Talk:Cysteine

message: In the field of personal care Cysteine is used for permanent wave applications predominantly in Asia.
What does "permanent wave applications" mean?  If this means to shape hair like waves, I think people would use this technique worldwide.  Could somebody clarify this?  --NormalAsylum (talk) 19:20, 19 July 2005 (UTC)
thread_title: Permanent wave applications

message: They are clearly not the same molecule. According to the systematic name, (R)-2-Amino-3-sulfanylpropionic acid the ammino group should be attached to the second carbon aton in the chain, as in the structural formula, not the first. And sulphur should not be binding two hydrogen atoms, should it? The poor second C-atom, on the other hand is a hydrogen atom short! (no sig)
No, different order, but equally screwy.  Compared to the Skeletal diagram, the sulfur branch is fine (yellow).  The violet atom has 3 hydrogens, should be NH2; the key says 'blue' is nitrogen, doesn't say what violet is.  Then the COOH, should be H-O-C=O not O=C=O   
OsamaBinLogin (talk) 00:40, 8 March 2021 (UTC)
replies: text: The skeletal formula is drawn neutral but the reality is cysteine exists as a zwitterion in most circumstances. The 3D models are based on the crystal structure of solid cysteine determined by X-ray diffraction, reported in Acta Cryst. E (2005) 61 o2739-o2742 (CSD entry LCYSTN22). It's really the skeletal formula that is misleading. The article on glycine has more details and diagrams illustrating these points. I've fixed the colour labels. --Ben (talk) 00:51, 8 March 2021 (UTC)
thread_title:  The structural formula vs the ball and stick and 3D 

message: My Biology textbook by Campbell and Reece says that Cysteine is a hydrophilic amino acid.
:What about this? 
:Ben 12:00, 1 June 2006 (UTC)
replies: text: All amino acids are soluble in water, because they are loaded with polar covalent bonds in their backbones. But that's not relevant to their behavior in proteins, where some of those polar covalent bonds have been lost in polymerization, and it's the R groups that determine classification as hydrophilic vs. hydrophobic. See 2012 section below for more on this. Jbening (talk) 22:43, 16 September 2012 (UTC)

text: See 2012 section below. Jbening (talk) 22:41, 16 September 2012 (UTC)
thread_title:  Hydrophobic vs. hydrophilic 

message: Could somebody please add the pronunciation for cysteine?
Usually pronounced, 'sis-tuh-een. Psyber93157 05:05, 10 November 2007 (UTC)
thread_title: Pronunciation

message: I'm liking the new infobox :). However, when I clicked on H in the chemical formula, it sent me to helium!  Who can fix it?  Ben 17:15, 23 March 2006 (UTC)
replies: text: It's OK, I've fixed it.  Ben 17:19, 23 March 2006 (UTC)
replies: text: Good job, Ben. -- Boris 23:28, 23 March 2006 (UTC)
thread_title:  New infobox 

message: If sheep cannot make cysteine out of methonine, which enzyme do they miss?
Cysteine is not only in grass, so when sheep eat some oher foodstuff, they are not automatically low in cysteine. When they stop eating anything at all, they die with and without wool.
I've never heard before, that sheep are missing an enzyme, what all other mammals and ruminants have, what makes methionine to cysteine. 
Cysteine and methionine are both S containing amino acids. There are such a few naturally occuring situations, that a sheep is getting enough methionine but not enough cysteine. Therefore, the sum of them both is essential and you shuld not forget to feed enough S-containing amino-acids and please do not feed just cysteine.
The whole sheep stuff in the article is not necessary, at most semi-true and should be deleted. —Preceding unsigned comment added by Jrockley (talk • contribs) 
:No, the story seems to be true, a short google survey (sheep cysteine) gives some sites which seem to support this story.  Wool is dependent on cysteine, and they need a lot of it for wool.  And they are dependent on it from their diet.  --Dirk Beetstra T C 21:16, 20 July 2006 (UTC)
thread_title:  Sheep 

