Talk:Cyclic guanosine monophosphate

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Chemical structure of cyclic guanosine monophosphate

I've removed this structure from the article because it is quite incorrect. The guanine is shown in a rare tautomeric form, and what should be the phosphate P is shown bonded to another P. Josh Cherry 22:20, 3 Jul 2004 (UTC)

See, if we had wikitex turned on right now, fixing something like this would be a matter of simply editing a few lines of text, instead of drawing the whole diagram again. It's in the distribution; I don't know why they haven't enabled it. grendel|khan 02:33, 2004 Jul 4 (UTC)

Zoinks. Thanks for catching the error. I had copied the structure directly from ChemFinder.com, which I had (until now) understood to be a good resource for chemical structures. Regardless, I've modified the structure and uploaded the new version. I haven't checked my chem/biochem or molecular bio books, but a quick Google search suggests that this is the consensus. I wonder, however, as to whether the negative charge on that phosphate should in fact be on one of the sp² oxygens instead... --Diberri | Talk 22:42, Jul 21, 2004 (UTC)

OK, I'm happy to look at the new structure, but where is it? Josh Cherry 23:44, 21 Jul 2004 (UTC)

I see it now (I was seeing the old one originally for some reason). With respect to the phosphate, that's one way to draw it, but another, I think more standard and preferable way is to put the negative charge on one of those oxygens and get rid of the double bond between the phosphate and that oxygen (moving the charge and but leaving the double bond would be incorrect). Yet another way to draw it is to get rid of both double bonds, put negative charges on both oxygens, and put a positive charge on the phosphorus. That's actually a more accurate depiction of what's going on, but rarely seen. Josh Cherry 23:57, 21 Jul 2004 (UTC)

You were seeing the old version because it was in your browser's cache. Ctrl-F5 is your friend. Browser issues aside, I decided to move some electrons from one of the P=O bonds to the oxygen atom, giving it a negative charge and leaving the phosphate neutral. I haven't seen a drawing of cGMP with a positively charged phosphate bonded to two negatively charged oxygen atoms. IIRC (organic chemistry was a while ago), while there's definitely some equilibrium between the two states (i.e. P with O^- and P⁺ with two O^-), I'd think that it'd disfavor a separation of charge, and thus the neutral P with negative O would be more prominent. But perhaps that's fallacious. I am not a chemist :-) --Diberri | Talk 01:41, Jul 22, 2004 (UTC)

It's a resonance rather than an equilibrium. My understanding is that in fact there is a large contribution of the charge-separated resonance form. The P and the O are essentially connected by a single covalent bond plus an "ionic bond" (and to the extent that there is a second covalent bond, it's not a conventional pi bond, but involves d-orbital overlap). But it's rarely drawn that way, even if it should be; I agree that the way you have it is the right way for an encyclopedia. Josh Cherry 02:00, 22 Jul 2004 (UTC)

Nice to see that you have included Jacky Corbin as your only reference. He is probably the only one who didn't made money from the Viagra hype. Nice/wise guy. Keep it. (anonymous cG-guru) --80.133.106.113 00:48, 10 Aug 2004 (UTC)

Hyperpolarisation?

I quote:

degradation of cGMP causes calcium channels to close, which leads to the hyperpolarization of the photoreceptor's plasma membrane and ultimately to visual information being sent to the brain

IMHO, hyperpolarisation lowers the chance of a spike and subsequently of any info being sent. Maybe I'm mistaken here, but anyway, that caught my attention. Best regards, --CopperKettle 16:00, 11 October 2009 (UTC)[reply]

Wiki Education assignment: CHEM 378 - Biochemistry Lab - spring 2023

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