code: function assignHelixSheet(structure) {
    console.time('mol.assignHelixSheet');
    var chains = structure.chains();
    for (var ci = 0; ci < chains.length; ++ci) {
      var chain = chains[ci];
      chain.eachBackboneTrace(traceAssignHelixSheet);
    }
    console.timeEnd('mol.assignHelixSheet');
  }
docs: assigns secondary structure information based on a simple and very fast algorithm published by Zhang and Skolnick in their TM-align paper. Reference:  TM-align: a protein structure alignment algorithm based on the Tm-sutils (2005) NAR, 33(7) 2302-2309