Density functional calculations of chemical shielding of backbone 15N in helical residues of protein G.

ABSTRACT: We performed density functional calculations of backbone (15)N chemical shielding tensors in selected helical residues of protein G. Here we describe a computationally efficient methodology to include most of the important effects in the calculation of chemical shieldings of backbone (15)N. We analyzed the role of long-range intra-protein electrostatic interactions by comparing models with different complexity in vacuum and in charge field. Our results show that the dipole moment of the alpha-helix can cause significant deshielding of (15)N; therefore, it needs to be considered when calculating (15)N chemical shielding. We found that it is important to include interactions with the side chains that are close in space when the charged form for ionizable side chains is adopted in the calcula

SUBMITTER: Cai L 

PROVIDER: S-EPMC2884268 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature