title: Is the Fab-fragment from monoclonal rheumatoid IgM flexible? A spin label dynamics study.
abstract: A comparative study of the Fab- and Fab-RF-fragments in the molecules of monoclonal IgM and IgM-RF, respectively, was performed by the spin label method. The spin label, 2,2,6,6-tetramethyl-4-dichloro-triazinylaminopiperidine-1-oxyl, was introduced into the peptide part of the protein. On the basis of the data on the temperature-viscosity dependences of the EPR spectral parameters of the resultant spin-labeled proteins, the rotational correlation time tau of the spin carrier was determined. It turned out that the reduced to normal conditions tau values for the molecules of the Fab- and Fab-RF-fragments were 21+/-2 and 11+/-1 ns, respectively. Analysis of the resultant data provides sufficient grounds for assuming that such a sharp decrease in the tau value for the molecule of the Fab-RF fragment is due to local flexibility of its globular structure, which, in turn, can determine the specific features of the IgM-RF functioning as an autoantibody.
authors.affiliation: VA Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, 119991 Moscow, Russia. tim@eimb.relarn.ru
authors.forename: V P
authors.initials: VP
authors.lastname: Timofeev
authors.forename: Ya V
authors.initials: YV
authors.lastname: Tkachev
authors.forename: V V
authors.initials: VV
authors.lastname: Novikov
authors.forename: V A
authors.initials: VA
authors.lastname: Alyoshkin
authors.forename: V A
authors.initials: VA
authors.lastname: Lapuk
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D007075:Immunoglobulin M / Q000737:chemistry*; D013113:Spin Labels; D013816:Thermodynamics
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D007075:Immunoglobulin M; D013113:Spin Labels