexplained jargon). Wouldn't it be enough, comparing reactivity and stability, to say, for example, that double helix DNA comes apart at temperatures 20 Celsius lower than double chain PNA?

Are there such things as PNA catalysts (analogous to enzymes and ribozymes)? This would be of great significance for evolution.

If the PNA and RNA Worlds existed simultaneously, it is clear that PNA's lower reactivity and greater stability would allow the RNA World to gobble it up.

Could one say [gasp:anthropomorphic] that RNA still rules today, using DNA as a convenient, slowly mutating, copyable information store? If there were CPUs in the cell, would they be ribozymes? I see the ribosomes and some of the other things as distributed processors.

  Solo Owl 01:42 Nov 4, 2002 (UTC)

It is true that some researchers have proposed that PNAs were progenitor molecules, but I don't think anyone actually takes that claim seriously. There is absolutely no evidence that PNAs ever existed outside of the lab, unlike RNA for which many natural ribozymes are known.

the addition of that part is unnecessary to the lead sentence. PNA does not exists in nature. Full stop. Why add the qualifier "present life"? With the same reasoning, endless strings of qualifiers may be added: in present life, nor on Venus, Mars, the moon Europe, nor in the past, but maybe in the future ......... Let's stick to the facts and do not load a simple sentence with wishful thinking, OR and POV. Northfox (talk) 11:12, 6 February 2008 (UTC)[reply]

PNA may very well have been present in past life on Earth. Since no life has been discovered on those other planetary bodies, your attempted WP:OTHERSTUFFEXISTS is specious. The reason PNA was proposed in various abiogenesis models is because it may have been a starting point for life. Not "OR" or "POV" required. ScienceApologist (talk) 15:09, 6 February 2008 (UTC)[reply]

the hypothesis that PNA was a precursor for RNA and DNA is there, for sure. But this is discussed in the abiogenesis sections of various articles, including this one. Point is that there is no reason to have this strange construct incorporated in the lead sentence. Why single out PNA and GNA, as the compounds that might have existed and are now 'extinct'? There is no proof that they existed anytime, anywhere. By using the same reason (might have existed) one could easily to add the 'in existing life on Earth ' part to all articles describing non-natural and artificially synthesized chemical compounds. Since this is nonsense, I would prefer to be consistent and remove the 'in existing life on Earth ' part here, too.

Northfox (talk) 04:14, 7 February 2008 (UTC)[reply]

Not quite. The very reason that these molecules are notable is because they are used as possible models for abiogenesis. Your argument would apply if the molecules were notable for other reasons, but since this is how they derive their notability, we are right in characterizing them as absent from present life only. The removal of "in existing life on Earth" is (perhaps no-so-)subtle creationist POV-pushing, as is the request for "proof" which is something that science never offers anyway. We are here to report why things are encyclopedic. This provides a proper framing of the subject. Other compounds that are subject to speculation and are notable for being subject to such speculation should also be so characterized. ScienceApologist (talk) 18:26, 8 February 2008 (UTC)[reply]

the encyclopedic value of PNA is its significance in biology and medicine, as amply stated in the text. The hypothesis that PNA played a role in abiogenesis is also amply - and justifiedly so- mentioned in its own paragraph. I completely fail to see how the removal of the sentence fragment in the lead could be seen as "creationist POV pushing". Such a fragment would only make sense if there was proof, or a very strong supportive information that in the past PNA would have existed in nature. This is not the case, and this is point is correctly summarized in the text of the article. Thus I revert again. Northfox (talk) 14:18, 9 February 2008 (UTC)[reply]

Again with the "proof". The speculation of this molecule is what makes it notable. We keep this clause in as an indicative caveat. ScienceApologist (talk) 17:54, 10 February 2008 (UTC)[reply]

I mentioned not only "proof", but also "supportive information" to keep this in the lead sentence. The notability in a hypothesis about abiogenesis is stated in the main text. That is sufficient. Northfox (talk) 23:42, 10 February 2008 (UTC)[reply]

The lead summarizes the ideas that are most important. ScienceApologist (talk) 14:25, 11 February 2008 (UTC)[reply]

unindent. From the same lead aricle: "The lead should not "tease" the reader by hinting at but not explaining important facts that will appear later in the article." The fragment 'not known in modern life' hints that it was part of the biosphere in pre-modern life (whatever that you imagine that to be). Fact is that PNA is not part of life as we know it. And we don't know any other life forms. So we can only speculate about it. And we do so in the related paragraph furthe below. PNA is notable for very real medical (and related) research, not for a hypothetical precursor of RNA or DNA. Northfox (talk) 11:35, 12 February 2008 (UTC)[reply]

I took the liberty to change the lead sentence. Biggest reason was that the 'but' makes the wrong connection. In the previous version, it modified 'modern life forms', but logically it should modify the 'occur naturally', by contrasting it to 'artificially synthesized'. Since User:ScienceApologist kept reverting me, I chose a different, more logical, order of statements. Also, "polymer" is better than "compound".Northfox (talk) 08:23, 17 February 2008 (UTC)[reply]

quick addendum: we need to define 'modern life forms' here. There is no 'modern life' wikiarticle. Anybody with a good outside link?Northfox (talk) 08:26, 17 February 2008 (UTC)[reply]

http://www.sciencedaily.com/releases/2012/11/121110093550.htm — Preceding unsigned comment added by Jjknack1 (talk • contribs) 22:24, 11 November 2012 (UTC)[reply]