All Questions
6
questions
0
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1
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How do I calculate the ensemble-average net charge of an amino acid at given pH?
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that ...
- 51
3
votes
1
answer
303
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Dissociation constants of leucine
Leucine is a type of amino acid. Let me write its chemical formula as $\ce{NH2-C5H10-COOH}$. On the wikipedia page, https://en.wikipedia.org/wiki/Leucine, there are two dissociation constants, one for ...
- 506
1
vote
2
answers
4k
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Applying Henderson–Hasselbalch equation to amino acids: which pKa to use to calculate Z-/HZ ratio?
I was wondering which $\mathrm{p}K_\mathrm{a}$ to use when calculating the ratio of $\ce{HZ}$ to $\ce{Z-}$ of amino acids, the Henderson–Hasselbalch formula used:
$$\mathrm{pH} = \mathrm{p}K_\text{a} ...
- 419
-5
votes
2
answers
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Where on the backbone does a peptide get protonated at low pH?
As a particular example, how does the backbone of a peptide look at $\mathrm{pH}~2$? Where does the backbone get protonated in such an acidic solution?
I know that at low $\mathrm{pH}$ the free ...
- 197
9
votes
2
answers
9k
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Why isn't the side chain of arginine totally protonated at low pH?
I was wondering why arginine cannot be protonated at $\mathrm{pH\ 0}$ on all the $\ce{N}$ atoms in the side chain, as they all have a free electron pair. As this image shows, it can only be protonated ...
- 419
19
votes
1
answer
66k
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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_\...
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