engleski

Predicting CSAxDD Cross-Correlation Rates Using Fully Asymmetric CSA Tensors from DFT Calculations

Density Functional Theory (DFT) calculations were used to asses the dependence of backbone-atom chemical shielding anisotropy (CSA) on conformational parameters. The molecular models used in the simulation of protein secondary structure elements and CSA calculations were capped alanine dipeptide and octapeptide. The Gaussian98 program package was used for geometry optimization and NMR parameters calculation by DFT (B3LYP) employing the Gauge Invariant Atomic Orbital (GIAO) approach. In order to derive the cross correlation rate (Eq. 1) as a function of conformation, we compare the cross correlation rates predicted using the fully anisotropic CSA tensor through Eq. 2 instead of Δ σ S P2(cosθ 3, SI) (Eqs. 3, 4), which neglects the asymmetry. The results obtained on backbone 1H, 13C and 15N CSA tensors showing dependence on protein secondary structure is visualized by way of Ramachandran type diagrams for the dipeptide model. Acknowledgement This work was supported in part by the Lise Meitner fellowship of the Austrian Science Fund (FWF M677), FWF project P15380, Austrian Croatian joint research project 911-02/03-06 (ÖAD-Project 13/04), and the Ministry of Science, Education and Sport of the Republic of Croatia project P0098059.

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