КОЛОКВИЈУМ: Др Александар Милосављевић

У оквиру традиционалног колоквијума Института за физику у Београду, у понедељак, 23. априла у 12 часова у сали „Звонко Марић“, др Александар Милосављевић (Синхротон Солеј, Француска) одржаће предавање:


Chasing a non-local energy transfer in a solvated peptide upon X-ray irradiation


Energy transfer processes are highly important in nature and have been attracting large scientific attention. Some examples are Penning ionization, Förster resonance energy transfer, light harvesting etc. In 1997, Cederbaum et al [1] predicted an energy transfer scheme triggered by absorption of energetic electromagnetic radiation, termed intermolecular Coulombic decay (ICD). It has been suggested that the phenomenon is an interatomic decay process, occurring after ionization of an atom in a loosely bound molecular system, in such way that the vacancy is filled by an electron from the neighboring atom through energy transfer, leading to the creation of positively charged atoms or molecules and low energy electrons in the vicinity of the absorber. Since its prediction, ICD has been observed on molecular complexes of various natures. It has been considered to be biologically important [2], and it has been evidenced, for example, in water clusters and solvated organic ions [3,4]. However, ICD has never been observed in a real biological system.

This talk will present experimental technique and some preliminary data on possible observation of non-local energy transfer between a polypeptide and its solvation water molecules. The experimental approach is based on action spectroscopy of trapped ions [5,6]. Doubly protonated ions of substance P, bare and hydrated by 4 and 11 water molecules, have been probed in the oxygen K-edge region using soft X-ray synchrotron radiation and the products of the irradiation were observed by mass spectrometry. Ion yields as a function of the photon energy were obtained and compared to theoretically calculated photoabsorption spectra. The combination of selective excitation by soft X-rays and mass spectrometry-based action spectroscopy, from which ion yields can be extracted for specific fragment ions of the target, allowed us to distinguish effects upon photoabsorption by either the peptide bond or the water cluster attached to the peptide.

[1] L. S. Cederbaum, J. Zobeley, F. Tarantelli, Phys. Rev. Lett. 79, 4778 (1997).
[2] K. Gokhberg, P. Kolorenč, A. I. Kuleff, L. S. Cederbaum, Nature, 505 661 (2014).
[3] T. Jahnke et al., Nat. Phys. 6, 139 (2010).
[4] M. Mucke et al., Nat. Phys. 6, 143 (2010).
[5] A. R. Milosavljević et al., J. Synchrotron Radiat. 19, 174 (2012).
[6] A. R. Milosavljević et al., J. Phys. Chem. Lett. 3, 1191 (2012).