A Simple Parameter Relating Sequences with Folding Rates of Small α Helical Proteins

It is found that the helix parameter (HP), which favors clustering of non-polar residues, is linearly correlated with the logarithms of rate constants of folding of small two-state α-helical proteins. The definition is HP = NH-1 Σ [fi+ (fi-1+fi+1) / 2], where fi=1 or -1, if the i'th residue is hydrophobic or hydrophilic, respectively, NH is the number of hydrophobic residues and the summation is taken over the hydrophobic residues.