Fluorescence polarization analysis of various immunoglobulins Dependence of rotational relaxation time on protein concentration and on ability to precipitate with antigen

Rotational correlation times of IgG and its fragments spin‐labeled at carbohydrate or protein moieties Spatially fixed position of the Fc carbohydrate

“…The increase of viscosity by addition of sucrose above 45% produces a sharp rise of the 2,4 ' values due to the strong immobiliza. tion of the relative spin-label rotation (2A ' ~-2A z)-The values of r obtained for IgG-SLII, F(ab')2-SLII and Fab'-SLII correspond well to the values of r Table 1 Parameters of ESR spectra and rotational relaxation times (r) of spin-labeled proteins a 2A' was measured using the plots in fig.3 at (T/n)=300 (corresponding to 20°C and 0% sucrose concentration) in this study for IgG as well as for the fragments correspond well to values obtained by fluorescence depolarization measurements [11][12][13][14]. According to X-ray data [ 15] Fc fragment is less compact than Fab fragment.…”

Spin‐label study of segmental flexibility of anti‐hapten antibodies

“…The absolute values of the rotational correlation times obtained in this study and in the study employing fluorescence polarization [3] are different (19 and 29 ns versrs 40 and 60 ns) in contrast to the similarity between the r values for immunoglobulin G Definitions: H'(-1), the distance of high-field A, or A, extrema from the central line determined at 20°C and 0% sucrose, i.e., T/q = 300 (see fii.2);H(-l), extrapolatedvaIueofH' (-1) at a+-,i.e., T/q=O(seefig.2);AH(-l)=H(-1) -H'(-1), shifts of high-field extrema used for calculations of the r values (see text)…”

“…For example, cleavage of the inter-heavy chain disulfide bonds that results in conversion of incomplete rabbit antibodies into direct hemagglutinins points to an important role of Fab-parts movement [2]. In [3] we found by a fluorescence polarization method that precipitating pig anti-Dnp antibodies, randomly labeled by dansylchloride, had a more flexible structure than nonprecipitating antibodies with the same specificity. The segmental flexibility of macromolecules can be determined by the spin-label method also [4].…”

Nonprecipitating pig anti‐dinitrophenyl antibody: Factors influencing the conversion into precipitating antibody

“…Complexes of nonprecipitating (Np) antibody with DNP-coupled serum albumin were found to consume complement nearly as effectively as analogous complexes of a precipitating antibody [3]. Our suggestion that the early precipitating and late Np antibodies represent subclasses of pig IgG differing in the shape and/or segmental flexibility of the molecule [l] has recently found support by studies employing small-angle neutron scattering [4, 51 and fluorescence depolarization [6].…”