The partial double bond character of a peptide bond has its greatest effect on which of the following levels of structure?

Secondary structure of protein.

Explanation:

The protein undergoes the different processes to fold properly and functionally active. Different stages of the protein folding are primary structure, secondary structure, tertiary structure and Quaternary structure of the protein.

The partial double bond character is present in the backbone of the peptides. These bonds result in the different dihedral angle and the angle can be observed during the secondary structure of the protein. Depending on the bond character the peptide may undergo the alpha helix or the beta pleat sheet structure of the protein.

Thus, the answer is secondary structure of protein.