Homonuclear Hartmann-Hahn Magnetization Transfer: New One- and Two-Dimensional NMR Methods for Structure Determination and Spectral Assignment

Abstract

The idea of two-dimensional (2D) Fourier transform NMR, first introduced by Jeener (1) has proven to be very powerful for analyzing the NMR spectra of compounds of high complexity. The general theory of 2D NMR was described by Aue et al. (2) in 1976, and has provided the theoretical basis for the development of a large number of new one- and two-dimensional pulse schemes. Nonetheless, the pulse scheme originally proposed by Jeener, and described in great detail by Aue et al. is currently still one of the most widely used 2D methods. Some minor modifications have been made to this experiment to facilitate data handling and processing (3,4) and to enhance the resolution by recording double quantum filtered absorption mode spectra (5,6). Jeener’s experiment is generally referred to as the COSY (Correlated Spectroscopy) method, and has been applied to a variety of problems, varying from small organic molecules to biological macromolecules. The COSY spectrum displays the presence of scalar coupling between coupled spins A and X by the presence of a so-called cross peak centered about the frequency coordinates (F₁,F₂) = (v _A,v _X) and (v _X,v _A), where v _A and v _X are the chemical shift frequencies of spins A and, X respectively.