title: Identification of four major classes of sulfhydryl groups in human blood platelets. Ferricyanide titration of spin-labeled platelets.
abstract: Human blood platelets have been labeled with the sulfhydryl-specific spin labels, 4-iodoacetamido-2,2,6,6-tetramethylpiperidine-1-oxyl and 3-maleimido-2,2,5,5-tetramethylpyrrolidine-1-oxyl. First, the ESR spectra of platelets labeled with either reagent revealed two classes of sulfhydryl groups, a mobile class and an immobile class. Second, when spin-labeled platelets were titrated with high concentrations of potassium ferricyanide (greater than 10(-3) M), there was a decrease in the peak heights of the mobile class of sulfhydryl groups due to dipole-dipole exchange. Third, plots of peak heights of the mobile class versus ferricyanide concentration revealed three classes of mobile sulfhydryl groups compared to a single immobile class. This technique may be used to show the relative locations of spin-labeled groups on cell surfaces.
mesh_terms: D001792:Blood Platelets / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D005292:Ferricyanides; D006801:Humans; D007700:Kinetics; D013113:Spin Labels; D013438:Sulfhydryl Compounds / Q000097:blood*
chemical_list: D005292:Ferricyanides; D013113:Spin Labels; D013438:Sulfhydryl Compounds