Large scale FMO-MP2 calculations on a massively parallel-vector computer

Graphic representation of influenza hemagglutinin (HA) antigen-antibody system, taken from the PDB dataset of 1EO8. HA is a crucial glycoprotein existing on the surface of influenza virus, and it plays a central role in antigen-antibody reactions. HA is composed of HA1 and HA2 domains (colored in green and red, respectively), while the Fab-fragment of antibody consists of two chains (yellow and purple). This target system contains total 921 residues, and the number of atoms and 6-31G basis functions are 14 086 and 78 390, respectively. The FMO-MP2 job on this target can be completed in only 53.4 min with 4096 vector-processors of the Earth Simulator. From this calculation, the important sites in molecular recognition between antigen and antibody are revealed by interaction energies.