Final answer:
NMR spectroscopy allows you to determine if a protein contains an alpha helix.
Step-by-step explanation:
The method that allows you to determine if a protein contains an alpha helix is NMR spectroscopy.
NMR spectroscopy works by using the magnetic properties of atoms to determine the three-dimensional structure of proteins in aqueous solution. It can provide detailed information about the secondary structure of a protein, including the presence of alpha helices.