
Peptide Stability in Helices and Strands
Hard
Why does nature fold proteins into helices and strands instead of stretching them out flat? The answer involves energy. Folded shapes pack atoms closer together, creating stronger attractions.
You use computer software to build model peptides (short protein chains) from repeating amino acid blocks. Each peptide is modeled in three shapes:
- extended
- strand
- helix Then you compare their potential energies.
Helices turn out to be the most stable shape. Strands come second. Extended conformations are the least stable. The gap in stability grows as more amino acid blocks are added. Van der Waals forces (weak attractions between nearby atoms) contribute the most to this difference.
Hypothesis
The hypothesis is that nature prefers strands and helices in building biomolecules.
Method & Materials
You will use a computer to make model peptides with repeating pentapeptide blocks of the type of [AAAAA](n) and [DAAAK](n). You will model extended, strand, and helical structures and measure and compare the stabilities of the peptides with and without energy minimization.
You will need a computer, the programs Insight II, IsisDraw, and DeepView.
Results
The results showed that helix is in general the most stable conformation, followed by strand, whereas the least stable is the extended conformation. The van der Waals term contributed the most to the increase in stability and to a lesser extend the electrostatic term.
Why do this project?
This science project is interesting because it shows how nature prefers strands and helices when building biomolecules.
Also Consider
Experiment variations to consider include testing different types of peptides and varying the number of amino acid blocks.
Full project details
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