Mitochondrial targeting sequences. Why 'non-amphiphilic' peptides may still be amphiphilic.

The notion that mitochondrial targeting peptides form amphiphilic alpha-helices with one apolar and one polar, positively charged face is controversial, since some experimental results seem to imply that non-amphiphilic targeting peptides can also function as import signals. However, the standard methods used to assess the amphiphilicity of a peptide may be misleading, since they do not take the flexibility of the amino acid side chains into account. To demonstrate this, we have developed a new method for calculating the amphiphilicity of helical peptides.