AB-INITIO CALCULATION OF THE NMR SHIELDING CONSTANTS FOR HISTAMINE

The gage-independent atomic orbital (GIAO) approach is used within the coupled Hartree-Fock approximation to compute the H-1, C-13 and N-15 NMR shielding constants in two tautomeric forms of both the histamine molecule and its protonated form. An analysis of the results shows tha t the protonation on the end of the chain changes its nitrogen shieldi ng constants of the pyridine and pyrrole type. These changes are much higher for the N(3)-K than for the N(1)-H tautomer. (C) 1997 Elsevier Science B.V.