NMR as a Structural Tool for Macromolecules: Current Status and Future Directions

The contemplation of truth and beauty is the proper object for which we were created, which calls forth the most intense desires of the soul, and of which it never tires -Hazlitt In his Nobel lecture Purcell commented that when he saw snow in New England after the discovery of NMR, it appeared like "heaps of protons quietly precessing in earth's magnetic field. " If he were to make the comment in the context of how NMR is being used today, he could have conjured up an image of hydrogen, carbon, and nitrogen nuclei in proteins of an earthbound 8rganism subtly orchestrating a quiet symphony of frequencies, from 150 Hz to 2 kHz, carrying clues to the three-dimensional structure of the macromolecules. The manner in which the basic discoveries of Bloch and Purcell have led to the emergence of NMR, several decades later, as a major technique of biological and medical physics (and chemistry) is a striking example of the power of basic research. It is also a fascinating saga whereby whenever it was felt that the field had reached a plateau, new directions, new technologies, and sometimes serendipity produced new developments that revolutionized the technique and enhanced its capability. As Richard Ernst points out "NMR is intellectually attractive, . . . the practical importance of NMR is enormous, and can justify much of the playful activities of an addicted spectroscopist" (Nobel lecture).