[The functional differentiation of thymocytes under exposure to soluble H-2K k antigens released by macrophages in joint culture with the thymocytes].
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Animals↗
Biomedical subjects
I V Dudich
Publications and source records attributed to I V Dudich.
Slow conformational change in anti-dansyl antibody as a consequence of hapten binding: demonstration by ESR spectra.
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Animals↗
Rotational correlation times of IgG and its fragments spin-labeled at carbohydrate or protein moieties. Spatially fixed position of the Fc carbohydrate.
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Animals↗
[Study of the structural properties of recombinant gamma-interferon by circular dichroism and differential scanning microcalorimetry].
Recombinant human gamma-interferon is dimeric in solution at pH 7-4 as revealed by analytical gel-filtration. It was shown by circular dichroism that decreasing pH to 5.0 does not affect the secondary and tertiary structures of gamma-interferon macromolecule. It was established that heat denaturation process of gamma-interferon obeys the two-state transition model and can be described as the first-order reversible reaction. Temperature dependence of the denaturation-renaturation rate constants was shown to be consistent with the Arrhenius law. The equilibrium value of the denaturation temperature was found. Effective enthalpy of denaturation was determined both by thermodynamic and kinetic approaches. The data obtained showed that in the pH range 7-4 the dimeric IFN-gamma structure may be considered as a single cooperative thermodynamic domain. Thus, it may be concluded that gamma-interferon dimerization is necessary for the existence of the corresponding tertiary structure of the macromolecule.
Calorimetry, Differential Scanning↗
[Study of the structural properties of recombinant leukocyte interferon A by means of fluorescence polarization, circular dichroism, and differential microcalorimetry].
Human leukocyte interferon-A1 (IFN-alpha A) structure in solution was investigated by fluorescence polarization, circular dichroism and scanning microcalorimetry techniques. Using gel-filtration it was established that at neutral pH values and at concentration not exceeding 0.3 mg/ml IFN-alpha A has a dimeric configuration in solution. At pH below 5, IFN-alpha A exists as a monomer. Using circular dichroism technique the IFN-alpha A molecule was shown to preserve a native structure upon decreasing pH to 3.5. The rotational correlation time of IFN-alpha A molecule in dimeric and monomeric form was measured using fluorescence of DNS, conjugated with the protein, and fluorescence of tryptophan residues. Our data indicate that the shape of IFN-alpha A molecule may be approximated by the rigid ellipsoid of revolution with the axis ratio = 4:1. The intramolecular melting of IFN-alpha A was studied by scanning microcalorimetry and circular dichroism in the acidic pH range. Thermodynamic analysis reveals two independent cooperative transitions. These transitions can be explained by assuming that the IFN-alpha A molecule consists of two structural domains.
Calorimetry, Differential Scanning↗
[Polarity of the environment as a factor determining DNA conformation].
Polarity of double and ternary water-nonelectrolyte systems at the component ratio, corresponding to a half-transition point of DNA from B to A form was evaluated from ESR spectra of a spin-probe. In all cases examined the isotropic super-fine splitting constant (aN) is the same with an accuracy of 0.05 gauss. Small differences in aN are well correlated with the concentration of the groups which are able to form hydrogen bonds with the nitroxide fragment of the radical. Thus, media polarity is a factor which determines the A--B equilibrium of DNA in solution.
Chemical Phenomena↗
[Macromolecule rotative correlation time measurement by ESR for covalently bound spin label].
The dependence from temperature and viscosity of the shifts of the internal and external wide extremums in the ESR spectra of spin labelled bovine serum albumin has been studied. 2,2,6,6-tetramethylpiperidine-NI-oxyl-4-iodacetamide was used as a spin label. The obtained dependences was shown to be a consequence of the label participation in two types of rotations: an anisotropic fast rotation with tau less than 10(-9) sec relatively to a macromolecule, and the isotropic one with tau greater than 10(-8) sec due to rotation of the macromolecule itself. These conclusions were done on the basis of a model for complex rotation of the spin label. Comparison of theoretical and experimental data makes it possible to determined the correlation time for the protein moiety, to evaluate quantitatively the polarity of surroundings of the iminoxyl and to introduce a numerical parameter for the degree of mobility of the spin label relatively to protein molecule.
Electron Spin Resonance Spectroscopy↗