**Local structure prediction by combining evolutionary and structural information.**
Amino acid frequencies are estimated using two different methods: (1). from multiple sequence alignment (evolutionary frequencies)
and (2). from local structure propensities derived by statistical analysis of a set of protein structures (structure frequencies).
An optimal linear combination of these two types of frequencies:

*F*(combined) = *w · F*(evolutionary) + (1-*w*) · *F*(structure)

can give better local
structure prediction accuracies than using either frequencies alone, as reflected by the Q3 and SOV scores of secondary structure prediction.
In this diagram, when weight (*w*) is zero, only structural frequencies are used. when weight is 1, only evolutionary frequencies are used. The optimal weight
is about 0.6.