Amino Acid Hydrolysis - Video Tutorials & Practice Problems
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Amino Acid Hydrolysis
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Video transcript
In this video, we're gonna talk about our first protein cleavage technique, amino acid hydrolysis. So recall that way back in our previous lessons when we talked about peptide bonds, we said that hydrolysis is just a reaction in which bonds are cleaved with the treatment of water. And so amino acid hydrolysis is specifically when peptide bonds are cleaved with the treatment of water. And so in our example below, we're gonna look at the hydrolysis of a peptide bond. And what you'll notice is on the far left here, what we have is a dipeptide, or a peptide with just 2 amino acid residues. And these 2 amino acid residues are linked via a peptide bond, which is shown in pink right here. And so we know that if we treat our dipeptide with water, we're able to induce hydrolysis. But we also know from our previous lesson videos that hydrolysis is a very slow reaction. And so in order to speed up the reaction, we can actually add an acid catalyst that will speed up the reaction. And so H+ here is representing our acid catalyst. And so what you'll see is that our dipeptide upon hydrolysis ends up forming 2 free amino acids. 1 free amino acid here on the far left, and another free amino acid here on the right. And so complete amino acid hydrolysis can be induced with 6 molar hydrochloric acid. And 6 molar hydrochloric acid essentially is going to non specifically, it will non specifically cleave all of the peptide bonds, where all here is incredibly important and emphasized. And so, what that results in is all of the constituent amino acids of the protein, being released as free amino acids. And so down below in our example, again, what we can see is that we have a protein here on the far left, and notice that our protein has a bunch of amino acids, which are represented by these circles. And we have an amino group, a free amino group on the n terminal end of our protein and a free carboxyl group on the c terminal end of our protein. And when we treat our protein with 6 molar hydrochloric acid, we know that that is able to induce complete amino acid hydrolysis, where all of the peptide bonds are going to be cleaved with, the presence of water. So we know that most of our proteins are sitting in a solution, an aqueous solution that has water in it. And so, essentially what will happen is all the peptide bonds are going to be cleaved and that releases all of the constituent free amino acids. And so notice that they are no longer linked together via peptide bonds. Now, there is a chemical known as Ninhydrin that will actually react with these free amino acids to produce a color for quantification. And so that allows us to quantify the number, of amino acids that we have via light absorbance using a spectrophotometer. And, essentially, if we look down below, below, what you'll see is that we can treat our free amino acids over here with this chemical, that's shown that's known as Ninhydrin. And so Ninhydrin will essentially react with all of these free amino acids to produce this bluish purplish color. And that bluish purplish color can be quantified with light absorbance, using a spectrophotometer. And that allows us to quantify the number of amino acids that we have. And then, essentially, what we can do is we can take all of these free amino acids here and we can analyze them with a technique such as mass spectrometry or, HPLC in order to determine the protein composition or the amino acid composition. And so in our example down below, what you'll notice is we're treating our or we're analyzing these amino acids here with HPLC. And HPLC essentially can allow us to reveal the amino acid composition of our, protein. And so you can see that all of the amino acids have now been revealed, through, the use of HPLC. Now, what's really important actually is that once we use 6 molar hydrochloric acid, we're actually not able to determine the sequence of our protein. And so even though we are able to determine composition, which is the number types of amino acids, we have no way to determine the exact order. So remember the sequence is referring to the exact order of amino acids from the n terminal end to the c terminal end. So what that means is once we use 6 molar hydrochloric acid on a particular sample, we automatically lose the ability to determine the sequence of the residues. But, we're able to pretty easily identify the composition. And so, that's something that's important to keep in mind. So this here concludes our lesson on amino acid hydrolysis, and we'll be able to get some practice utilizing these concepts in our practice video. So I'll see you guys there.
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Problem
Problem
What is the function of ninhydrin?
A
Cleavage of proteins into free amino acids.
B
Colorimetric agent to detect amino acids.
C
Agent to carboxymethylate cysteines.
D
Serves as the mobile phase in HPLC.
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Problem
Problem
Amino acid hydrolysis via 6M HCl cleaves all the amide/peptide bonds of a protein. What do you suppose happens to the amide bonds in the R-groups of Asn & Gln residues upon treatment with 6M HCl?