Protein Structural Elements and Folding

The protein design and folding problems are still two of the unresolved problems of our times. A solution to the protein folding problem is the determination of the possible pathways of folding of a well constructed sequence of amino acids. The protein design problem on the other hand is the selection of a well formed amino acid sequence from the range of possible sequences. The number of possible sequences goes up as the number of distinct amino acids (i.e. 20) to the power of the length of the peptide chain. So a protein of length 57 such as basic pancreatic trypsin inhibitor is one protein out of 2057 possible proteins. Our understanding of how to select one workable foldable protein out of this huge number is very rudimentary.