Effect of the preliminary irradiation of bovine serum albumin (BSA) in the terahertz spectral range on the conformation changes revealed with the help of EPR spectroscopy was investigated using the spin probing technique. The formation of the spin probe occurs directly in the aqueous solution of BSA from a nitrone compound (dihydropyrazine dioxide). It was shown that irradiation causes changes in the parameters of the EPR spectrum of the spin probe. An approach to linking the observed changes with the structural characteristics of reaction centres - the functional groups of amino acids comprising BSA - was outlined.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.