ABOUT NEW UNIVERSAL APPROACH TO THE EPR-SPECTRA SIMULATION OF THE SPIN-LABELED MACROMOLECULES

The article describes the model of the spin label behaviour, where the spin label attached to the protein aminoacid residue simultaneously accomplishes two different motions: the fast anisotropic reorientation of the label itself (with tau << 1 nsec) relative to the protein molecule and the slow isotropic diffusion (with tau > 5 nsec) of the very protein molecule. A new way of description of the nitroxide group fast anisotropic motion is introduced. All the spin-labeled macromolecules of the sample are grouped into subensembles according to the similarity of their dynamic properties. Similarity of dynamic properties is expressed through the identical partial averaging of the nitroxides' magnetic magnitudes. Averaging in every subensemble is characterized by discrete parameter couple - S and k. The resulting EPR spectrum of the entire spin system is, therefore, a weighted superposition of spectra received from every subensemble. For implementation of this approach a number of computer programs was designed. Examples of spectra simulations are given for the following spin-labeled macromolecules: Hemoglobin (Hb), Immunoglobulin G (IgG) and Poly-gamma-benzylgluthamate (PGBG). The listed results confirm universality and advantages of this method.