Problem:
A study looked at mutations in the hydrophobic core of a protein of interest. The Tm for the wild-type protein (no mutations) was compared with that of a few site-directed mutants. The data is shown below:
Wild-type 53.5 oC
L46A 43 oC
L118A 40 oC
L99A 36 oC
Question: Why do all of these mutants substitute alanine for the naturally-occurring amino acid?
Explain your reasoning.