Timofeev VP, Tkachev YV, Novikov VV, Alyoshkin VA, Lapuk VA. Is the Fab-Fragment from Monoclonal Rheumatoid IgM Flexible? A Spin Label Dynamics Study.
J Biomol Struct Dyn 2005;
23:175-81. [PMID:
16060691 DOI:
10.1080/07391102.2005.10507057]
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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.
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