Article (edit | visual edit | history) · Article talk (edit | history) · Watch • Watch article reassessment page • Most recent review

Result: Kept; issues resolved. ~~ AirshipJungleman29 (talk) 18:36, 6 March 2023 (UTC)[reply]

 Because of an overload of chemistry articles at GAR, if delisting, do not close before 1 March.

Looks like there's some amounts of uncited material including

• "an acid is a species that can donate a proton to another species, and a base is one that can accept a proton. This criterion is used to label the groups in the above illustration. Notice that aspartate and glutamate are the principal groups that act as Brønsted bases, and the common references to these as acidic amino acids (together with the C terminal) is completely wrong and misleading. Likewise the so-called basic amino acids include one (histidine) that acts as both a Brønsted acid and a base, one (lysine) that acts primarily as a Brønsted acid, and one (arginine) that is normally irrelevant to acid-base behavior as it has a fixed positive charge. In addition, tyrosine and cysteine, which act primarily as acids at neutral pH, are usually forgotten in the usual classification." From Zwitterion.
• "This pH is known as the isoelectric point pI. For amino acids with charged side chains, the pKa of the side chain is involved. Thus for aspartate or glutamate with negative side chains, the terminal amino group is essentially entirely in the charged form NH, but this positive charge needs to be balanced by the state with just one C-terminal carboxylate group is negatively charged. This occurs halfway between the two carboxylate pKa values: Similar considerations apply to other amino acids with ionizable side-chains, including not only glutamate (similar to aspartate), but also cysteine, histidine, lysine, tyrosine and arginine with positive side chains. Amino acids have zero mobility in electrophoresis at their isoelectric point, although this behaviour is more usually exploited for peptides and proteins than single amino acids. Zwitterions have minimum solubility at their isoelectric point, and some amino acids (in particular, with nonpolar side chains) can be isolated by precipitation from water by adjusting the pH to the required isoelectric point." From Isoelectric point
• "D-amino acid residues are found in some proteins, but they are rare." from Istoterism
• and "The obsolete term remains frequent." from general structure.

Most of side chains looks uncited but I think citation 6 is supposed to be one large general reference. Though I'm not sure. Either way, the things above will need to be cited. Onegreatjoke (talk) 22:15, 8 February 2023 (UTC)[reply]

Also this may just be me but the history section seems really small for something as important as amino acids. Onegreatjoke (talk) 22:19, 8 February 2023 (UTC)[reply]

I've attempted to address some of the points raised here:

• I've reworded this paragraph to remove the confusing references to aspartate/glutamate as acidic, and protonated Lys/Arg as basic. Instead, I put the focus on their typical acid/base nature at physiological pH. The way this paragraph was previously written seemed to me that it was coming from someone who has had to correct a lot of undergraduate students on their misconceptions of acid/base chemistry or who were getting tripped up by their conjugate acid/base states. I also included a textbook reference from the one I had lying around, since no one should have to dig for an article from the 1920s unless they're into that.
• included a reference to the relevant pages in that same textbook for amino acid pI's
• pulled a reference from the D-amino acid article and placed it here with an added explanation.
• someone else removed the reference to the obsolete term.

Regarding the side chains section; citation 6 does not cover any of the claims there, and would require time to sort those out. The history section, while short, does seem to cover the main points of early amino acid well. Though I am no expert there. ― Synpath 22:16, 18 February 2023 (UTC)[reply]

I have rewritten the side chains section leaning heavily on a textbook for reference. I invite anyone interested to read it over and make changes, as I'm sure what I've written can be made better. ― Synpath 23:34, 26 February 2023 (UTC)[reply]

I've done a little tidying and wikilinking throughout the article. Chiswick Chap (talk) 15:47, 3 March 2023 (UTC)[reply]