Deuterium (2H) NMR was used to investigate the interaction of L-Phenylalanine [with aromatic protons replaced by deuterons (Phe-D5)], with 5′-AMP and polyadenylic acid (poly A). A considerable change in line width of the aromatic deuteron signals of Phe was observed. These data were plotted using a Scatchard-type equation, and yielded apparent binding constants for L-Phe to 5′-AMP and poly A of 7 and 11 M-1, respectively. Future applications of 2H-NMR in the study of nucleic acid-protein interactions are discussed. © 1982.