Question

There are six isomeric tripeptides that contain valine, tyrosine, and glycine. Name them using both three- and one-letter abbreviations.

Short answer

The six isomeric tripeptides are VYG, VGY, YVG, YGV, GYV, GVY.

Step-by-step solution

Understanding Isomers

Isomers are compounds with the same molecular formula but different arrangements of atoms. Here, we have a combination of three amino acids: valine (V), tyrosine (Y), and glycine (G). The task is to find all possible sequences of these three amino acids.

Combinatorial Arrangements

Since the sequence of amino acids matters, each unique arrangement will result in a different isomeric tripeptide. We need to systematically arrange these amino acids to identify all possible sequences.

Listing Isomeric Tripeptides

We list all permutations of the amino acids V, Y, and G, keeping in mind that they form a tripeptide. This results in the following sequences: 1. VYG 2. VGY 3. YVG 4. YGV 5. GYV 6. GVY

Naming in Three-letter Abbreviations

The three-letter abbreviations for these isomeric tripeptides are: 1. Val-Tyr-Gly 2. Val-Gly-Tyr 3. Tyr-Val-Gly 4. Tyr-Gly-Val 5. Gly-Tyr-Val 6. Gly-Val-Tyr

Naming in One-letter Abbreviations

The one-letter abbreviations for these isomeric tripeptides are: 1. VYG 2. VGY 3. YVG 4. YGV 5. GYV 6. GVY

Key concepts

Isomeric Peptides

In biochemistry, isomeric peptides are fascinating molecules. They have the same number and types of building blocks, but these blocks are arranged differently. Think of them like a set of building bricks. You can rearrange the same bricks to build different structures. Similarly, isomeric peptides contain the same amino acids but in various sequences. The order in which amino acids are put together is crucial because it affects the peptide's properties and functions. For instance, in this exercise, we're looking at isomeric tripeptides made from valine, tyrosine, and glycine. The sequence matters, and that's why each different arrangement is a unique isomer.

Amino Acid Sequencing

Amino acid sequencing is the process of determining the order of amino acids in a peptide or protein. The sequence not only defines the peptide's structure but also its biological activity. For isomeric peptides, like the ones in the exercise, each arrangement can result in distinctly different molecules. It’s important to understand how critical sequencing is because it influences how a peptide might interact with other molecules. This is true whether looking at a short tripeptide or a long protein. Sequencing is determined using various techniques in the lab, but the core principle remains the same: the sequence dictates the function.

Valine

Valine (abbreviated as Val or V) is an essential amino acid. It cannot be synthesized by the human body, requiring us to obtain it through our diet. Valine has a branched aliphatic side chain, which makes it hydrophobic, meaning it avoids water. This characteristic means valine is often found in the core of proteins, away from the watery environment. In the context of isomeric tripeptides like VYG, VGY, and so on, valine plays a vital role in determining the peptide's overall structure. Its presence affects the conformation and, consequently, the interaction with other molecules.

Tyrosine

Tyrosine (abbreviated as Tyr or Y) is a non-essential amino acid that the body can produce from another amino acid called phenylalanine. Tyrosine has a polar side chain due to a hydroxyl group that can form hydrogen bonds. This property makes it hydrophilic, meaning it attracts water. Thus, tyrosine frequently resides on protein surfaces exposed to aqueous surroundings. In isomeric tripeptides such as YVG, YGV, and others, tyrosine's properties can infuse the peptide with the ability to participate in cell signaling pathways, given its aromatic nature and potential for phosphorylation.

Glycine

Glycine (abbreviated as Gly or G) is the smallest of the 20 standard amino acids. It has a simple structure with a single hydrogen atom as its side chain. This minimalistic structure endows glycine with great flexibility, permitting proteins to adopt a variety of shapes. Glycine is neither hydrophobic nor hydrophilic, giving it an adaptable nature. It can fit into tight spaces within a protein's structure. In the given isomeric tripeptides like GYV and GVY, glycine may allow more structural freedom, providing flexibility at points in the peptide where the sequence may need to bend or twist.