High level density functional theory (DFT) calculations are performed for the first time to answer the question whether the arginine-carboxylate salt bridge stays in a zwitterionic state or a neutral one. The results ...High level density functional theory (DFT) calculations are performed for the first time to answer the question whether the arginine-carboxylate salt bridge stays in a zwitterionic state or a neutral one. The results indicate that in the gas phase, the neutral form is more stable and hence proton transfer occurs from guanidinium to carboxylate. However, in an aqueous solution the zwitterionic form should be favored. The difference might he caused by the electrostatic interaction between the salt bridge and its molecular environment. Therefore, the solvation effect has to be considered in the modeling of proteins, whose stabilization depends heavily on the salt-bridges.展开更多
The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem. In the present work, the zwitterionic and neutral forms of arginine-carboxylate salt bridg...The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem. In the present work, the zwitterionic and neutral forms of arginine-carboxylate salt bridge were studied by the B3LYP/6-311G(d,p)//PM3 method. It turns out that the neutral forms are more stable than the zwitterionic counterparts in gas phase. However, when bound by α-cyclodextrin, the zwitterionic forms become more stable than the corresponding neutral ones. It is suggested that the hydrophobic environment provided by the cyclodextrin cavity leads to such behavior. Therefore, the salt bridge still could be in a zwitterionic form in the hydrophobic interior of the real proteins.展开更多
文摘High level density functional theory (DFT) calculations are performed for the first time to answer the question whether the arginine-carboxylate salt bridge stays in a zwitterionic state or a neutral one. The results indicate that in the gas phase, the neutral form is more stable and hence proton transfer occurs from guanidinium to carboxylate. However, in an aqueous solution the zwitterionic form should be favored. The difference might he caused by the electrostatic interaction between the salt bridge and its molecular environment. Therefore, the solvation effect has to be considered in the modeling of proteins, whose stabilization depends heavily on the salt-bridges.
文摘The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem. In the present work, the zwitterionic and neutral forms of arginine-carboxylate salt bridge were studied by the B3LYP/6-311G(d,p)//PM3 method. It turns out that the neutral forms are more stable than the zwitterionic counterparts in gas phase. However, when bound by α-cyclodextrin, the zwitterionic forms become more stable than the corresponding neutral ones. It is suggested that the hydrophobic environment provided by the cyclodextrin cavity leads to such behavior. Therefore, the salt bridge still could be in a zwitterionic form in the hydrophobic interior of the real proteins.
