Fast calculation of C-13 NMR chemical shift tensors using the bond polarization model

The semi-empirical bond polarization theory was parametrized for the calcul ation of C-13 chemical shift tensors in systems with C-C, C-H, C-O and C-N single and double bonds. Calculations on bacteriochlorophyll and methyl bac teriopheophorbide led to a new suggestion of an assignment of the respectiv e NMR signals. Further more results for bacteriorhodopsin (bR) are presente d. The effect of the peptide environment on the retinal shift tensors in bR was quantified by comparative calculations. (C) 2001 Elsevier Science BN. All rights reserved.