NUCLEIC ACIDS: A NUCLEAR MAGNETIC RESONANCE STUDY.

Single-stranded nucleic acids in aqueous media exhibit proton magnetic resonance spectra with acceptable signal-noise ratios if multiple scans of the spectra are stored in and subsequently read out of a computer of average transients. Partial ordering of the adenine bases of polyadenylic acid in solution is reflected in contributions to the chemical shifts that are removed on "melting." More significantly, secondary structure such as occurs in complexes ofpolyA and polyU and in double-stranded DNA is manifested in proton magnetic resonance spectrabelow the "melting" temperature by severe resonance line broadening which results from anisotropic nuclear dipole-dipole interactions. The proton resonances are narrowed in and above the "melting" region, and measurement of integrated resonance intensities can give insight into quantitative aspects of hybridization, "melting," and other nucleic acid interactions.