Prediction of transmembrane beta barrels?
I could tell only from my pretty poor experience.
I had all PDB entries processed with DSSP and then I've tried to find any trends in amino acid preferences. I did not find any except the pretty obvious absence of proline in double (i.e. with two neighbours) strands. Also, negative charged amino acids (I, L, V) were slightly more frequent in parallel strands. After that, I tried a sort of naive Bayes classifier for the amino acid and it's neighbours in two neighbour strands and +/-2 amino acids up/downstream. For single\double parallel\antiparallel strands, the prediction precision was about 60%.