title: Magnesium K-Edge NEXAFS Spectroscopy of Chlorophyll a in Solution.
abstract: The interaction of the central magnesium atom of chlorophyll a (Chl a) with the carbon and nitrogen backbone was investigated by magnesium K near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in fluorescence detection mode. A crude extract of Chl a was measured as a 1 × 10-2mol/L ethanol solution (which represents an upper limit of concentration without aggregation) and as dried droplets. For the first time, the investigation of Mg bound to Chl a in a liquid environment by means of X-ray absorption spectroscopy is demonstrated. A pre-edge feature in the dissolved as well as in dried Chl a NEXFAS spectra has been identified as a characteristic transition originating from Mg in the Chl a molecule. This result is confirmed by theoretical DFT calculations leading to molecular orbitals (MO) which are mainly situated on the magnesium atom and nitrogen and carbon atoms from the pyrrole rings. The description is the first referring to the MO distribution with respect to the central Mg ion of Chl a and the surrounding atoms. On this basis, new approaches for the investigations of dynamic processes of molecules in solution and structure-function relationships of photosynthetic pigments and pigment-protein complexes in their native environment can be developed.
authors: Technische Universität Berlin , Institut für Optik und Atomare Physik, 10623 Berlin, Germany.
authors: Katharina
authors: K
authors: Witte
authors: Physikalisch-Technische Bundesanstalt , 10587 Berlin, Germany.
authors: Cornelia
authors: C
authors: Streeck
authors: Technische Universität Berlin , Institut für Optik und Atomare Physik, 10623 Berlin, Germany.
authors: Ioanna
authors: I
authors: Mantouvalou
authors: Humboldt-Universität zu Berlin , School of Analytical Sciences Adlershof (SALSA), 10099 Berlin, Germany.|Southern Federal University , International Research Center "Smart materials", Rostov-na-Donu 344090, Russia.
authors: Svetlana A
authors: SA
authors: Suchkova
authors: Charles University , Faculty of Mathematics and Physics, Department of Chemical Physics and Optics, 121 16 Prague, Czech Republic.
authors: Heiko
authors: H
authors: Lokstein
authors: Technische Universität Berlin , Institut für Optik und Atomare Physik, 10623 Berlin, Germany.
authors: Daniel
authors: D
authors: Grötzsch
authors: Technische Universität Berlin , Institut für Optik und Atomare Physik, 10623 Berlin, Germany.
authors: Wjatscheslav
authors: W
authors: Martyanov
authors: Physikalisch-Technische Bundesanstalt , 10587 Berlin, Germany.
authors: Jan
authors: J
authors: Weser
authors: Technische Universität Berlin , Institut für Optik und Atomare Physik, 10623 Berlin, Germany.
authors: Birgit
authors: B
authors: Kanngießer
authors: Physikalisch-Technische Bundesanstalt , 10587 Berlin, Germany.
authors: Burkhard
authors: B
authors: Beckhoff
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie Berlin , 12489 Berlin, Germany.
authors: Holger
authors: H
authors: Stiel
mesh_terms: D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D012996:Solutions; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012996:Solutions; D002734:Chlorophyll; C085815:chlorophyll a'; D000431:Ethanol; D008274:Magnesium