Nuclear magnetic resonance studies of the dynamic aspects of molecular structure and interaction in biological systems.

The applications of nuclear magnetic resonance spectroscopy to the study of structure and mechanism in biological systems are becoming increasingly wide­ spread. NMR is attractive because it offers straightforward techniques for the detailed investigation of the structure of both small and large molecules in solu­ tion as well as techniques for the study of the dynamic aspects of molecular struc­ ture and interaction. The biochemical applications of these techniques have been the subject of several reviews, where the emphasis has been mostly on the ap­ plications to structural analysis (1-12). In this review we concentrate on the application of NMR to the study of rate phenomena in biochemical systems. While the number of applications in this area lags behind the number of applications in the area of structural analysis, this field of investigation is becoming increasingly important. The theoretical develop­ ment of NMR methods for the study of rate processes and their applications exclusive of biochemical systems has been recently reviewed (13). After a brief discussion of the appropriate theoretical background and tech­ niques, this review has been rather arbitrarily divided into sections corresponding to the main areas in biochemistry where NMR methods have been applied. These include the helix-coil transition in polypeptides, conformational changes in bio­ macromolecules, and the interaction of small molecules with biomacromolecules. Not included in these sections are the applications using "paramagnetic probes" (6,8), which are discussed separately. This review is not intended to be complete but rather to illustrate the various possible applications of NMR methods to the study of kinetics and mechanism in biochemical systems, and to elucidate the important principles involved so that the reader can more readily understand the present applications and more care­ fully apply this technique to other systems. Many of the applications to date amount only to observations that the rate processes in the system under investiga­ tion are "on the NMR time scale." More detailed studies are beginning to appear,