Talk:Ellman's reagent

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Molecular Biology: MCB

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mistake with the image

There is a mistake with the product. This is R-S and not H-S... —Preceding unsigned comment added by 139.165.84.48 (talk) 09:14, 20 May 2010 (UTC)[reply]

Fixed. Tim Vickers (talk) 16:15, 20 May 2010 (UTC)[reply]

I have to ask whether this has been fixed properly, because I still see an imbalance in the reaction scheme (I think the first product should be R-S-S-(nitrobenzolate) instead of H-S-S-(nitrobenzolate)). —Preceding unsigned comment added by 192.38.103.3 (talk) 13:32, 25 June 2010 (UTC)[reply]

Fixed. I have now replaced the image with a corrected version. -- Ed (Edgar181) 00:48, 13 December 2010 (UTC)[reply]

Improper non-units expression

The very ideas such as "molarity" and "molality" and "normality" and the like are confusing enough and easily avoided by simply using standard units of measurement to express the concentration.

Compounding the problem with some confusing notion of molarity divided by centimeters is something that has no place in an encyclopedia article, especially in an isolated not-otherwise-explained units. Furthermore, standards organizations are now deprecating the use of "molarity" and the like, details to follow.

In any case, the "mM cm⁻¹ is never correct—not with that UPRIGHT M. Gene Nygaard 03:58, 20 October 2007 (UTC)[reply]

Jargon usage in some field isn't particularly relevant in determining what we should use in a general audience encyclopedia. Most anybody with any technical knowledge knows what a [[mole (unit)|] is. Few of them know what molarity is, and hardly anybody is going to grasp molarity divided by length without difficulty. Gene Nygaard 04:00, 20 October 2007 (UTC)[reply]

What units would you suggest that would allow us to express an absorbance coefficient without a unit of length? Tim Vickers 04:09, 20 October 2007 (UTC)[reply]

It isn't the presence of the unit of length I complained about. It is the concatenation of that with a hard-to-connect up notion of molarity.

The fact that the use of "molarity" is non-standard and now deprecated is not "my notion". Here is the national standards laboratory of the United States, NIST, in their Guide for the Use of the International System of Units (SI), 1995, NIST Special Publication 811, Chapter 8 Comments on Some Quantities and Their Units, section 8.6.5 Concentration of B; amount-of-substance concentration of B:[1]

The term molarity and the symbol M should no longer be used because they, too, are obsolete.

Someone needs to at the very least go though and read and consider NIST's arguments on these points, and then come back and reword what is here so that it is understandable at the very least by technically literate people outside the specialized field in which it is used. If you aren't familiar with the conventions NIST uses, that will look a little strange at first, too. But to me the simplest, most salient fact is that all of these various concentration measures are more easily understood by most everybody by just using standard SI units of measure, and expressing the concentrations as mol/mol, mol/kg, mol/L, and the like. Then you don't need to know any specialized jargon; you just need to know the units of measure. The interdisciplinary nature of the SI is just as important or even more so than its international nature. Gene Nygaard 04:22, 20 October 2007 (UTC)[reply]

And, to boil my point down to its simplest terms:

Anybody who understands molarity will necessarily be able to understand mol/L (or mol L⁻¹ as long as they are otherwise familiar with that notation).

The converse is not true. Gene Nygaard 04:29, 20 October 2007 (UTC)[reply]

As noted on the Wikipedia page about molarity, while this usage might have been recommended by this particular standards agency, it is not used in the field. Have a look at the current style guide of the Journal of Biological Chemistry for example - (link) or the IUBMB recommendations for biochemical thermodynamics - (Link). Your enthusiasm for this novel nomenclature is admirable, but Wikipedia follows rather than leads in these matters. Tim Vickers 15:11, 20 October 2007 (UTC)[reply]

Also look at the literature, I searched for "extinction coefficient" in PubMed and scanned the most recent abstracts:

Silverman LN, Pitzer ME, Ankomah PO, Boxer SG, Fenlon EE (2007). "Vibrational stark effect probes for nucleic acids". The journal of physical chemistry. B. 111 (40): 11611–3. doi:10.1021/jp0750912. PMID 17877390.{{cite journal}}: CS1 maint: multiple names: authors list (link)

