Effect of temperature on labelled BSA structure: EPR study

Bovine serum albumin (BSA) was labelled with 3-maleimido-proxyl (3-maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxy). The electron paramagnetic resonance spectra of labelled protein were recorded in temperature range 300-340 K on a Bruker X band spectrometer. The temperature changes in EPR Spectrum parameters such as rotational correlation time, s/w and 2A(II) parameters were assigned to the increasing mobility of the fragment of the polypeptide chain which contained a spin marker. The order parameters depend not only on temperature but also on the concentration of the labelled protein.