Recoupled polarization transfer heteronuclear H-1-C-13 multiple-quantum correlation in solids under ultra-fast MAS

A new approach for high-resolution solid-state heteronuclear multiple-quant um MAS NMR spectroscopy of dipolar-coupled spin-1/2 nuclei is introduced. T he method is a heteronuclear chemical shift correlation technique of abunda nt spins, like H-1 with rare spins, like C-13 in natural abundance. High re solution is provided by ultra-fast MAS and high magnetic fields, high sensi tivity being ensured by a direct polarization transfer from the abundant pr otons to C-13. In a rotor-synchronized variant, the method can be used to p robe heteronuclear through-space proximities, while the heteronuclear dipol ar coupling constant can quantitatively be determined by measuring multiple -quantum spinning-sideband patterns. By means of recoupling, even weak hete ronuclear dipolar interactions are accessible. The capabilities of the tech nique are demonstrated by measurements on crystalline L-tyrosine hydrochlor ide salt. (C) 1999 Academic Press.