In general, protein molecules that are neutral in surface charge or have hydrophobic surfaces are prone to interact with each other and hence cause changes in stability. This propensity is highly dependent on the primary amino acid sequence as well as which types of amino acids are dominant in the protein. If there are more hydrophilic and charged amino acids on the surface of the proteins, they will be less susceptible to aggregation caused by surface interactions. On the other hand, if the proteins are folded in such a way that a lot of the hydrophobic amino acids are exposed on the surface, they will be more susceptible to changes in stability. As a result, proteins that have mutations in their primary sequence are likely to suffer from stability issues. In specific applications, however, site-specific mutations are designed on purpose to enhance the stability or activity of a protein.
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