Irradiation effect on secondary structure of protein induced by keV ions

Protein secondary structure changes by low-energy-ion irradiation are reported for the first time. The selected system is 30 keV N+ irradiation on bovine serum albumin (BSA). After irradiation at increasing fluences from 1.0 x 10(15) to 2.5 x 10(16)ion/cm(2), Fourier transform infrared spectra analysis was conducted. It was found that the secondary structures of BSA molecules were very sensitive to ion irradiation. Secondary conformations showed different trends of change during irradiation. With the increase of ion fluence from O to 2.5 x 10(16) ion/cm(2), the fraction of alpha -helix and beta -turns decreased from 17 to 12%, and from 40 to 31%, respectively, while that of random coil and beta -sheet structure increased from Is to 27%, and from 25 to 30%, respectively. Possible explanations for the secondary conformational changes of protein are proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.