Analysis of dipolar-coupling-mediated coherence transfer in a homonuclear two spin-1/2 solid-state system

Homonuclear dipolar-mediated coherence transfer (DCT), a through-space tran sfer of magnetization between like spins, can yield otherwise difficult-to- obtain structural information for macromolecules by measuring the internucl ear distances between two sites of interest. The behavior of a spin-1/2 sys tem under DCT is analyzed in detail by computing the time development of th e density matrix using the product operator formalism. The effect of cohere nce transfer (CT) via the homonuclear isotropic scalar coupling on DCT is e xamined, Analytical and computational results that yield useful information on the frequencies, first-maxima, and first-zero of CT for a uniaxially or iented or a single-crystal solid-state system are presented. The results pr edict that the evolution of the spin angular momentum operators under the h omonuclear dipolar coupling Hamiltonian leads to "cylindrical mixing" unlik e "isotropic mixing" due to the strong scalar coupling Hamiltonian. These r esults will find relevance in both the design of RF pulse sequences for the structural studies of uniaxially oriented biological solids and the interp retation of solution NMR results from proteins embedded in partially orient ed bicelles. (C) 1999 Academic Press.