Speaker
Description
In a series of combined experimental studies and molecular dynamics simulations on linear and cyclic dipeptides in gas phase we identified pathways that may provide effective mechanisms for their survival to temperature variation or exposition to radiation in space [1]. The most intriguing result is that these molecules may either ‘protect’ themselves turning the linear structure into a cyclic one by the formation of an intramolecular peptide bond or release reactive neutral/charged fragments which may act as seeds to re-form the dipeptide or even longer linear peptide chains. To investigate these mechanisms when the molecules are embedded in an environment, we studied the irradiation of homogeneous films of selected biomolecules (Alanine, Linear and Cyclo AlaAla, Linear and Cyclo GlyPhe and Cyclo GlyGly) by 12C4+ beams of 0.98 meV/u at 10, 80 and 300 K using infrared spectroscopy (IR) at the IRRSUD beamline of GANIL (Caen, France). DFT calculations are used to assign the IR spectra, to rule out unstable conformers, and to identify relevant features for further analysis.
The most interesting results obtained are:
-the apparent destruction cross section indicates that at room temperature the cyclo species are more resistant than the linear ones and the radioresistance of both species is not affected by the temperature in the studied range;
- the variation of the intensity of IR bands as a function of the ion fluence for both Alanine aminoacid and linear AlaAla dipeptide depends on the selected band. In the case of Alanine the observation of a high similarity between the experimental spectra of monomeric alanine after irradiation and linear AlaAla before irradiation lead to the hypothesis that under irradiation alanine undergoes a “polymerization”, thus forming a linear dipeptide. Similarly the variation of the IR spectra of the linear AlaAla has been attributed to the elongation of the linear chain leading to the formation of a linear AlaAlaAlaAla by comparison with simulations.
Acknowledgement. COST action CA20129 - Multiscale Irradiation and Chemistry Driven Processes and Related Technologies (MultIChem); Italy-Sweden MARB project (PGR02090) of MAECI; ICSC-Centro Nazionale di Ricerca in High Performance Computing, Big Data and Quantum Computing, funded by European Union-NextGenerationEU (grant CN00000013).