message: It seems to me Cystine is a dimer of Cysteine, but the articles seem confused on this. A lot of the content is replicated, so I suggest a merge - Jack (talk) 20:34, 20 July 2006 (UTC)
thread_title:  Merge 

message: "Its use or purpose, however, is unknown, like most cigarette additives."
I don't think that's true; I think they use it for a well-known reason. Anyone know what it is? —Keenan Pepper 18:52, 27 July 2006 (UTC)
replies: text: Two thoughts: Cystine can act as an expectorant, breaking the disulfide bonds in the mucus and making it more liquid, facilitating clearing it from the lungs.  Mucus production increases in smokers. Secondly, cystine is one of the rate limiting substrates (building blocks) for glutathione (GSH), one of the most potent antioxidants in the human body.  Smoking reduces GSH. Increasing cystine would increase GSH in most folks, and this would be a benefit especially to smokers. Apparent Logic 13:49, 28 July 2006 (UTC)
replies: text: The list is of 'approved' additives, that means that they can be used, not that they are. This needs fixing as well as the removal of the speculation as to why it might be used.Muleattack (talk) 02:13, 30 June 2011 (UTC)
thread_title:  Why do they put it in cigarettes? 

message: Reference to human hair cheapest source and vague references to manufacturers in China have been repeated endlessly by internet angst sites.  Until a reliable source surfaces, I have removed all reference to "human hair" from this article.  All such stories appear to reference back to a single article in the Japanese publication ```Mainichi``` and an article about human hair in soy sauce. Norm Reitzel (talk) 20:40, 10 September 2009 (UTC)
replies: text: If a future reference is needed for this, then Jamie Olivers Food Revolution Series 2 Episode 3 details the use of human hair in the production of l-cysteine. http://www.youtube.com/watch?v=SpWvoj-IGJk  — Preceding unsigned comment added by Muleattack (talk • contribs) 01:54, 30 June 2011 (UTC)
replies: text: This reference is just a dead link. There's no reason to think the use of human hair is more than an internet rumour. Seriously, you would literally need tons of hair, which would be much cheaper from non-human sources. I've removed these references (again). Dhall27 (talk) 15:53, 5 February 2016 (UTC)
thread_title:  Human Hair Source 

message: Reads like pseudoscience to me, particularly since there are millimolar concentrations of GSH in blood already. Unless a reliable source actually describes this (nothing in PubMed and Anti-aging News is certainly NOT reliable) this does not belong in the article. Tim Vickers (talk) 22:57, 20 October 2009 (UTC)
thread_title: Insulin inactivation

message: Discussion above seems to agree that it is hydrophyllic to some extent, yet the text remains hydrophobic.  Elsewhere wikipedia lists it as polar --68.35.2.8 (talk) 13:50, 15 April 2011 (UTC)
replies: text: See 2012 section below. Jbening (talk) 22:39, 16 September 2012 (UTC)
thread_title:  polar vs hydrophobic again 

message: Could someone please explain to me why L-Cysteine is allegedly R?
Under the rules I was taught, and as listed on Cahn–Ingold–Prelog_priority_rules Wikipedia, mass only comes into it when they are the same element just different isotopes (such as Deuterium and Hydrogen). Also, double bonds are treated as 2 bonds to the same atom.
Therefore, C=OO counts as having 3 oxygen atoms and thus has a priority of 3*8 or 24. The side chain has a sulphur and 2 hydrogens, giving a priority of 2*1+16 or 18. This is still well below the 24 of the carboxyl group, and thus the carboxyl group has a higher priority, and thus the L form should still be the S form, not the R form.
The one which the L form is the R form is selenocysteine, which has selenium in the place of sulfur, giving that chain a priority of 32+2 or 34, making it higher than the carboxyl group. Unless I get a satisfactory explanation, I will change it in a week (and on the amino acid page).  — Preceding unsigned comment added by 149.171.197.22 (talk) 01:49, 16 August 2011 (UTC)
replies: text: Answered you on Talk:Amino acid. Executive summary: you're not determining the CIP precedences correctly. DMacks (talk) 01:59, 16 August 2011 (UTC)
thread_title:  Isomerism 

