High-Performance Liquid Chromatography-Mass Spectrometry Study of the Effect of Accelerated Electrons on the Structure of Bovine Serum Albumin

A method is proposed for the high-performance liquid chromatography-mass spectrometry quantification of the effect of an ionizing radiation dose on the structural characteristics of bovine serum albumin (BSA) in an aqueous solution by identifying unique peptides of the protein domain structures. BSA with an initial concentration of 500 mg/L in the physiological solution is irradiated with an accelerated electron beam with the maximum energy of 1 MeV and an average beam current of 1 pA at a dose rate of 18.5 Gy/s. The dose absorbed in the sample volume is estimated with a Fricke (ferrous sulfate) dosimeter. After irradiation of the BSA solution at doses of 0.3, 0.6, 1, 8, and 20 kGy, the structural integrity of the protein native form is analyzed and the protein content is quantified. To do this, the compounds with a mass of more than 30 kDa are removed by centrifugation, and then, BSA is subjected to enzymatic hydrolysis with addition of the trypsin solution, and the resulting peptides with a mass of more than 10 kDa are repeatedly removed. The samples obtained are examined by high-performance liquid chromatography-mass spectrometry. After that, the content of intact protein molecules is estimated by determining the concentrations of unique peptides corresponding to each of the three domains formed from the BSA amino acid sequence. Using the developed technique, a change in the natural conformation of the investigated protein (its denaturation) in water samples induced by ionizing radiation at a dose ranging from 0.3 to 20 kGy is established, on average, for 71% of protein molecules exposed to doses of up to 1 kGy, 79% of molecules exposed to doses of 4 kGy, and 99-100% of molecules exposed to doses of 8 and 20 kGy.