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Saturday
Jul202013

A New Use for FDG

Hello!

My name is Stephanie Threatt, and I am one of the four summer interns in the Hooker Group this summer. The projects of the summer interns span from computational data analysis of PET images to chemically synthesizing molecules to be used for PET imaging. I’m on the synthetic chemistry side, and lets just say, it can be a challenge.

The basis of my project is to utilize Fluorodeoxyglucose (FDG), which is a commonly used and synthesized radiolabeled molecule that resembles glucose, to eventually label proteins and amino acids. Labeling proteins is currently quite difficult because most radiochemical reactions require very harsh conditions, which would denature the proteins.

My mentor, Changning, and I have basically approached my project with two main steps.  1) Synthesizing fluoromalondialdehyde (FMDA) from FDG via an oxidation reaction and 2) Verifying the ability of FMDA to react and label an amino acid/protein.

I finally figured out the first step of my project a few weeks ago, and this was pretty exciting progress because the reaction method to form FMDA was not only fast but quite simple. I use periodic acid (H5IO6) to oxidize FDG into FMDA, with formic acid and formaldehyde as by products. For the reaction to go to completion, I simply mix FDG and periodic acid in water for 1 minute at room temperature.

Since we were able to confirm the synthesis of FMDA via NMR, we proceeded to the next step of my project. A commonly used research tool for reactions involving heavier, more complex molecules is called Liquid chromatography- Mass spectrometry (LCMS). Using the molecular weight of your product and it’s UV activity, you can determine if your product if being properly formed.

My mentor and I found that the excess periodic acid used to make FMDA was hindering the molecules ability to react with our chosen amino acid, arginine. Therefore, we tried various methods of quenching periodic acid, such as glycol, methanol and even glucose. After several reactions, which were analyzed using LCMS, we were able to determine that glucose successfully quenched periodic acid, rendering it unreactive so that the FMDA-arginine reaction could proceed. Additionally, the need for HCl needed to be evaluated because arginine will only react with FMDA if it is properly protonated.

Determining the appropriate conditions in which to synthesize FMDA and react FMDA with arginine in the presence of formic acid, formaldehyde and periodic acid was quite challenging, but yesterday I collected some very promising data using LCMS. Though I will need to confirm the results by repeating the experiment, I am very hopeful that I may have found good conditions to complete both steps of my project, and if so, I will move to using “hot” 18FDG, which will be really exciting.

I’ll be sure to keep the blog updated with my progress, and thanks for reading! Everyone in the Hooker Group does such fascinating research, so I urge you to keep reading!

 

-Stephanie T.

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