Metabolic Imaging: Watching Sugars Move in Plants

Sucrose is one of the main dietary sugars and the starting point for many biochemical processes.

The Science

Fluorine-18 is a radioactive isotope that emits positrons. Using positron emission tomography (PET), scientists can image the movement and localization, in living organisms, of molecules that contain fluorine-18. Fluorine-18-labeled-fluorosugars, that is, natural sugars into which fluorine-18 atoms have been incorporated, enable study of the mechanisms by which living organisms use and process these biomolecules and offer opportunities to observe sugar distribution and metabolism in real time. Fluorine-18 fluoro-deoxyglucose (FDG) has already been established as an important PET imaging agent in human medicine. It is well known that vascular plants transport the bulk of their carbohydrate load in the form of sucrose. Now, U.S. Department of Energy scientists at the University of Missouri–Columbia have synthesized fluorine-18-fluoro-deoxy-sucrose (FDS) and used it to obtain the first images of corn plant leaves that demonstrate realtime transport of the sugar. This procedure has the advantages of high yield and short reaction times for the final two steps. Their results will enable investigators to image sucrose metabolism in living plants and, from these images, gain insight into metabolic pathways in plants with potential value for biofuel production.

Summary

Fluorinated sucrose derivatives and fluorinated carbohydrates in general have been of interest for some time. Fluorinated carbohydrates are important in understanding the role of carbohydrate metabolism in both plants and animals. Generally, a fluorinated carbohydrate is prepared by replacement of one of the hydroxyl groups on the carbohydrate with a fluorine atom. Such a substitution removes the possibility of that position serving as a hydrogen-bond donor, but not as a hydrogen bond acceptor. Hence, biochemical differences may exist in the behavior of the fluorinated vis-à-vis a native carbohydrate.

Principal Investigator

Vikram Gaddam
University of Missouri–Columbia

Co-Principal Investigator

Michael Harmata
University of Missouri–Columbia

References

Gaddam, V., and M. Harmata. 2013. “Synthesis of 6′-Deoxy-6′-Fluorosucrose,” Carbohydrate Research 369, 38–41. DOI:10.1016/j.carres.2012.12.001.