Talk:Cooperativity

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I am very uncomfortable with this article. In particular the two last paragraphs are entirely wrong. First, unwinding of nucleic acid is precisely not a cooperative process. Nucleic acid dissociate as zippers. The stability is controlled by the identity of the adjacent nucleotides, that we call the Crick's pair. The stability of a duplex can be calculated by a linear combination of the free energy of all the Crick's pair it contains. Although the melting curve shows an abrupt transition (a sigmoid curve), it is not due to an energy linkage between the different nucleotides. See Le Novere. Bioinformatics. 2001 Dec;17(12):1226-7 and reference therein. Second, the cooperativity of oxygen binding to hemoglobin has not much to do with entropy. The role of statistical binding and progressive increased affinity (Adair-Klotz or Koshland models) has been abandoned a long time ago for hemoglobin. We know that hemoglobin exists under two different, interconvertible, conformations, with different affinities for oxygen. And the cooperativity comes from this difference of affinity (enthalpy, not entropy) and the fact that the monomer are linked (they tend to be in the same conformation). Nicolas Le Novere (talk) 11:08, 20 May 2008 (UTC)

I agree with the above poster about the entropy section. Unfortunately I'm not an expert on the subject, but the lecture notes and textbook I have in front of me both describe cooperativity of h(a)emoglobin in terms of conformational changes as deoxyhaemoglobin changes to haemoglobin. Deoxyhaemoglobin is square pyramidal containing the Fe(II) ion, whereas oxyhaemoglobin is octahedral and contains Fe(III). The change in oxidation state of the iron ion reduces its ionic radius and allows it to move upwards into the porphyrin ring.

Well, I suppose if no one gets round to editing this beforehand, I'll make the edits once I've got my coursework back. Don't want to be accused of plagiarism for putting my own work up on Wikipedia! Baratron (talk) 19:56, 15 April 2009 (UTC)

I think it would make sense if this article started from more fundamental statistical mechanics concepts. Cooperative binding is just one type of cooperativity. I would call any sigmoidal thermodynamic transition cooperative, with phase transitions as the limiting case. Protein folding, for example, is also a highly cooperative process in many cases. Furthermore, I can't see why there is anything wrong with describing DNA unwinding as cooperative, this should in most aspects be analogous to protein folding/unfolding. A good starting point for this article could for instance be the Zimm-Bragg model for helix-coil transitions and the MWC model for cooperative ligand binding. Mittinatten (talk) 10:29, 10 January 2011 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Cooperativity/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

I second the above comments -- this article is completely wrong in a number of ways. It confuses statistical effects with true cooperativity. In the case of hemoglobin, there is a statistical effect that would be expected based on the 4 hemoglobins / 4 possible oxygen combinations, but there is an additional energetic effect where the binding of one molecule of oxygen leads to a change in the energetics of binding a second molecule of oxygen. Cooperativity refers to this second phenomenon. At the very least, it would be nice for the article to explain the difference between these two phenomena. I don't have any references handy, but I might stop back to fix it later.

Last edited at 20:53, 13 December 2008 (UTC). Substituted at 12:15, 29 April 2016 (UTC)

Merger Proposal

This article Cooperativity has significant overlap with Cooperative binding. There are clearly different ideas about how the concept should be defined and described, but these have not been acknowledged or addressed in the article. Jzpearson (talk) 09:17, 26 January 2018 (UTC)