Interdisciplinary Life Science - PULSe Great research is a matter of choice

Yulia Pushkar

Yulia Pushkar Profile Picture

Assistant Professor - Physics
M.S., Moscow State University, Russia 1999; Ph.D., Free University Berlin, Germany 2003

Contact Info:

Training Group(s):
Biomolecular Structure and Biophysics

Current Research Interests:

Energy Research:

Sunlight provides by far the largest of all carbon-neutral energy sources. More energy from sunlight strikes the Earth in one hour (4.3 × 1020J) than all the energy consumed on the planet in a year (4.1 × 1020J). In nature, Photosynthesis accomplishes the task of light harvesting and its conversion into chemical energy. This process is extremely complex and requires interplay of many proteins and protein complexes. The direct conversion of visible light to chemical energy (fuel) by a synthetic device made of inorganic, organic or hybrid materials is an attractive method for harvesting sunlight in the form of fuel. Different conceptual schemes have been proposed in which sunlight is used to drive the flow of electrons and protons. Coupling the electrons and protons to catalysts breaks the bonds of water and makes the bonds of H2 and O2 to effect solar fuel production. This process requires efficient and robust water oxidation catalysts that can be incorporated into a molecular assembly or other microscopic structures or immobilized on an electrode surface.

Metals in the Brain:

Very recently, the importance of heavier metals, such as Fe, Cu, Mn, Zn, (0.1-0.5 mM concentrations in gray matter) for brain function was recognized. The brain utilizes these metal ions in many biochemical processes, including signalling (Cu and Zn). Abnormalities arise by two mechanisms: i) metal ion-mediated protein aggregation, ii) metal-catalyzed oxidative reactions. Proteins with redox-active metal ions have highly structured and selective active sites which prevent inappropriate electron transfer. Redox-active metals are chaperoned in the cell to prevent oxidative side reactions. It is common for neurodegenerative diseases that the binding of metal ions in the brain is highly affected. Pathological formations with increased metal concentrations were observed in brain tissues of patients with Alzheimer's and Parkinson's diseases.

We use high resolution (micro to nano) X-ray imaging for simultaneous detection of metals (such as Fe, Cu, Mn, Zn) in neuron cell cultures and brain tissues. Subsequent collection of XAS spectra from selected areas on a sample will provide information about the redox state and ligation of the metals. There are several advantages of the proposed technique: i) it does not require staining, thus samples are unaltered prior to analysis ii) it detects all metal ions, as compared with fluorescent probes whose limited affinities result in primarily "free" ion detection; iii) it probes the redox state and the coordination environment of the metal; iv) if applied in parallel with conventional microscopy, it identifies the location of areas with increased metal concentration with respect to the tissue structure. This will result in detailed structural and functional information on metal-binding sites in normal (functional) and abnormal metalloprotein assemblies relevant for brain function. Information about the function of metals in the brain and their involvement in the development of neurodegenerative diseases will aid in the design of therapies.

Selected Publications:

Visible Light-Induced Electron Transfer from Di-µ-oxo-Bridged Dinuclear Mn Complexes to Cr Centers in Silica Nanopores Walter Weare, Yulia Pushkar, Vittal Yachandra, Heinz Frei, Journal of American Chemical Society 2008.

"Structural changes in the Mn4Ca cluster and the mechanism of photosynthetic water splitting" Yulia Pushkar, Junko Yano, Kenneth Sauer, Alain Boussac, Vittal Yachandra Proceedings of the National Academy of Science 2008, V. 105, N. 6, 1879-1884.

"Structure and orientation of the Mn4Ca cluster in plant Photosystem II membranes studied by polarized range-extended X-ray absorption spectroscopy" Yulia Pushkar, Junko Yano, Pieter Glatzel, Johannes Messinger, Azul Lewis, Kenneth Sauer, Uwe Bergmann, Vittal K. Yachandra Journal of Biological Chemistry 2007, V. 282, N. 10, 7198-7208.

"Where Water is Oxidized to Oxygen: Structure of the Photosynthetic Mn4Ca Cluster" Junko Yano, Jan Kern, Kenneth Sauer, Matthew J. Latimer, Yulia Pushkar, Jacek Biesiadka, Bernhard Loll, Wolfram Saenger, Johannes Messinger, Athina Zouni, Vittal K. Yachandra Science 2006, V.314; 821-825.

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