Gas Phase Photoemission Beamline CORE LEVEL SPECTROSCOPY AND
Gas Phase Photoemission Beamline CORE LEVEL SPECTROSCOPY AND TAUTOMERISM OF KEY BIOMOLECULES IN THE GAS PHASE Vitaliy Feyer Sincrotrone Trieste, Italy OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Tautomerism of free molecules in photoemission - Tautomerism is the ability of a molecule to exist in more than one chemical form. - Many tautomers are formed by migration of a hydrogen atom, accompanied by a switch of a single bond and neighboring double bond. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Biomolecular Building Blocks OSU Symposium, June, 2010
Gas Phase Photoemission Beamline • “Building blocks” interaction Normal base pairing in DNA is A-T and G-C. The tautomers forms are capable of unusual base pairing like T-G and C-A. Tautomers can cause genetic mutations by pairing incorrectly with complementary bases. Mutations are the precursors to many molecular-based diseases, including cancer. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Environment !!! Study them in the GAS PHASE !!! Quantitative techniques !!!
Gas Phase Photoemission Beamline Gas Phase beamline characteristic: 36 period, 12. 5 cm period undulator. Padmore type monochromator (variable angle spherical grating). Resolution: 2 me. V @ 64 e. V, with high flux easily and reproducibly achieved. < 40 me. V @ 400 e. V < 50 me. V @ 530 e. V < 80 me. V @ 860 e. V. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Core level photoemission Photoelectric effect: hv=EB+EK Advantages: - chemical shifts; - well above threshold, cross-sections of core electrons are equal, so the peak intensities (areas) directly reflect population; - thermal equilibrium. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Conformational/tautomeric investigation of 2 -mercaptopyridine C-S-H S 2 p C=S Core level photoemission spectroscopy Quantitative techniques: population of C-S-H : C=S can be directly extracted from spectra, Free jet microwave spectroscopy (Walther Caminati group) High resolution: three forms SHs, SHa and C=S are observed SHs Population (%) G/k. J·mol-1 OSU Symposium, June, 2010 95. 5 1 XPS (339 K) MW (403 K) 89 5 XPS (339 K) MW (403 K) SHa 8 2 0. 0 8. 1 C=S 4. 5 1 3 1 8. 6 11. 4
Gas Phase Photoemission Beamline Cytosine tautomers R. D. Brown, et al, J. Am. Chem. Soc. 111, 1989, 308. (microwave spectroscopy ) 2 b and 1, 3. E. D. Radchenko, et al, J. Mol. Struct. 116, 1984, 387. M. Szczesniak, et al J. Am. Chem. Soc. 110, 1988, 8319. (matrix isolation infrared studies) 1 and 2 b G. Fogarasi, J. Phys. Chem. A. 106, 2002, 1381. S. A. Trygubenko, et al Phys. Chem. Phys. 4, 2002, 4192. (theoretical calculation) 2 b, 2 a, 1, and 3 Can XPS photoemission directly give us information about populations of cytosine tautomers in the gas phase? OSU Symposium, June, 2010
Gas Phase Photoemission Beamline X-ray Photoemission Spectroscopy Advantages of XPS: Enol forms Keto forms 3 and 1 -thermal equilibrium -well above threshold cross-sections of 1 s electron are equal, so the peak area directly reflect population Experiment: T 1 26 % (T 2 a + T 2 b) 63 % T 3 11 % OSU Symposium, June, 2010 Theory: T 1 32. 8 % T 2 a 17. 7 % T 2 b 34. 4 % T 3 15 %
Gas Phase Photoemission Beamline O 1 s XPS Keto and enol tautomeric forms of cytosine and guanine sufficiently populated under present experiment conditions For uracil and thymine only keto form is observed. O. Plekan et al. Chem. Phys. 347, 2008, 360. J. Phys. Chem. A. 113, 2009, 9376. V. Feyer et al. J. Phys. Chem. A. 113, 2009, 5736. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Conclusions…. • Tautomers of molecules have been clearly resolved in photoemission spectra and their relative populations have been determined. • Photoemission can be used as complementary technique to study the shape of molecules. • The gas-phase experimental data serve as benchmarks for quantum chemical calculations. Perspectives… The study of biomolecules will benefit from the high flux of the Free Electron Laser FERMI at ELETTRA. OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Free Electron Laser FERMI@ELETTRA Low-Density Matter beamline under construction (free electron laser facilities ) Elettra LDM team: Carlo Callegari – coordinator Angelica Moise – postdoc Vitaliy Feyer – postdoc Machine parameters FEL-1 FEL-2 Photon energy 12 -62 e. V 62 -413 e. V Pulse length 30 -100 fs < 100 fs Repetition Rate 10 -50 Hz photon/ pulse 1014 1013 OSU Symposium, June, 2010
Gas Phase Photoemission Beamline Future experiments Helium nanodroplets machine is being constructed at the University of Freiburg (Prof. F. Stienkemeier in collaboration with partners) Photo electron spectroscopy of molecules in liquid helium droplets (small molecules, biomolecules, organic nanostructures, organic semiconductors) fs pump-probe studies (IR/UV –XUV) - relaxation mechanism in superfluid helium, - charge transfer in heterogeneous structures. Imaging of gas-phase clusters and nanoparticles Low-Density Matter beamline will be opened for users in 2011 !!! OSU Symposium, June, 2010
Gas Phase Photoemission Beamline I would like to thank… Oksana Plekan Robert Richter Marcello Coreno Monica de Simone Kevin Prince Gas Phase Photoemission Beamline at Elettra, Trieste, Italy B. M. Giuliano, S. Melandri, L. Evangelisti, A. Maris, W. Caminati Chemistry department, University of Bologna, Italy V. Carravetta Institute of Chemical Physical Processes, Pisa, Italy A. B. Trofimov I. L. Zaytseva Irkutsk State University, Irkutsk, Russian Federation E. V. Gromov J. Schirmer Theoretische Chemie, Physikalisch. Chemisches Institut, Heidelberg, Germany …and thanks a lot for your attention… OSU Symposium, June, 2010
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