The prediction of intermolecular proton-transfer of guanine-cytosine base pair under the influence of fragments from decomposed MOFs.

Metal-organic frameworks (MOFs) can be decomposed into various fragments, including negative/positive charges, Zn+ or Cu2+ when used as drug delivery materials. To evaluate the safety of MOFs, different mechanisms of intermolecular proton-transfer in guanine-cytosine (GC) base pair under the influence of such fragments were investigated by density functional theory methods. In a vacuum, calculation results show that an excess electron assists proton transfer in the anionic GC radical, and a hole assists proton transfer in the cationic GC radical with small energy barriers. The mechanism for Zn+-GC transfer is that the located hole assists proton transfer from G to C. All proton-transfers of Cu2+-GC become spontaneous with stable proton-transferred structures, and the driving force is the Cu2+ due to its electrostatic and oxidative effects. However, in a micro-water environment, the average energy barrier of all proton-transfer processes increases by 2.8 kcal mol-1 because of the redistribution of charges. Water molecules play a very important role in buffering, and the influence of fragments on intermolecular proton-transfer processes of GC is reduced.