Questions tagged [amino-acids]

This tag is for questions about amino acids, both natural and non-natural ones. It should only be applied to questions about the monomers. For peptides and proteins, use the proteins tag instead.

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8
votes
2answers
53k views

Calculating charge on amino acid from pKa

I have been given $\mathrm pK_\mathrm a$ values of an amino group, a carboxyl group and a side chain of cysteine. How can I find the ionic charge on it at different $\mathrm{pH}$ values?
32
votes
5answers
9k views

Where did amino acids get their one-letter codes?

Some amino acids have a one-letter code that's just the first letter of the name of the amino acid. This makes sense and obviously, since there is more than one amino acid that begins with the same ...
17
votes
1answer
56k views

How do I calculate the isoelectric point of amino acids, each of which has more than two values of pKa?

For most amino acids, the $\mathrm{pI}$ is simply the arithmetic mean of the amino and carboxyl $\mathrm pK_\mathrm a$s. However, for tyrosine and cysteine, which have more than one $\mathrm pK_\...
4
votes
1answer
1k views

Why are amino acids least soluble at isoelectric point?

At isoelectric point amino acids exist as zwitterions. As a molecule it is electrically neutral, but still has a positive and a negative charge. Then why are amino acids still least soluble at ...
3
votes
2answers
5k views

Why there is hydrogen bonding involved in salt bridge formation between glutamic acid and lysine?

I saw this figure on Wikipedia: After seeing this image I got really confused about the difference between these two, or maybe the similarities. Of course, I understand that a hydrogen bond can be ...
2
votes
1answer
107 views

Reaction to form amino acid

$$\ce{CH2=CH-CH=O ->[CH3SH][(1,4 addition)] Product (P_1) ->[(i) NaCN][(ii) NH3\\(iii) H3O+] Q_1}$$ Correct statement regarding $\ce{Q_1}?$ $\ce{Q_1}$ is essential amino acid $\ce{Q_1}$ is ...
4
votes
0answers
149 views

Synthesis of tripeptide using Merrifield peptide synthesis procedure - Inclusion of asparagine

I am supposed to synthesize tripeptide, $\mathrm{Ala-Asn-Phe}$, using Merrifield peptide synthesis procedure. Accordingly, I have done followings: Attached protected $\mathrm{Phe}$ as the first ...
3
votes
1answer
867 views

Comparing Polarity of Amino Acids

I know that there are polar uncharged amino acids (serine, threonine, asparagine, glutamine, cysteine) and polar charged amino acids (the basic and acidic amino acids). Does the charge on the acidic ...