A segment of a protein forms a single regular right-handed α-helix with 54 residues…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A segment of a protein forms a single regular right-handed α-helix with 54 residues. Use 3.6 residues per turn and a rise of per residue. The C=O of residue bonds to the N-H of residue . Find the number of turns, the length of the segment and the number of hydrogen bonds in the helix.
Need a reminder? The key ideaShow
A peptide bond forms with the loss of one water. A chain of residues has bonds, and its molar mass is the sum of the free amino acids minus for each bond. In an α-helix there are 3.6 residues per turn and a rise of 0.15 nm per residue. The C=O of residue bonds to the N-H of residue . The number of sequences with repeats is divided by the factorial of each repeat.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Use the three numbers of the helix.
Step 1. Turns. .
Step 2. Length. .
Step 3. Hydrogen bonds. Residues 1 to 50 each bond to a residue four places ahead. Residues 51 to 54 have none ahead. So bonds.
Answer: 15 turns, and 50 hydrogen bonds.
Check. The pitch is turns in , which is per turn, as expected.
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