Mg spin affects adenosinetriphosphate activity

The Schlegel-Frisch ab initio molecular dynamics (ADMP) (DFT:B3LYP), T = 310 K, is used to study complexation between adenosinetriphosphate (ATP), ATP subsystem, and magnesium cofactor [Mg(H2O)6]2+, Mg subsystem, in a water pool, modeled with 78 water molecules, in singlet (S) and triplet (T) states. The computations prove that the way of ATP cleavage is governed by the electron spin of Mg. In the S state Mg prefers chelation of γ-β-phosphate oxygens (O1-O2), whereas in the T state it chelates β-α-phosphate oxygens (O2-O3) or produces a single-bonded intermediate. Unlike the chelates, which initiate ionic reaction paths, the single-bonded intermediate starts off a free-radical path of ATP cleavage, yielding a highly reactive adenosinemonophosphate ion-radical, AMP-, earlier observed in the CIDNP (Chemically Induced Dynamic Nuclear Polarization) experiment (A.A. Tulub, 2006). The free-radical path is highly sensitive to Mg nuclear spin, which through a hyperfine interaction favors the production of unpaired electron spins. The unique role of Mg in ATP cleavage comes through its ability to serve as a unique redox center, initially accepting an electron from ATP and then giving it back to products. Redox activity of Mg differs for T and S states and affects the number of coordinated water molecules. The findings give a new insight into the NTP (N = nucleoside) energetics and assembly of NTP-operating molecules, including proteins. PACS codes: 87.15.-v