  Predicting protein secondary structure using lattice model is one of the most
studied computational problem in bioinformatics. Here secondary structure or
three dimensional structure of protein is predicted from its amino acid
sequence. Secondary structure refers to local sub-structures of protein. Mostly
founded secondary structures are alpha helix and beta sheets. Since, it is a
problem of great potential complexity many simplified energy model have been
proposed in literature on basis of interaction of amino acid residue in
protein. Here we use well researched Hydrophobic-Polar (HP) energy model. In
this paper, we proposed hexagonal prism lattice with diagonal that can overcome
the problems of other lattice structure, e.g., parity problem. We give two
approximation algorithm for protein folding on this lattice. Our first
algorithm leads us to similar structure of helix structure which is commonly
found in protein structure. This motivated us to find next algorithm which
improves the algorithm ratio of 9/7.
