In my thesis I shall focus on the development of new NMR experimental methods to study structure and internal motions of two kinds of biological polymers, viz. proteins and nucleic acids. I shall investigate the anisotropic local motions of peptide planes and locate amide protons in proteins by measuring three dipole-dipole cross-correlated relaxation rate constants of single-quantum coherences involving the peptide backbone nuclei. I shall also estimate the internucleotide hydrogen bond lengths in nucleic acids from the measurement of the longitudinal auto-relaxation rate constants of both donor and acceptor nitrogen-15 nuclei of Watson-Crick base pairs. Finally I shall measure and discuss the temperature dependence of internucleotide nitrogen-nitrogen scalar couplings in nucleic acids.