Biogeochemistry of Iron, Iodine and Boron in Marine Plant-like Linages: Synchrotron Radiation Methods for Visualizing Chemical State, Localization and Potential Interactions

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With this award the Chemistry of Life Processes Program of the Chemistry Division of NSF are supporting Carl J. Carrano and Frithjof C. Kupper's study of how important trace elements (iron, boron and iodine) are taken up and stored in seaweeds, and how these elements interact with each other so as to affect the plant biology. Seaweeds represent an important resource with a wide range of uses in the food, cosmetic, and fertilizer industries. They are also attracting increasing attention as a source for biofuels that do not compete with terrestrial plants for food production. The project utilizes advanced high resolution synchrotron radiation methods to define the precise locations and chemical states of iron, iodine and boron in two important seaweeds and uses this information to assist in determining the biological importance of interactions between them. This work also provide training for graduate and undergraduate students in a wide range of important techniques. In addition, since San Diego State University has a high minority population (10th largest grantor of minority bachelor's degrees in the USA), this research project is thus expected to favorably impact minority training in the sciences. Outreach activities are also in progress.While in the cytoplasm many metalloproteins are present as a complicated mixture not easily amenable to simple analysis without prior potentially destructive, and certainly disruptive, isolation and purification. Many other metalloproteins are stored, sequestered or localized in discrete locations within the cell/organelles and are also difficult to isolate and study. As the resolution and flux density of synchrotron radiation (SR) increases, it may be possible to pinpoint such systems and analyze and characterize them directly in situ without need for isolation or purification. Thus, one goal of this research is to see what the limits are for SR methods for visualizing the chemical state, localization and potential interactions of trace elements as applied to biological samples given the increasing capabilities of 3rd generation synchrotrons where significant progress (both in terms of brilliance and resolution) has been evident. The project is using utilizing advanced high resolution (micron to submicron) SR methods, i.e. microprobe, 3D tomography, IR/Raman, XANES and EXAFS to define the precise locations and chemical states of iron, iodine and boron in two model marine macroalgae (Ectocarpus siliculosis, Macrocystis pyrifera). The investigators use this information to assist in determining the biological importance of interactions between the elements. Seaweeds represent an important resource with a wide range of uses in the food, cosmetic, and fertilizer industries. They are also attracting increasing attention as a source for biofuels that do not compete with terrestrial plants for food production.