Relaxivity enhancement of low molecular weight nitroxide stable free radicals: importance of structure and medium.
The longitudinal relaxivities of seven water-soluble nitroxide derivatives of low-molecular weight have been measured at 5 degrees C and 37 degrees C in water and in serum between 0.01 and 200 MHz. The nuclear magnetic relaxation dispersion (NMRD) profiles show a clear relationship between the relaxivity observed in serum and the relative balance of the hydrophobic/hydrophilic character of the paramagnetic molecules. From the data analysis, contributions arising from a population of nitroxides characterized by reduced mobility can be extracted. The values of the correlation times are consistent with a system involving nitroxides adsorbed at the surface of albumin and magnetically interacting with the protons of hydrogen bonded water molecules.
Vallet
P
P
Department of Organic Chemistry, University of Mons-Hainaut, Belgium.
Van Haverbeke
Y
Y
Bonnet
P A
PA
Subra
G
G
Chapat
J P
JP
Muller
R N
RN
D003497:Cyclic N-Oxides; D005609:Free Radicals; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D009589:Nitrogen Oxides / Q000097:blood / Q000737:chemistry*; D013113:Spin Labels; D013329:Structure-Activity Relationship; D014867:Water
D003497:Cyclic N-Oxides; D005609:Free Radicals; D009589:Nitrogen Oxides; D013113:Spin Labels; D014867:Water; C003959:TEMPO