New routes to the detection of relaxation allowed coherence transfer in paramagnetic molecules.
A new pulse sequence is proposed to measure cross correlation rates between 1H Curie spin relaxation and 1H-15N or 1H-13C dipole-dipole coupling (%@mt;sys@%Gamma%@sx@%H,HX%@be@%CS,DD%@sxx@%%@mx@% ) in paramagnetic systems. The new sequence has been conceived to obtain quantitative measurements of cross correlation rates in the close proximity to the paramagnetic center, preventing the loss of information due to fast transverse relaxation. The approach was tested on the dicalcium protein calbindin D9k in which Ca2+ has been substituted at site II with Ce3+. At variance with previously reported experiments, all peaks observed in HSQC experiments tailored to paramagnetic signals give quantitative estimates of %@mt;sys@%Gamma%@sx@%H%@ital@%,%@rsf@%HX%@be@%CS%@ital@%,%@rsf@%DD%@sxx@%%@mx@% . This is crucial to refine the immediate proximity of the metal ion.
Kateb
Fathia
F
Magnetic Resonance Center, University of Florence, Via L. Sacconi 4, 50019 Sesto Fiorentino, Italy.
Piccioli
Mario
M
D064026:Calbindins; D002563:Cerium / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D064030:S100 Calcium Binding Protein G / Q000737:chemistry*
D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D002563:Cerium