Applications of natural-abundance nitrogen-15 nuclear magnetic resonance to large biochemically important molecules.

Natural-abundance nitrogen-15 nuclear magnetic resonance spectroscopy of enzymes and other biopolymers is found to be feasible using newly available instrumentation. The long correlation times of such molecules result in short spin-lattice relaxation times, and these in turn allow rapid signal accumulation. The advantages of short T1 values are sometimes offset, however, by unfavorable nuclear Overhauser effects. The dependence of T1 and nuclear Overhauser effects upon correlation time is discussed, and preliminary nitrogen-15 nuclear magnetic resonance results for several biopolymers, including lysozyme, protamines, pepsin, hemoglobin, vitamin B 12, and tRNA, are presented.