Chapter 1 - Two-Dimensional NMR Spectroscopy: A Graphical, “Top-Down” Description

Abstract

In this chapter, an introduction to the principles and uses of homonuclear and heteronuclear two-dimensional nuclear magnetic resonance (NMR) spectroscopy is presented. The pulse sequences and phase cycling procedures for a few of the most common experiments are analyzed in detail. The experiments are described by using a visual description of spin system evolution and coherence transfer processes. This method of description allows for the discussion of any multidimensional, multinuclear pulse sequence by a top–down approach. Two-dimensional NMR spectroscopy has become a mainstay experiment in many disciplines. The use of two- and higher- dimensional NMR has greatly advanced the applications of NMR to biochemical systems. Two-dimensional methods revolutionized the study of macromolecules by NMR spectroscopy. At the beginning of macromolecular NMR, the only options available to the scientist were one-dimensional spectra of well-resolved resonances. Any analysis of NMR experiments still requires well-resolved resonances; however, the resolution toolkit from which the spectroscopist can draw is much larger now. The current trend in the study of larger molecules is to obtain 3D, 4D, and even higher dimensional spectra of isotopically labeled molecules. The logic since higher resolution is required, however, does not leave two-dimensional NMR in the dust. It is always a good idea to obtain data from the simplest possible experiment. If the data can be unambiguously obtained from one-dimensional NMR spectrum, then there is no real need to use two-dimensional spectroscopy. Likewise, many problems associated with large molecular systems can be solved by simple two-dimensional methods.