Ab initio studies of gas phase asparagine conformers

Systematic and extensive conformational search of the gas phase asparagine has been performed for the first time. A total of 972 unique trial structures were generated by allowing for all combinations of internal single-bond rotamers. All the trial structures were optimized at the B3LYP/6-311G* level of the theory and then subjected to further optimization at the B3LYP/6-311++G** level and a total of 62 conformers were found. Single-point energies were also calculated at the MP2/6-311++G** level of theory. The relative energies, rotational constants, dipole moments, zero-point vibrational energies and some harmonic frequencies are listed for the conformers. The conformational distributions of the gas phase asparagine at various temperatures were calculated.