13C-detected through-bond correlation experiments for protein resonance assignment by ultra-fast MAS solid-state NMR.
Résumé
We present two sequences which combine ((1)H,(15)N) and ((15)N,(13)C) selective cross-polarization steps with an efficient variant of the J-based homonuclear transfer scheme, in which a spin-state-selective (S(3)E) block is incorporated to improve both resolution and sensitivity in the direct (13)C dimension. We propose these two sequences as a part of a suite of four N-C correlation experiments allowing for the assignment of protein backbone resonances in the solid state. We illustrate these experiments under ultra-fast magic angle spinning conditions on two samples of microcrystalline dimeric human superoxide dismutase (SOD, 153×2 amino acids), in its diamagnetic ("empty", Zn(II)) and paramagnetic (Cu(II), Zn(II)) states.
Mots clés
J-coupling
paramagnetism
solid-state nuclear magnetic resonance spectroscopy
superoxide dismutase
magic angle spinning
ANGLE-SPINNING NMR
ZINC SUPEROXIDE-DISMUTASE
J COUPLING-CONSTANTS
CORRELATION SPECTROSCOPY
CROSS-POLARIZATION
PROTONLESS NMR
PARAMAGNETIC METALLOPROTEINS
MICROCRYSTALLINE PROTEIN
C-13
RESOLUTION