Improved Description of Nuclear Magnetic Resonance Chemical Shielding Constants Using the M06-L Meta-Generalized-Gradient-Approximation Density Functional
Yan Zhao and Donald g. Truhlar
The performance of the M06-L density functional has been tested for four databases of NMR isotropic chemical shielding constants. Comparison with the B3LYP, BLYP, HCTH, KT1, KT2, LSDA, OPBE, OLYP, PBE, TPSS, and VSXC functionals shows that M06-L has improved performance for calculating NMR chemical shielding constants, especially for highly correlated systems. We also found that VSXC and M06-L have encouraging accuracy for calculating 13C chemical shielding constants, and both functionals perform very well for the chemical shielding constants in the o-benzyne molecule.
Polymorphism in an Amyloid-Like Fibril-Forming Model Peptide
René Verel, Ivan T. Tomka, Carlo Bertozzi, Riccardo Cadalbert, Richard A. Kammerer, Michel O. Steinmetz, Beat H. Meier
The structural basis for polymorphism in amyloids is unraveled with a model system. The hydrogen-bonding pattern within the sheets of fibrils is strongly influenced by the pH of the solution from which the fibrils are formed. Solid-state NMR spectroscopy experiments allow quantification of the relative amounts of two different -sheet structures over the pH range 2.0-7.3.