Radiolysis of Amino Acids: A Study Using Raman Spectroscopy, Ultraviolet-Visible Spectrophotometry and Electrospray Ionization Mass Spectrometry

Abstract

Amino acids are basic components of proteins and play a critical role in the development and treatment of chronic diseases. Raman spectroscopy, as a non-destructive tool with little sample preparation, has been widely used in vitro and vivo studies. In the current study, twenty amino acids in solid state and aqueous/0.5 M hydrogen chloride (HCl) solution were previously irradiated to 10 kGy, 25 kGy and 50 kGy by electron beam and analyzed using Raman spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometry and electrospray ionization mass spectrometry (ESI-MS). Raman spectroscopy revealed spectral signatures of radiolysis of amino acids which related to the specific molecular vibration could be used for non-invasive analysis of radiation damage in vivo. Correlation between the absorbed dose and absorbance of amino acids was modeled by exponential saturation to explain the nature of radical production during irradiation. The results from ESI-MS revealed the modification of molecules after radiation. The relative stability to radiolysis of twenty amino acids was estimated from the results of those three techniques and compared with previous work. The ability of three techniques to identify and analyze the effects of radiolysis of amino acids in solution was evaluated. This first attempt to combine these three techniques to explore the radiation effect on amino acids, is promising for the further application in vivo studies.