Solid state radiolysis of non-proteinaceous amino acids in vacuum: astrochemical implications

Stability toward High Energy Radiation of Non-Proteinogenic Amino Acids: Implications for the Origins of Life

“…From three measurements of melting enthalpy the average residual purity of the radiolyzed α-AIB has been re-calculated and reported in Table 1 . In the previous work [ 36 ], the DSC traces of α-AIB pristine and radiolyzed were characterized by an extremely broad transition which has affected both the melting point peak position and the melting enthalpy leading to unreliable conclusions which are superseded by the present work.…”

“…About amino acids radiolysis, there are available also the very important and classical works of Bonner and colleagues [ 21 , 56 , 57 , 58 , 59 , 60 ], which were specifically designed to test the Wester-Ulbricht hypothesis that parity violation in the β-decay may have originated the enantiomeric excess in the biochemical world, and the work of Kminek and Bada [ 61 ]. However, with the exclusion of Cataldo and colleagues [ 30 , 32 , 33 , 34 , 35 , 36 ], no systematic studies on the effects of high energy radiation on amino acids have been made. This paper represents a continuation of the work.…”

“…In the previous preliminary work [ 36 ] the purity of the radiolyzed amino acids was determined through Equation (1), but the measurements were made in conventional aluminum crucibles with punched cap. However, since most of the amino acids studied melt above 300 °C (see Table 2 ), the measurement of the melting enthalpy was affected by a parallel thermo-oxidative degradation of a given amino acid.…”

“…As reference, the same measurement was also made on standard pristine amino acid dissolved in the same medium at the same concentration. From the ratio of the average specific optical rotation after radiolysis [a]γ and before radiolysis [a] 0 the residual optical activity Rγ was determined [ 32 , 33 , 34 , 35 , 36 ]: Rγ% = 100{[α] γ /[α] 0 } …”

“…As discussed previously, only 10% of the total amino acid species found in meteorites are proteinogenic [ 7 , 11 , 14 ]. We thus decided to irradiate in the solid state to 3.2 MGy a series of unusual amino acids belonging to the classes found in carbonaceous chondrites; the preliminary results were published elsewhere [ 36 ], while the present work represents a full account of our results. The present work is part of our long-term research project on chirality in terms of chiral polymer synthesis, chiral induction, and amplification [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ].…”