Cross-correlation between the fluctuations of C-13(alpha)-H-alpha interactions affects the relaxation behavior of two-spin coherences (zero- and double-quantum coherences) involving the C-13(alpha) nuclei of two successive amino acid residues. The cross-correlation rates are shown to depend on a dihedral angle Sigma defined by two planes subtended by the atoms {H-alpha(i-1),C-13(alpha)(i-1),C-13(alpha)(i)} and {C-13(alpha)(i-1),C-13(alpha)(i),H-alpha(i)}, This dihedral angle is related to the secondary structure of a protein, and can be used as a constraint in various protein structure calculation protocols.