Identify the amino acids present in the peptide shown and name the peptide using the three-letter abbreviations.

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Welcome back everybody. Our next problem says, consider the following peptide. We have a really enormous structure here that we'll walk our way through in a few minutes. And we have two goals for this. Number one, determine the amino acids present in the peptide. And number two use three letter abbreviations to name the peptide. So when looking at a giant structure like this and wanting to identify the amino acids, we'll want to focus on the backbone of each amino acid. So that would be H two N. Again, by convention, we start with the N terminal bonded to an alpha carbon which has a hydrogen and an R group which has a bond too, a carbon carbon and then that's a carboxylic acid. So it also has an oh, that's the amino acid by itself. However, in the case of a polypeptide like this, we need to look at the form in which we have peptide bonds between them. So two of these react together and our polypeptide chain will look like H two N or alpha carbon with an R group carbon carbon with a double bond to an oxygen. And then that will be directly bonded to the nitrogen of the next peptide or the next amino acid, excuse me. So I'm going to highlight in blue that peptide bond that is formed. A molecule of water is eliminated. The oh group from the carboxylic acid is eliminated along with a hydrogen from the next amino acids. I mean group at the end forming that peptide bond. So then we have N H and then we go into the alpha carbon of the next amino acid. So we'll put R prime to show it's a different amino acid with a different R group and then that would have its carbon carbon next. And if this is the last one in the chain, then a carboxylic acid. So we have our N terminal to our c terminal showing how the peptide bond links the two. So if we keep that backbone in mind, we can pick out the peptide bonds each amino acid and then look for the R groups to name them since the R groups are what distinguishes one amino acid from another. So we'll start on the left side again, conventional to start with the N terminal. And when we name a peptide, we start with the N terminal. So let's hunt around on our left side for an H two N group or an H three N plus can be written in the charge form as well. In this case, we have no charges on our structure. So we'll start with his H two N that's on the left. Keep in mind, some of our amino acids have amine groups in them. So make sure you're actually in the backbone of your first amino acid and not stuck off on a side chain. But in this case, we have our H two N and then we have a carbon, then we have a carbon carbon and another nitrogen. Well, this one's a little tricky. It certainly looks like the backbone of an amino acid, but there's nothing on the alpha carbon. However, let's recall that we have the amino acid, Glycine and glycine has just a hydrogen atom as it's our group. So this alpha carbon put a little blue dot There has two hydran on it. So we can name that Gyne if we say that that our group is just a hydrogen. So that's a little bit trick, definitely a bit tricky to start out with since we're left wondering, wait, what's going on, what is this? Always remember that you've got glycine with just a hydrogen. So in that case, we can identify our peptide bond and I'm going to highlight it in blue as I did on my structure between the carbon carbon and the nitrogen of the next amino acid. And again, that our group, a circle in red is just the hydrogen that is implied on that alpha carbon. So, Gly glycine is our first amino acid going to write down below. Write it out as in that format with the abbreviations where you put a hyphen in between each abbreviation that hyphen representing the peptide bond between them. So let's move on to our next amino acid. There's the nitrogen, here's my alpha carbon. And so this isopropyl group attached to the alpha carbon is my R group. Well, the amino acid that has an isopropyl group as its R group is vine, which is VA L. So we'll add that to our growing chain there with a hyphen after it. So let's once again, look at the peptide bond. So we've got the alpha carbon with its isopropyl group, carbon carbon with a double bond to an O and then that bond to a nitrogen that is our peptide bond. So now we're on to amino acid number three, check that we're going along. It seems to be written with just our backbone going along here in the middle, but always double check that we're not changing up the structure at the last minute and going off into a side chain. So from the nitrogen, we have a carbon with a branch on it, a carbon carbon and then another nitrogen. So this is the backbone continuing. And therefore, our group is this chain coming off, we have ach two and then a benzene ring and then an oh. So I've been all attached to ach two. So the amino acid that has that R group is terrace or tyra, which is abbreviated Tyr So we'll put that as our next amino acid Tyr with a hyphen. There. Let's go along and find our peptide bond which again highlight in blue between the carbon carbon and the next nitrogen and hunt for our next R group. U go along from nitrogen to alpha carbon. We see that's carbon carbon on the other side. So we can identify our chain. In this case, we have CH two, ch two and then an amid group. So the second CH two is bonded to a Carbone group. So C double bodo and then an NH two. So that side chain there is glutamine which is abbreviated GLN know that you need to be careful not to mix that up with GLU which is glutamic acid. So don't mix those two up. So in this case, we need GLN for glutamine, add that onto our growing chain, bind the peptide bond to the next amino acid. So we have our glutamine side chain, then carbonyl carbon peptide bond highlighted in blue to the next nitrogen. Now we're on to our next amino acid. So after the nitrogen, we have our alpha carbon, it has a chain of 1234 CH, two groups and then terminating in an NH two group. So there's four CH two s with an NH two are the amino acid lysine which is abbreviated LYS. So I add that to my chain. Let's look for our next peptide bond. So I've got my alpha carbon carbon carbon peptide bond to a nitrogen. And I'm on to my last amino acid. Now, the c terminal amino acid and in this case, I have a side chain and so I have nitrogen alpha carbon. My side chain is a very long one. I've got CH two ch two ch two. So three carbons last one bonded to an NH that nitrogen is bonded to another carbon, which has a single bond to an NH two group and a double bond to an NH group. So that's my long R group and that corresponds to amino acid arginine or A RG. So add that as our c terminal. So we have determined the amino acids present and we've used three letter abbreviations to name the peptide. We have gly hyphen va L hyphen Tyr hyphen gln hyphen lys hyphen A RG. See you in the next video.

Identify the amino acids present in the peptide shown and name the peptide using the three-letter abbreviations.

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Key Concepts

Amino Acids

Peptide Structure

Three-Letter Abbreviations