Quantum Computer Simulation of Protein Protonation

In attempts to simulate the protonation of proteins,a major challengeis that the number of protonation states grows rapidly as a function(2( N )) of the number of protonation sites(N). Expression on the free energy of the protonationstate as an N-site Ising model  using anempirical Generalized-Born model  allows a quantum computerto efficiently determine the important states at a given pH valueand subsequently reconstruct the pH titration process at all sites.Compared with the exact results painstakingly obtained with classicalcomputers, the results obtained using quantum computers show goodagreement for staphylococcal nuclease and excellent agreement for & alpha;-lactalbumin. This work illustrates the effectiveness of quantumcomputers in sampling important physical states, which may be usefulin attacking challenging biomolecular problems.