The Hydrogen Bond Fitting Functions Of Eight Types Of Hydrogen Bonds In ABEEMσπ/MM Model

Hydrogen bonds play an important role in the life processes. The life system is anaqueous system. So it is very necessary to study the hydrogen bonds between biologicalmolecules and water molecules.In order to prevent the excessive polarization of the charge and improve the accuracy ofthe force field in ABEEMσπ/MM fluctuating charge model, we have introduced a hydrogenbond fitting function klp, H(Rlp, H) in the hydrogen bond interaction region instead of the totalmodified coefficient k to describe hydrogen bonding interactions. I have selected eight smallmolecular dimer models. Then I fit the hydrogen bond fitting function in ABEEMσπ/MMmethod by fitting the binding energy of hydrogen bonds between the two regions at differentdistances in ab initio method. It shows that the binding energy of small molecular dimermodels by applying the hydrogen bond fitting functions in ABEEMσπ/MM method is similarwith the result in ab initio method. At the same time, the hydrogen bond lengths and bondangles of small molecule dimers in ABEEMσπ/MM method and ab initio method werecompared in order to further test the applicability of the hydrogen bond fitting functions. Theroot-mean-square deviation of bond lengths and bond angles are reasonable. The bindingenergy and the bond lengths and bond angles of dimers containing the same type of hydrogenbond are calculated in ABEEMσπ/MM method. The results are similar with the results of abinitio method. So these functions have good transferability.Each type of hydrogen bond has a set of hydrogen bonds fitting function parameterscorresponding to it. In order to calculate several types of hydrogen bonds with the sameparameters, I adjust these parameters and get the simple hydrogen bond fitting functionparameters. In ABEEMσπ/MM model, the dimers are optimized and calculated with thesimple hydrogen bond fitting functions. The binding energy of dimers is similar with theresult in ab initio method. The hydrogen bond lengths and bond angles in optimalconfiguration are also consistent with the results in ab initio method. Therefore, the simplehydrogen bond fitting functions have a good applicability.