Institution: | aCollege of Chemistry, Jilin Province Research Center of Engineering and Technology for Spectral Instruments, Jilin University, Changchun 130021, P. R. China bApplied Chemistry Department, East China University of Technology, Fuzhou 344000, P. R. China cCollege of Information Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China dBeijing Physical and Chemical Analysis Center, Beijing 100089, P. R. China |
Abstract: | Serine, one of the nonessential amino acids, is of principal interest because of its capability to form magic-number ionic clusters, which provide a remarkable preference for homochirality. With L-aspartic acid as the precursor,this study provides experimental evidence for serine formation in weak acidified aqueous solutions in the presence of iron, with exposure to sunlight, which simulates the natural conditions of the prebiotic aqueous environment. The resultant mixture is directly analyzed via desorption electrospray ionization mass spectrometry( DESI-MS), without any sample preseparation. The serine monomer is successfully detected as protonated molecules, giving a peak at m/z 106, which is confirmed by the MS/MS fragments. Protonated serine octamer(m/z 841) is also observed with significant abundance in the MS spectra and is confirmed by the MS/MS data, which shows the formation of the serine octamer by a synthesized serine in the resultant mixture. It is also found that the serine octamer yielded equivalent abundance in the DESI mass spectra in a wide pH range(pH=1-5), and that existence of ferrous salt and sunshine are essential for the conversion of aspartic acid to serine in the acidic water solution. |