Biomedical subjects
Publications and source records attributed to V S Khristoforov.
Data on NMR-spectroscopy studies of the structure-function interrelation in immunoglobulins G and their proteolytic fragments are reviewed. Relationship between structural and dynamic characteristics of immunoglobulins G and their functional properties is discussed.
Conformational properties of the Fc- and pFc'-fragments of human myeloma immunoglobulins G of the first and third subclasses were studied by 1H-NMR method (270 and 400 MHz). It was found that the globular structures (domains) of the Fc-fragments of IgG1 and IgG3 in solution are characterized by high segmental mobility, and have no significant differences in their spatial arrangement. Comparative analysis of the spectra obtained at different temperatures (30-70 degrees C) revealed that the Fc-fragment of IgG3 has a more heat-stable conformation than the Fc of IgG1. The intramolecular mobility of the Fc-fragment increased upon lowering the pH. The partial assignment of the signals in the NMR spectra of the Fc-fragments of immunoglobulins G1 and G3 was carried out, and the pKa values for histidines of the pFc'-fragment of IgG1 were determined.
Explore the source record for details and available documents.
The structural properties of globular proteins analyzed by two different methods: high-resolution NMR and circular dichroism were compared. We established that the spin diffusion method shows changes in the secondary structure during the unfolding of the alpha-lactalbumin molten globule by urea. It was shown that the spin diffusion method is extremely effective in studies of interactions of water and denaturant molecules with the protein both in the native and the molten globule states.
Carbonic anhydrase B unfolding with urea (pH 5.7, T = 298 K) was studied by high-resolution NMR spectroscopy. The effectiveness of spin-diffusion influencing compactness of the protein molecule can be described with the rigidity parameter G. Parameter G displays sigma-like characteristic behavior when concentration increases. The ratio between integral intensities of urea and protein signals in spin-diffusion and normal 1D spectra are the same. This suggests that there is no predominant urea-protein molecular interaction. The concentration of large protein-solvent associates increases rapidly at urea levels of 4.2-6.2 M implying that protein molecule shifts to a molten globule state. Protein-solvent associates are dissipating with urea concentration increase to above 6.6 M when carbonic anhydrase B polypeptide chain is completely unfolded.
The rigidity parameter (G), which is characteristic of protein compactness, was studied in native globular carbonic anhydrase B. The dependence of parameter G on power and excitation time of spin-diffusion was expressed analytically. We found out that native carbonic anhydrase B is able to form water-protein units that are probabilistically distributed with respect to their sizes. Large water-protein units can be detected by analyzing the spin-diffusion spectra. The excitation frequencies of spin-diffusion spectra were shifted far away from typical 1H NMR spectra of carbonic anhydrase B.
The formation of carbonic anhydrase B associates (pH 5.7, urea concentration 4.2 M, 297 K) was studied as a function of protein concentration and time by nuclear magnetic resonance spectroscopy (spin diffusion method). It was found that the association process proceeds in two steps. The first step is relatively fast and cannot be controlled by our methods. During this step, persistent units are built. These consist of protein molecules that are able to interact with solvent molecules and with each other when protein solution contains 4.2 M of urea. Persistent units are relatively small (two, three protein molecules), and their mobility matches one of a single protein. The second step is slower, and throughout this step large structures are formed from persistent units. The parameters G* and S*, which characterize spin diffusion in a protein and a solvent, respectively (when spin diffusion excitation happens away from NMR spectral signals) are related to the probable size distribution of protein-solvent associates and are determined by their collective properties.
Explore the source record for details and available documents.
Synthetic decapeptide corresponding to ACTH-like sequence of the variable part of the heavy chain of immunoglobulin G1 Eu was studied by two-dimensional 1H-NMR spectroscopy (400 MHz). A complete assignment of signals in the peptide spectrum was made. The decapeptide was shown not to have any ordered spatial structure, and was characterized by a high extent of flexibility of the oligopeptide chain, except for the peptide bond with an N-terminal residue.
A high degree of correlation between the capability of subclasses of human immunoglobulins G to form aggregates due to thermal treatment, and their complement-binding activity was established. On the basis of the experimental data obtained by the methods of light scattering, circular dichroism, microcalorimetry, it was supposed that "hinge" region of immunoglobulins G participates in the initial stage of thermal aggregation and in the activation of the process of complement binding.
Conformational and dynamic properties of the synthetic peptides, amino acid sequence of which correspond to biologically active fragments of the following human cytokines: alpha 2, gamma interferons and interleukins 1 beta, 2, were studied in aqueous solution and dimethylsulfoxide by one-dimensional and two-dimensional 1H-NMR spectroscopy (400 MHz). The analysis of nuclear Overhauser effect data, values of vicinal J3(NH-C alpha H) coupling constants of amide protons and their temperature coefficients of chemical shifts indicate an unordered flexible conformation of the peptides in aqueous solutions. The structural and dynamic features of the peptides investigated are discussed together with their biological activity.
A comparative study of the conformational and dynamics properties of the ACTH-like linear peptides, sequences of which correspond to amino acid residues 11-20 of the heavy chain of human immunoglobulin G1 Eu, residues 78-85 of human pro-interleukin-1 alpha and site 10-18 of human ACTH, was performed in aqueous solution and dimethylsulfoxide by 1H-NMR spectroscopy at 400 MHz. The peptides were shown to possess an unordered unfolded flexible conformation in aqueous solution. The revealed structural and dynamic features of the peptides are discussed together with biological activity of this class of compounds.