Lee C, Yum JH, Choi H; et al. (2007). "Phenomenally High Molar Extinction Coefficient Sensitizer with "Donor-Acceptor" Ligands for Dye Sensitized Solar Cell Applications". doi:10.1021/ic700996x. PMID 17824603. {{cite journal}}: Cite journal requires |journal= (help); Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)

Kebabian PL, Robinson WA, Freedman A (2007). "Optical extinction monitor using cw cavity enhanced detection". The Review of scientific instruments. 78 (6): 063102. doi:10.1063/1.2744223. PMID 17614600.{{cite journal}}: CS1 maint: multiple names: authors list (link)

Kuipers BJ, Gruppen H (2007). "Prediction of molar extinction coefficients of proteins and peptides using UV absorption of the constituent amino acids at 214 nm to enable quantitative reverse phase high-performance liquid chromatography-mass spectrometry analysis". J. Agric. Food Chem. 55 (14): 5445–51. doi:10.1021/jf070337l. PMID 17539659.

Since there have been no further comments, I have reverted to the usual nomenclature. Tim Vickers 21:10, 23 October 2007 (UTC)[reply]

I second TimVickers usage. Just because NIST issues a guideline doesn't mean that we need to deviate from common usage (after all, NIST is only relevant to the USA). I'm a chemical engineer, and if need be, I can produce reams of current references that use M to mean mols/L. Cheers, --Bfigura ^(talk) 20:44, 25 October 2007 (UTC)[reply]

Reaction Scheme

The scheme pictured in this page is showing the nitro (NO2) group meta to the sulfur atoms, and the carboxylic group para. The two groups should be switched - Nexxen (talk) 08:52, 15 November 2009 (UTC)[reply]

Thank you, corrected. Tim Vickers (talk) 18:31, 15 November 2009 (UTC)[reply]

Not been completly corrected, the reaction scheme on the page is correct, however if you click the image in the article two of the substituents switch (as described above), and then if you click on the image they switch again. The link is http://en.wikipedia.org/wiki/File:DTNB_reaction.png. TB. —Preceding unsigned comment added by Audiolessonover (talk • contribs) 16:29, 11 May 2010 (UTC)[reply]

"Technical"

I removed the tag. It is silly to expect an article about a specialized reagent to be non-technical. --Rifleman 82 (talk) 02:40, 4 October 2010 (UTC)[reply]

That is just fine with me. Thanks for the note. Hey, maybe you want to have a look at Category:Wikipedia articles that are too technical? Drmies (talk) 02:55, 4 October 2010 (UTC)[reply]

Ionization of byproduct

"to give 2-nitro-5-thiobenzoate (NTB^-), which ionizes to the NTB^2- dianion in water at neutral and alkaline pH." But the reaction scheme has fully protonated NTB as the product (balanced reaction from protonated thiol). Sounds like neutral NTB, even if it is technically formed, immediately would ionize (twice), so maybe a second scheme with that process would be simplest solution? Need to have the description match the equation. And especially important to have the structure of the NTB^2- form, since that's the key to the reagent's notability. The intermediate (monoanion) structure would also be useful to "chemists who aren't familiar with this particular chemical" identify which site (thiol vs carboxyl) is the more acidic one. DMacks (talk) 03:43, 4 October 2010 (UTC)[reply]

Merge from Ellman's assay

Are these 2 articles not about the same process ? Expert needed . --Triwbe (talk) 08:04, 16 November 2010 (UTC)[reply]

Concur. One could write speciifcally about the test-reagent as a chemical, and specifically about the test protocol, but the two are inter-related and at least at this time doesn't seem like sufficient material to make either of those substantially long pages. May as well unify and discuss together (the chemistry is interesting and the chemical is notable because of the assay, the assay works because of the chemical, etc.). The assay page is kinda fluffy beyond the chemistry description anyway (especially the "Thiol Chemistry" section sounds like a vague school-essay capsule?). DMacks (talk) 13:49, 16 November 2010 (UTC)[reply]