Hydrogen bonding cooperativity of water to nucleotide recognition: Structure of octadecahydrated inosine 5′-monophosphate, 2(C₁₀H₁₂N₄O₈P)·18H ₂O at atomic resolution

The crystal structure of an octadecahydrated complex between two inosine 5′-monophosphate (IMP) has been determined at atomic resolution, which reveals the hydrogen bonding and the coordination cooperativity of water molecules to nucleotide recognition. The crystal belongs to monoclinic space group P2₁ with cell dimensions a = 8.65(1), b = 21.90(1), c = 12.37(1)Å, and β = 110.38(9)°. The ribose hydroxyls, purine N7, keto(O6) bonded water molecules W1, W2, W5, W6, W8 and the phosphate bridge forming water oxygens of W4, W7, W11 appear to play an invariant role in their hydrogen bonding interactions with the IMPs. The synergistic role of the water molecules W5, W6, W8 in the purine staking domain (N27⋯W5 = 2.583, N17⋯W5 = 2.563, O16⋯W8 = 2.759, O26⋯W6 = 2.723 Å) have been clearly observed for the first time. The complexation of the water molecules through variable hydrogen bonding coordination indicate their functional involvement through extensive cooperative donoracceptor network mechanism. The occurrence of hydrogen-bonded water spines, water bridges and their interplay in the structural association of IMPs could indicate the possible viability of those aquatic centers in the biological situation.