Consider the following tripeptide:
b. Give the one-letter and three-letter abbreviations of this tripeptide.

Question

Consider the following tripeptide:

b. Give the one-letter and three-letter abbreviations of this tripeptide.

Accepted Answer

Alright, hello everyone. So this question is asking us to provide the one letter and three letter abbreviations for the peptide shown below. So as we can see here, we have a tripeptide, which means that we have three different amino acids to identify. Now by convention, amino acids are or specifically peptides are drawn and named from N to C. So from the N terminus to the C terminus going from left to right, we can see this in the structure too because notice how the amino group or the free amino group I should say is to the left of the structure and the free carboxyl group is to the right. And so for each amino acid between the amino nitrogen and the carbon carbon, we have the alpha carbon, which is the center of each amino acid and has the side chain that identifies each amino acid. So now based on the side chains, let's go ahead and identify our amino acids starting off with the one that's farthest to the left, we can see that branching off of the alpha carbon is one additional carbon and a file or s group. This if you recall is characteristic of cystine or cys. Now, the majority of three letter abbreviations tend to just be the first three letters of the amino acids name. The exceptions are asparagine, glutamine, tryptophan, and isol lucine, but most others or the remaining other amino acids are just based on the first three letters of their name. So cysteine is simply going to be cys moving on. Now to the next amino acid branching off of the alpha carbon, we have a total of a three carbon chain with a methyl substituent branching off of the first carbon directly attached to the alpha carbon. And so based on this, this is going to be isoleucine or ile isol lucine if you recall is one of the exceptions to our three letter abbreviation rule. And last but not least we have one more side chain that is an isopropyl group. It's a two carbon chain with a methyl substituent branching off of the first carbon. And that if you recall is characteristic of veiling or VA L I like to think about the side chain of valine as looking like the letter V. So that helps me match the side chain to the amino acid. So now for the three letter abbreviations, we have cys for cysteine ile for isoleucine and va for valle. So now let's talk about the one letter abbreviations. Now sometimes one letter abbreviations are intuitive and sometimes they're not. And unlike three letter abbreviations that are separated by a dash in between them. The one letter abbreviations are not separated, rather it's going to look like an acronym. So as I said before, sometimes one letter abbreviations are intuitive and sometimes they're not, for example, if we take the amino acid phenylalanine, the three letter abbreviation is phe but the one letter code is F. So it really depends on the amino acid. The good news is that for cysteine Isoleucine and Valine, their three letter abbreviations are simply the first letters of their names. So for Cystine, it's C for is sousing its I and for veiling its V. But again, this is not true for all amino acids. So just keep that in mind in any case though, here you have it. Now we have our completed final answer. And so with that being said, thank you so very much for watching and I hope you found this helpful.

Consider the following tripeptide:

b. Give the one-letter and three-letter abbreviations of this tripeptide.

Verified video answer for a similar problem:

Key Concepts

Amino Acids

Peptide Bonds

Abbreviations of Amino Acids