Professor Lindahl's SEE Co / Janis 4K Mossbauer Spectrometer at Texas A&M University
During the summer of 2008, the radiation safety officer at Texas A&M University stopped by my lab in the Chemistry department to inspect the Mossbauer spectrometer that I purchased last year from Janis Research and Science Engineering and Education Co (SEE Co. – formerly Web Research). During our conversation, he mentioned that he had heard that Mossbauer was a “dying technique”. I must say that I found this perception amusing since Mossbauer spectroscopy has recently become our central research tool and is providing us with unprecedented insights into the metabolism of iron in mitochondria and indeed in whole cells. Since our instrument was installed by Dr. Tom Kent in December 2008, we have used it continuously – 24/7. Indeed, its utility has been beyond our expectations such that we now plan to purchase a second instrument. About 2002, I became interested in systems biology – an emerging field
that complements the more traditional biochemical approach of disrupting a cell, purifying a protein, and then studying it using, for example, Mossbauer spectroscopy. Indeed, for the past 20 years, and in collaboration with Dr. Eckard Münck (Carnegie-Mellon University), I have conducted research in this way on the Ni-Fe-S containing enzyme acetyl-CoA synthase/carbon monoxide dehydrogenase. In systems biology, one studies an intact system– in our case the mitochondrion, an organelle often called the “powerhouse” of the cell - in all of its glorious complexity. By applying Mossbauer spectroscopy to an entire organelle, we can see all of the 57Fe in the organelle, and in proportion to the amounts present. Thus, for the first time, we determined the proportion of mitochondrial Fe present as [Fe4S4] clusters, [Fe2S2] clusters, heme Fe, and most interestingly, nonheme mononuclear Fe (see Ref 1). This last species has been especially difficult to track by other methods; but by using |
|
 |
|
Dr. Lindahl and graduate student Ren Miao admiring our Mossbauer instrument. |
|
 |
4.2 K Mossbauer spectra of isolated mitochondria from cells replete (A) and depleted (B and C) in a ferredoxin that is required for Fe/S cluster and heme biosynthesis. In (C), nonheme mononuclear ferrous ions have been oxidized by the O2 in the growth medium, accumulating as aggregated ferric nanoparticles. Figure adapted from ref 2. |
|
Mossbauer spectroscopy, we can observe it and determine its concentration in mitochondria. Mononuclear nonheme Fe plays important roles in cell biology. Once imported into the cell, Fe ions are “earmarked” for different functions and for different compartments of the cell, resulting in bewildering and complex traffic patterns that no one currently understands. Using Mossbauer spectroscopy, we can at least now see these patterns and start to deconvolute them. These targeted nonheme mononuclear Fe ions are used as feedstock for many cellular processes, e.g. heme and Fe/S cluster biosynthesis. Nonheme mononuclear Fe also plays some “bad” roles in cell biology, for example in generating reactive oxygen species that cause mutations in the DNA and contribute to aging. In some diseases, including Friedrich’s Ataxia, X-linked Sideroblastic Anemia with Ataxia, and Parkinson’s disease, nonheme mononuclear Fe accumulates in the mitochondria, exacerbating the symptoms of these diseases.
The spectrum shown reveals aggregated ferric nanoparticles in a sample that mimics one such diseased state. Our future plans are to better understand Fe trafficking in cells and to understand on a mechanistic level why Fe accumulates in these diseased states. In all of these studies, I have no doubt that Mossbauer spectroscopy will play a central role, and I thank both Tom Kent of SEE Co, and Janis Research, for manufacturing these incredible instruments.
References
- “Electron paramagnetic resonance and Mossbauer spectroscopy of intact mitochondria from respiring Saccharomyces cerevisiae” Brandon N. Hudder, Jessica Garber Morales, Audria A. Stubna, Eckard Münck, Michael P. Hendrich, and Paul A. Lindahl, 2007, J. Biol. Inorg. Chem. 12, 1029-1053.
- EPR and Mossbauer Spectroscopy of Intact Mitochondria Isolated from Yah1p-depleted Saccharomyces cerevisiae” Ren Miao, Marlène Martinho, Jessica Garber Morales, Hansoo Kim, E. Ann Ellis, Roland Lill, Michael P. Hendrich, Eckard Münck and Paul A. Lindahl, 2008 Biochemistry, 47, 9888-9899
|
