Structures of protonated arginine dimer and bradykinin investigated by density functional theory: further support for stable gas-phase salt bridges.

ABSTRACT: The gas-phase structures and energetics of both protonated arginine dimer and protonated bradykinin were investigated using a combination of molecular mechanics with conformational searching to identify candidate low-energy structures, and density functional theory for subsequent minimization and energy calculations. For protonated arginine dimer, a good correlation (R = 0.88) was obtained between the molecular mechanics and EDF1 6-31+G* energies, indicating that mechanics with MMFF is suitable for finding low-energy conformers. For this ion, the salt-bridge or ion-zwitterion form was found to be 5.7 and 7.2 kcal/mol more stable than the simple protonated or ion-molecule form at the EDF1 6-31++G** and B3LYP 6-311++G** levels. For bradykinin, the correlation between the molecular mechanics

SUBMITTER: Strittmatter EF 

PROVIDER: S-EPMC1434516 | biostudies-literature | 2000 Jun

REPOSITORIES: biostudies-literature