An all-electron calculation on the non-symmetric insulin hexamer was successfully carried out using a precise initial guess of the combined quasi-canonical localized orbitals and the parallel density functional program employing the distributed matrices. The numbers of residues, atoms, and orbitals were 306, 4728, and 26 790, respectively. To our knowledge, insulin hexamer is the largest system calculated using the full-scale canonical density functional molecular orbital method. The calculation for the initial guess and the insulin hexamer took 26.5 It using 24 Xeon processors (3.2 GHz) and 65 h using 64 Itanium 2 processors (1.3 GHz), respectively. (c) 2006 Elsevier B.V. All rights reserved.