V. D. Fedotov

Structures and dynamics of bulk polymers by NMR-methods

In recent years the development of the NMR method has been closely linked to the creation of the theory of the NMR in solids and with the elaboration on their basic principles and methods of high resolution in solids. The aim of this volume is to explain simply and clearly the principles for the understanding of the NMR in solid polymers, to show what kind of information can be gained using NMR investigations of bulk polymers, and to demonstrate the ways of obtaining this information, their correctness and their place in comparison with other methods. The discussion is restricted to the most important and typical nuclei 1H, 13C, and (briefly) 2D, and, in connection with that, to the dipolar and quadrupolar interaction and to the chemical shift.

Time domain dielectric spectroscopy. A new effective tool for physical chemistry investigation

The general principles of time domain dielectric spectroscopy (TDS) are summarized. The methods of data treatment and presentation, and different TDS methods which enable one to obtain the permanent spectrum of ε* (ω) in the frequency range of 105–1010 are given. The examples of TDS application for the investigation of dielectric properties in samples of different nature and structure are considered in this review.

A Fourier transform pulsed-gradient spin echo nuclear magnetic resonance self-diffusion study of microemulsions and the droplet size determination

Abstract Self-diffusion of all components in two different microemulsions has been studied by the Fourier-transform pulsed-gradient spin echo 1 H nuclear magnetic resonance technique. The analysis of hydrodynamic and direct droplet-droplet interactions in microemulsions allows the simultaneous application of the Stokes-Einstein equation for surfactant and oil. The result of this analysis is a simple relation connecting self-diffusion coefficients of components and the size of droplets. It is shown that because of partial solubilization of water in oil the droplet radius can be significantly different from the expected radius.

Self-diffusion in microemulsions and micellar size

Self-diffusion of all components of two different microemulsions have been measured. Application of Stokes-Einstein equations for surfactant and oil gives a simple relation connecting their size and self-diffusion coefficients. Using the measured self-diffusion coefficients and dimensions of oil molecules known from elsewhere, the size of the surfactant droplets was estimated. This approach turns out to be advantageous in practical determination of droplet size in microemulsions.

DYNAMIC STRUCTURE OF PROTEINS IN SOLID STATE. 1H AND 13C NMR RELAXATION STUDY

Temperature dependencies of 1H non-selective NMR T1 and T2 relaxation times measured at two resonance frequencies and natural abundance 13C NMR relaxation times T1 and T1r measured at room temperature have been studied in a set of dry and wet solid proteins - Bacterial RNase, lysozyme and Bovine serum albumin (BSA). The proton and carbon data were interpreted in terms of a model supposing three kinds of internal motions in a protein. These are rotation of the methyl protons around the axis of symmetry of the methyl group, and fast and slow oscillations of all atoms. The correlation times of these motions in solid state are found around 10(-11), 10(-9) and 10(-6)s, respectively. All kinds of motion are characterized by the inhomogeneous distribution of the correlation times. The protein dehydration affects only the slow internal motion. The amplitude of the slow motion obtained from the carbon data is substantially less than that obtained from the proton data. This difference can be explained by taking into account different relative inter- and intra- chemical group contributions to the proton and carbon second moments. The comparison of the solid state and solution proton relaxation data showed that the internal protein dynamics in these states is different: the slow motion seems to be few orders of magnitude faster in solution.

NMR and dielectric spectroscopy investigation of protein dynamical structure.

Abstract The general approach to globular proteins dynamical structure investigation by NMR and time domain dielectric spectroscopy (TDDS) is presented. The information on macromolecular dynamical behavior in the case of these two methods is obtained in terms of correlation function and its parameters of atom motions. The interpretation of experimental results in the present work will be carried out in the framework of model-free approach which is common both for magnetic and dielectric relaxation. The lysozyme pH-dependence investigation is presented as an example.

New Modification of Model-Free Approach to Analysis of Nuclear Magnetic Relaxation Data in Proteins

A formal approach to the analysis of 13C magnetic relaxation data in proteins has been developed. It is based on the concepts of one of the authors on the internal motions in solid polymers (Fedotov, V.D., Pulse NMR in bulk polymers, Doctoral dissertation, Kazan, USSR, 1981). According to this approach the intermolecular motions in proteins are considered as anisotropic ones and described in terms of a spectrum of correlation times. To characterize the motions a set of formal microdynamic parameters has been introduced. They are: the anisotropy parameter (a measure of spatial restriction of motion), the most probable correlation time, the parameter of the correlation time distribution width. The analysis of protonated carbon relaxation in globular proteins (bovine pancreatic trypsin inhibitor and ribonuclease S) and polymers has been carried out by the model-free approach. Microdynamic parameters of CH3-, CH2-, aromatic CH-groups have been considered within the framework of the diffusional rotation-oscillation models. To explain the backbone CH-group relaxation the model of the defect diffusion has been applied. The distinctive feature of the results obtained is the broad correlation time distribution for all groups of any type. The causes of nonexponential correlation function of local motion have been discussed. To elucidate the nature of the correlation time the carbon magnetization decays in the wide range of microdynamic parameter values imitating various experimental conditions have been calculated.

Structure and dynamic behavior of protein molecules in solution

The results of the investigation of structure and dynamic behavior of protein in solution by time-domain dielectric spectroscopy are presented. The dipole correlation functions for myoglobin, lysozyme and RNase A solutions at different concentration, pH and temperature were obtained. The processes of the intramolecular interactions of myoglobin molecules, the pH-induced dimerization of lysozyme and thermal denaturation of RNase A are discussed.

Dielectric relaxation, rotational diffusion and the heat denaturation transition in aqueous solutions of RNAse A

Abstract The heat denaturation transition of pancreatic RNAse A was investigated by time-domain spectroscopy. In the temperature interval 5–90°C the protein molecule may be in three states: native, temperature denaturated and unfolded. The heat denaturation process occurs in two stages: In the first stage the system behaves as a macromolecule, maintaining its globular structure and increasing its volume two times and its dipole moment 1.5 times; in the second stage the transition into a statistical coil state Occurs.

1H and13C nuclear magnetic relaxation and local dynamics of lysozyme and synthetic polypeptides

The combined analysis of1H and13C NMR relaxation data in solid lysozyme and some typical homopolypeptides was carried out by using “model-free” approach. Three types of relaxation transitions (γ’, γ and β) were revealed in the temperature range investigated. The microdynamical parameters of these motions were determined. From the comparison of these parameters with those of selected synthetic polymers it follows that the molecular motions in proteins and synthetic polymers are of the same nature. All these motions show pronounced anisotropic character. In the investigated temperature range no molecular motions corresponding to α-relaxation (liquid-like) transition were revealed. The hydration effects on parameters of the motions in proteins were considered. The most pronounced effect takes place for β-transition. The effect of Brownian rotation of protein molecule in solution on measured correlation function of local motions was also discussed.