Study On The Charge And Structure By Using The Ab Initio Method And ABEEM?? Method

Zinc finger protein plays an important role in the process of gene expression,cell differentiation and embryonic development.This paper focuses on the theoretical study of the zinc finger protein with histidine and cysteine as the four coordinate.We cuts it into one layer,two layer and three layer zinc finger protein in order to calculate their charge distributions by making use of quantum chemistry method and atom-bond electronegativity equalization method(ABEEM??).Simultaneously,the atomic charges of the central region are extracted to be compared.The effect of one or two and three coordination of zinc finger on the ABEEM?? parameters is discussed.The ABEEM?? polarizable force field is employed to optimize the structure of zinc finger protein,and to compare it with crystal structure.1.The charge parameters of ABEEM?? method about zinc finger protein are determined,including reference charge,valence-state electronegativity,valence-state hardness.HF/STO-3G level is used to calculate Mulliken charge distribution of one layer,two layer and three layer zinc finger proteins.The parameters of ABEEM?? method,determined by using linear regression and least squares are used to obtain the charge distributions.The results which calculated by ABEEM?? method are in good agreement with those by ab initio method.The slope of the linear correlation equation of the charge distribution of ABEEM??method and ab initio is close to 1.000,the intercept is close to 0.0000,the linear correlation coefficient is over 0.9679.It can be demonstrated that the ABEEM?? method are reasonable and transferable.2.The effect of the size of the system studied on the charge distribution of the central part of zinc finger protein is investigated Although the number of layers and atoms is both different,the charge of the same atom in the central part has no significant change with the change of the number of layers.When we want to study other properties of zinc finger protein,from the point of view of the charge,we select one layer of zinc finger protein as its research object.3.The relationship between coordination number of zinc atom of zinc finger protein and its ABEEM?? parameters is discussed.Based on the structure in the real environment,the zinc finger protein of the four coordination position is decomposed into one coordination,two coordination and three coordination zinc finger protein.Using adjusted parameters,we compare the charge employing quantum chemistry method and ABEEM?? method.It can be obtained that this set of ABEEM?? parameters is suiTab.le for two coordination and three coordination zinc finger protein.As for one coordination zinc finger protein,we need to esTab.lish a new set of parameters.4.ABEEM?? polarizable force field is used by 19 zinc finger proteins after the appropriate force constants about bond length scaling and bond angle bending and balance of bond and angle are selected.The optimized structure is consistent with the crystal structure from the mean absolute deviation between the bond length and balance of bond length,as well as between the bond angle and balance of bond angle in central part.And parameters in the ABEEM?? polarizable force field can be applied to study the structure and properties of zinc finger protein.