The MALDI-TOF-MS (matrix assisted laser desorption ionization time-of-flight mass spectrometry) was carried out on a DYNAMO MALDI-TOF-MS (Thermo BioAnalysis, Santa Fe, New Mexico) with sinapinic acid matrix. Spectra were recorded in the dynamic extraction mode (setting 0.1) and calibrated externally using bovine serum albumin. The protein sample was mixed with a 1% solution of the matrix in 70% acetonitrile. 1 µl of this mixture was deposited to a probe, air dried and inserted into the mass spectrometer to acquire a spectrum. The inset shows the SDS polyacrylamide gel electrophoresis of this preparation (5 µg EPO) in comparison with 5 µg MPO. Electrophoresis was performed on boiled reduced samples. The first lane shows the migration of standard proteins.