Talk:Histidine

message: The 3D structure shows the amino acid as an uncharged molecule but it should be rather present as a zwitterion. Also the IUPAC name and formula are not for the endogenous amino acid but the racemate of R and S histidine. Is it on purpose or should I change it?
-- Panoramix303 (talk) 19:16, 23 March 2008 (UTC)
thread_title: 3D structure

message: I deleted some of the content from this section diff as the content made rather extraordinary and sweeping claims that would need good citations to remain. Tim Vickers (talk) 21:50, 2 April 2009 (UTC)
thread_title: Supplementation

message: The article does not mention whether histidine is synthesized in the body from some other precursor substance or is itself a commonly occurring amino acid in food.  —Preceding unsigned comment added by Carusus (talk • contribs) 11:19, 16 May 2010 (UTC)
thread_title: Synthesis and precursors

message: The imidazole sidechain of histidine has a pKa of approximately 6.0, and, overall, the amino acid has a pKa of 6.5.
What does that mean (the "overall" pKa)?  The pI of the free amino acid?  Why is that relevant?  AlphaHelical (talk) 02:14, 4 May 2013 (UTC)
thread_title:  pKa 

message: What's the molecular formula?
Eg: Phenylalanine has a chemical formula of C9H11NO2 but a molecular forumla of C6H5CH2CHCOOH
~ender 2014-10-06 5:52:AM MST — Preceding unsigned comment added by 71.223.87.212 (talk • contribs) 12:52, 6 October 2014 (UTC)
replies: text: for the condensed formula see here Jytdog (talk) 13:15, 6 October 2014 (UTC)

text: OP posted this on several amino acid pages; please see discussion here: Talk:Tryptophan#Molecular_Formula Jytdog (talk) 14:20, 6 October 2014 (UTC)
thread_title:  Molecular Formula 

message: Proteinogenic amino acid says there are 22.  I'm not clear enough to tell whether there's some subtlety, but it seems to me  that, unless someone can come up with what number 23 is, we should go with 22.--Wcoole (talk) 00:20, 27 October 2015 (UTC)
thread_title:  23 Proteinogenic amino acids? 

message: Substituted at 17:58, 29 April 2016 (UTC)
thread_title: Assessment comment

message: Hello,
In the next couple of weeks I will be editing this page. Here is my current plan outline:
I will focus on expanding the metabolism section. I will start with the Biosynthesis of Histidine and perhaps continue with the Catabolism section depending on the information I can find about Catabolism.  
More specifically I want to add information about: 
1. Histidine biosynthesis in plants 
2. How Histidine biosynthesis is regulated
3. And the Histidine precursor- L-Histidinal 
I would also like to expand the external links section by adding other interesting articles that I have found about Histidine.
 
What do you all think about this? I appreciate any feedback! 
AguayoJ (talk) 14:22, 5 May 2016 (UTC)
replies: text: Keep in mind the overall WP:WEIGHT of the sections you add in light of the article as a whole, and make sure everything you bring is reliably sourced.  We'll see on the external links.  See WP:EL for guidance. Jytdog (talk) 15:48, 5 May 2016 (UTC)
thread_title:  Outline for Editing  

message: the following was added to the article in this diff by User:Johnmichaeloliver - moved here as this is where it belongs.
[(Please note that the images of the molecular structure at the top of the panel on the right appear inconsistent.
The left one shows the imidazole side chain as CNCNC whereas the right hand version shows CCNCN)
-- Jytdog (talk) 00:02, 19 February 2017 (UTC)
thread_title:  note on structures 

message: In 1874, Miescher observed that the sperm of the Rhine salmon had “nuclein”, which the basic substance could be secured from an acid extract of the material by precipitation with chloroplatinic acid. About the new base, it contained a high proportion of nitrogen, which the ratio of the nitrogen to carbon is 5:9.
  No further investigation of the base substance was made until 1894, when Kossel isolated the protamine. He searched for a more convenient source of protamine than the Rhine salmon, which was the sperm of the sturgeon. About his method, he subjected sturine to hydrolysis with sulfuric acid, removed the reagent with barium hydroxide, and added mercuric chloride to the strongly alkaline solution. At last, he got the chloride of the protein, which had the result either with C12H20N6O4.2HCl.2H2O or with C6H9N3O3.HCl.H2O.
  On May 11 1896, Hedin can make purer base substance by removing the water and other compound based on the basis of the result of the Kossel, which can infer the right formula of the histidine between the C12H20N6O4.2HCl.2H2O and the C6H9N3O3.HCl.H2O. About his method, he added the silver nitrate to the free bases derived from the protein, and then the silver chloride was removed by the evaporation. At last, he got the purer result, C6H9N3O3, by removing the water with the silver sulfate and alcohol. 
  They both observed the histidine, but they discover the histidine in two widely separated laboratories. Of course, their materials were different, Kossel discovered histidine by using the protamine and Hedin discovered histidine by using the proteins. However, the wide distribution of histidine became apparent from the work of Kossel and his students. [7]  — Preceding unsigned comment added by Xiwentan (talk • contribs) 01:12, 8 April 2020 (UTC)
thread_title:  History of discovery: 

message: The histidine has five interaction types of histidine: (1) Cation-π interaction, (2) hydrogen-π interaction, (3) π-π stacking interaction, (4) Coordinate bond interaction and (6) Hydrogen bond interaction. About the Cation-π interaction, the protonated His+ is an organic cation, which can join the cation-π interactions as an organic cation with other aromatic amino acids (Phe, Tyr, and Trp). About hydrogen-π interaction, the polar hydrogen atom of histidine can form hydrogen-π bond with other aromatic amino acids in ‘T’ orientation. About π-π stacking interaction, the imidazole structure of histidine side chain is a conjugative π-plane, which can make π-π stacking interactions with the aromatic side chains of other amino acids (Phe, Tyr, and Trp). About Coordinate bond interaction, the basic nitrogen atom in the imidazole of histidine has a lone electron pair that make it a coordinate ligand of metallic cations, such as Zn2+ and Ca2+. About Hydrogen bond interaction, the polar hydrogen atom of the imidazole is a hydrogen-bond donor, and the basic nitrogen atom is a hydrogen-bond acceptor. [8] The bond of the histidine and water belong to the hydrogen bond interaction.  — Preceding unsigned comment added by Xiwentan (talk • contribs) 01:20, 8 April 2020 (UTC)
thread_title:  Basic interactions with other molecules 

message: https://doi.org/10.1186/s13059-018-1552-8 "Uniquely amongst animals, a complete histidine biosynthesis pathway is present in robust corals but not in complex corals or sea anemones" Copper olives (talk) 01:57, 5 October 2022 (UTC)
thread_title:  Biosynthesis in animals