Comparative Studies on the Stable Conformers of Arginine in Aqueous Solution: A Theoretical Study

초록

Arginine is one of the most interesting amino acids because it is able to form a stable zwitterion species in the gas phase due to its extremely basic guanidine side chain (-(CH2)3-NHC-(NH2)NH). Therefore arginine has been the subject of many intensive experimental and theoretical studies, but most theoretical works have focused on the stable conformers in the gas phase. Moreover, very little theoretical work has been done for transformations between these conformers. In this work, various conformers of arginine and transition structures for the interconversions among these conformers were studied theoretically at the MP2/6-311+G(d,p) level of theory in the gas phase and in aqueous solution. For studies in aqueous solution, the structures have re-optimized by use of the conductor-like polarizable continuum model (CPCM) with the PAULING cavity model. The energetics were then refined using the CCSD(T)/6- 311+G(d,p) level on geometries optimized at the MP2 level. All calculations were performed with Int(grid=ultrafine) option by using the Gaussian-09 program.