message: this section is confusing, how does it relate to Cysteine? Hogdotmac (talk) 23:21, 4 April 2012 (UTC)
thread_title: [[Cysteine#Cystine_crystal_morphology_and_presence_in_urine]]

message: wow whoever added the link <removed> to the subject title "precursor to glutathione" should be ashamed of themselves.  Advertising bogus pseudo-scientific product crap on wikipedia completely defeats the purpose.  Get out and don't come back.  — Preceding unsigned comment added by 130.195.203.47 (talk) 05:41, 4 July 2012 (UTC)
replies: text: I have now removed it.  I can't believe it sat there in the article for so long. In the future, you or anyone else can remove that kind of spam yourself.  -- Ed (Edgar181) 14:24, 12 December 2012 (UTC)
thread_title:  shameful advertising attempt 

message: I've just reorganized and reworded the material describing the chemical behavior of cysteine in proteins, adding more refs. While cysteine has traditionally been classed as hydrophilic, and while some of the more traditional sources do still class it as such, the actual evidence (some cited in the article) supports hydrophobicity. Add to this that the SH bond in cysteine isn't an especially polar bond by nature, and its accepted hydropathy value (given in the amino acids WP article) places it above many traditionally hydrophobic amino acids, and well above the hydrophilic amino acids. I'm certainly open to further discussion of this, but preferably if such discussion includes contrary data, rather than just citations to sources that may merely have taken the path of least resistance in keeping cysteine classed as it had been a generation ago.Jbening (talk) 20:50, 16 September 2012 (UTC)
replies: text: Excellent work, thanx.--Africangenesis (talk) 23:27, 3 October 2012 (UTC)
thread_title:  Hydrophilic vs. hydrophobic 2012 

message: The article starts out talking about "cysteine", then, without any explanation, begins talking about "L-cysteine", as if the terms were interchangeable.  For people who know about chemistry, the significance of the "L-" prefix may be quite obvious, but I, for one, would appreciate some explanation in the lede, or at the first mention of "L-cysteine".  Reading down to the "Applications" section, I learn that there is something called an "L-enantiomer", and following the link leads me to understand that cysteine molecules may appear in left-handed or right-handed form, so to speak.  This information leads me to speculate that L-cysteine may be the left-handed version, or L-enantiomer, of cysteine; but the article does not explicitly say so. Would some knowledgeable editor kindly clarify the point, as I've suggested, either in the lede or at the first mention of L-cysteine?  J. D. Crutchfield | Talk 21:05, 21 January 2016 (UTC)
thread_title:  Cysteine and L-Cysteine 

message: Substituted at 12:37, 29 April 2016 (UTC)
thread_title: Assessment comment

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thread_title:  External links modified 

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thread_title:  External links modified 

message: The part on cysteine's history is labeled as incomplete. I have found literature regarding this topic, for instance:
https://doi.org/10.1016/S0065-3233(08)60140-0
However, every literature I have come across all have combined descriptions of the history of cysteine and cystine. I also find doing so rather logical, as forcedly separating the two will inevitablely lead to an incomplete view of the subject. Thus, I recommend that we redirect the history section of cysteine into that of cystine, and I shall make additions regarding the history of both there. Pygos (talk) 07:07, 12 May 2024 (UTC)
replies: text: Support. --Smokefoot (talk) 13:07, 12 May 2024 (UTC)
thread_title:  History of cysteine and cystine 

message: Where in the given reference is it specified that cysteine is "semiessential"? Reading it as a lay person I don't understand. Is this fact in the given reference? Danuthaiduc (talk) 20:56, 12 May 2024 (UTC)
thread_title:  Semiessential