Is the Fab-Fragment from Monoclonal Rheumatoid IgM Flexible? A Spin Label Dynamics Study

• Published in: Journal of biomolecular structure & dynamics 2005-10, Vol.23 (2), p.175-181
• Main Authors: Timofeev, V. P., Tkachev, Ya. V., Novikov, V. V., Alyoshkin, V. A., Lapuk, V. A.
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal - chemistry; Arthritis, Rheumatoid - immunology; Electron Spin Resonance Spectroscopy; Humans; Immunoglobulin Fab Fragments - chemistry; Immunoglobulin M - chemistry; Spin Labels; Thermodynamics
• ISSN: 0739-1102; 1538-0254
• DOI: 10.1080/07391102.2005.10507057

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 T of the spin carrier was determined. It turned out that the reduced to normal conditions T 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 T 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.