Advanced Photon Source

An Office of Science National User Facility

Microscopy: Research Highlights

Plutonium Tricks Cells by "Pretending" to be Iron

Plutonium Tricks Cells by Pretending to be IronJuly 14, 2011

A new biological pathway by which plutonium finds its way into mammalian cells has been revealed by researchers utilizing the U.S. Department of Energy Office of Science’s Advanced Photon Source at Argonne National Laboratory.

According to the researchers, from Argonne and Northwestern University, the plutonium acts like a "Trojan horse," duping a special membrane protein that is typically responsible for taking up iron.

This discovery may help enhance the safety of workers who deal with plutonium, as well as show the way to new "bio-inspired" approaches for separating radioactive elements from other metals in used nuclear fuel.

Please see: Mark P. Jensen, Drew Gorman-Lewis, Baikuntha Aryal, Tatjana Paunesku, Stefan Vogt, Paul G. Rickert, Soenke Seifert, Barry Lai, Gayle E. Woloschak , and L. Soderholm, “An iron-dependent and transferrin-mediated cellular uptake pathway for plutonium,” Nat. Chem Biol., advance online publication, 26 June, 2011
Zinc availability regulates exit from meiosis in maturing mammalian oocytes

Zinc availability regulates exit from meiosis in maturing mammalian oocytes August 8, 2010

Zinc plays an important role in oocyte maturation, and understanding zinc’s role in oocyte maturation could lead to advances in fertility treatment in future studies. Zinc, copper, and iron are essential components of most cells and there is mounting evidence that cells maintain total concentrations of these metals within a conserved range. However, it has been difficult to determine the concentration and roles of essential metals for rare cells including mammalian oocytes. A team of researchers from Northwestern University and Argonne found that in mouse oocytes the zinc acquired during meiotic maturation—the process by which fertile eggs are formed—is crucial for the late stages of oocyte formation. The study also found that the oocyte’s total zinc content is an order of magnitude larger than its iron or copper content, and it rises even higher at a specific stage of meiotic maturation before decreasing again.

Please see: Kim, A.M., S. Vogt, T.V. O'Halloran and T.K. Woodruff (2010) "Zinc availability regulates exit from meiosis in maturing mammalian oocytes." Nat Chem Biol. 6(9): p. 674-81.
Zernike phase contrast in scanning microscopy

Zernike phase contrast in scanning microscopy September 12, 2010

Scanning X-ray microscopy focuses radiation to a small spot and probes the sample by raster scanning. It allows information to be obtained from secondary signals such as X-ray fluorescence, which yields an elemental mapping of the sample not available in full-field imaging. The analysis and interpretation from these secondary signals can be considerably enhanced if these data are coupled with structural information from transmission imaging. However, absorption often is negligible and phase contrast has not been easily available. Originally introduced with visible light, Zernike phase contrast is a well-established technique in full-field X-ray microscopes for visualization of weakly absorbing samples. On the basis of reciprocity, we demonstrate the implementation of Zernike phase contrast in scanning X-ray microscopy, revealing structural detail simultaneously with hard-X-ray trace-element measurements. The method is straightforward to implement without significant influence on the resolution of the fluorescence images and delivers complementary information. We show images of biological specimens that clearly demonstrate the advantage of correlating morphology with elemental information.

Please see: Holzner, C., M. Feser, S. Vogt, B. Hornberger, S.B. Baines and C. Jacobsen (2010) "Zernike phase contrast in scanning microscopy with X-rays." Nature Physics. 6(11): p. 883-887.