title: [Modification of surface residues of lysine in immunoglobulin G using the spin marker 2,2,5,5-tetramethyl-3-maleimidopyrrolidine-1-oxyl].
abstract: Exposed lysine residues of human IgG were modified by a spin-label, 2,2,5,5-tetramethyl-3-male-imidopyrrolidine-1-oxyl at pH 9.2. Under these conditions, the degree of modification was about 10 lysine residues per protein molecule. The ESR spectrum of the spin-labeled immunoglobulin was much more mobile than that of spin-labeled immunoglobulin with the modification degree of about 1 residue that was obtained at pH 7.0. Thus, the sharp increase in the modification degree due to the increase in pH by two units leads to a marked loosening of the tertiary structure of the protein in solution, which is just indicated by the mobile ESR spectrum. Lithium chloride added to the solution of spin-labeled immunoglobulin induces a similar "immobilization" of its ESR spectra as sucrose.
authors.affiliation: Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia.
authors.forename: V A
authors.initials: VA
authors.lastname: Lapuk
authors.forename: E Iu
authors.initials: EIu
authors.lastname: Varlamova
authors.forename: A P
authors.initials: AP
authors.lastname: Mozoleva
authors.forename: N V
authors.initials: NV
authors.lastname: Anisimov
authors.forename: V P
authors.initials: VP
authors.lastname: Timofeev
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000737:chemistry*; D008239:Lysine / Q000737:chemistry*; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D007074:Immunoglobulin G; D013113:Spin Labels; C024516:N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)maleimide; D008239:Lysine