Talk:Pyrrolysine

message: Here is a link for the citation needed. 
http://www.chem.qmul.ac.uk/iubmb/newsletter/2009.html#item35
Sorry, I'm not very good at editing and I don't know how to do citations or references  — Preceding unsigned comment added by 140.226.169.99 (talk) 15:06, 16 April 2012 (UTC)
replies: text: Thank you for the suggestion.  I have added it to the article.  -- Ed (Edgar181) 15:12, 16 April 2012 (UTC)
thread_title: Citation

message: There are no doubts why higher organism don't produce pyrrolysine. They produce heme instead, like Porphyrin. Some guys need to do more research about this, so I can read it in the Wikipedia next time. --178.197.236.74 (talk) 16:24, 9 September 2013 (UTC)
thread_title:  Higher organism have heme 

message: "and one known bacterium in enzymes that are part of their methane-producing metabolism."
I would like very much if someone could give a citation that confirms this. It can be bad phrasing, but this make it look like there is at least one bacterium that has the machinery to synthesise methane, which I doubt.  — Preceding unsigned comment added by Januoaxe (talk • contribs) 23:13, 9 November 2015 (UTC)
replies: text: https://en.wikipedia.org/wiki/Methanogen AManWithNoPlan (talk) 00:29, 15 November 2015 (UTC)
thread_title:  Citations needed 

message: Can some table or overview be added to show how frequent pyrrolysine actually is? Currently the article does not state in how many different organisms it has been found. It appears to be extremely rare but we don't know right now because the article makes no comment on the frequency at all whatsoever.  2001:62A:4:31:77:80:42:100 (talk) 20:18, 9 February 2018 (UTC)
thread_title:  Frequency 

message: In arginine and histidine, the nitrogen atom that has less hydrogen atoms beforehand (because it is double-bonded with a carbon atom) gets protonated, so I assume that it would be the same for pyrrolysine, but I'm not sure, and the article doesn't say (although even if it did, it could only be used if the part that said that was cited). I put the SMILES code for each in the SMILES2 parameter of the infobox—but in a comment so they don't show until we can figure out which one is correct. If I'm right and the nitrogen atom with the double-bond (the one in the ring) is protonated, please use the first SMILES code for the SMILES2 parameter. If I'm wrong and the nitrogen atom that's single-bonded to two carbon atoms is protonated, please use the second SMILES code for the SMILES2 parameter. Hopefully, there's a reputable source somewhere that says which gets protonated. Care to differ or discuss with me? The Nth User 19:31, 25 September 2018 (UTC)
replies: text: For histidine, the ring NH nitrogen is the least likely to be protonated because its lone pair is part of the aromatic pi system. The N adjacent to the double-bonded N of arginine and the amide N of pyrrolysine likewise have their lone-pair tied up in resonance with the C=N or C=O pi bond. Resonance effects and hybridization (presence of double bond even if no resonance) far outweigh simple "how many H are already there". A guanidine is substantially more basic than an amine, which is more basic than an imine (the non-protonated N of an imidazole ring has a basicity between amine and imine). DMacks (talk) 01:10, 26 September 2018 (UTC)
replies: text:  I'm confused. Would the nitrogen in the ring be less basic because it is double-bonded to a carbon atom, making it an imine while the other side-chain nitrogen is an amine, or would the nitrogen in the ring be more basic because the other side-chain nitrogen because the other side-chain nitrogen is next to a ketone group, which could tie it up with resonance? Care to differ or discuss with me? The Nth User 02:59, 26 September 2018 (UTC)
thread_title:  Which nitrogen atom in the side chain is protonated?