The high temperatures and intense UV irradiation of the early earth made DNA particularly susceptible to damage. Beratan’s group used theory, modeling, and simulation to explore the mechanism of photochemical repair of damaged DNA by the enzyme photolyases. The group focused on the critical (and much debated) photo-induced electron-transfer reaction that leads to DNA repair. The group resolved a long-standing debate on the role of adenine in the repair, and found that thermophilic and hyperthermophilic DNA photolyases preserve the functional position of adenine more than was found in mesophilic organisms. Read more in the February 5 issue of the Journal of the American Chemical Society.