[Modification of surface residues of lysine in immunoglobulin G using the spin marker 2,2,5,5-tetramethyl-3-maleimidopyrrolidine-1-oxyl].
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.
Lapuk
V A
VA
Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Varlamova
E Iu
EIu
Mozoleva
A P
AP
Anisimov
N V
NV
Timofeev
V P
VP
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
D003497:Cyclic N-Oxides; D007074:Immunoglobulin G; D013113:Spin Labels; C024516:N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)maleimide; D008239:Lysine