Mg spin affects adenosinetriphosphate activity

Abstract

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(H 2 O) 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 --phosphate oxygens (O1-O2), whereas in the T state it chelates --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.

Spin effects govern DNA/RNA nucleotide polymerization

“…The decomposition in the water environment spans over 5.4 ps and practically does not affect the geometry of AMP (we stress here again that this time interval is the pure ATP decomposition, when the chelate with the Mg is formed; the total CPMD run interval is much longer, 10 -6 s, see section 2, and includes the separation of the produced fragments, their repulsion, approach, diffusion etc. (Figure 3(a)), one of the decomposition products, reaction (1) [15] thus producing the O -radical. The electron transfer is coupled with the proton transfer from the Zundel cation onto the O -, Figures 3(a), (b) (structure-1, 2, Table 1).…”

“…It is initiated by altering spin symmetry of the Mg 2+ upon its excitation from the lowest in energy S state into the lowest in energy triplet (T) state. The mechanism was recently revealed in quantum computer experiments [15,16] and indirectly proved by the Chemically Induced P nuclei [15]. The excitation into the T state that proceeds in vitro in a femtosecond interval results in producing the two ion-radicals, Mg + and NТP 3-(the dot stands for a radical), with the latter showing a rapid decomposition into the NМP -.…”

“…] SS (SS stands for a spin-separated state with one electron on the Mg and the rest on the NTP) is, on the contrary, highly rapid, 5 ps [15,16]. At this very point one must make it clear that the 5 ps interval assumes the pure decomposition time when the Mg cation is just chelated by the O2-O3 fragment of the ATP and the chelate is energetically unstable (the difference in the total energy for the separated ATP+ (water shell) molecule and the (H 2 O) 6 Mg 2+ and their chelate is around 20 kcal/mol) that allows it to show such a fast decomposition.…”

“…Besides the ionic mechanism of NTP cleavage there is an alternative one-the radical mechanism [15]. It is initiated by altering spin symmetry of the Mg 2+ upon its excitation from the lowest in energy S state into the lowest in energy triplet (T) state.…”

“…The excitation into the T state that proceeds in vitro in a femtosecond interval results in producing the two ion-radicals, Mg + and NТP 3-(the dot stands for a radical), with the latter showing a rapid decomposition into the NМP -. Totally, the process spans over the 1.25  10 2 picosecond interval, reaction (1), if the latter thought in the water bulk of 78 water molecules (the corresponding water box is 12.17  8.17  21.18 Å 3 that includes the ATP molecule (N = Ade) with the first-second water shell around it and the (H 2 O) 6 Mg 2+ initially distanced from the O2-ATP by 8 Å; water molecules imitate the real solution, for details see [15]):…”