Drs. Andreason and Shoaf are interested in using PET to study the use of alpha-(11C-methyl)-L-tryptophan as a tracer of brain serotonin synthesis. The rate of accumulation of radioactivity of this tracer as measured by PET is assumed to be indicative of the rate of serotonin synthesis and may be correlated with increased aggressive/impulsive behavior of patients. The objective of this project is to synthesize alpha-methyl-L-tryptophan labeled with carbon-11, a cyclotron produced, positron-emitting radionuclide, which will permit imaging the brain using positron emission tomography (PET). In order to use this tracer for serotonin synthesis, it is first necessary to establish the pharmacokinetic parameters of the tracer. Also, in order to relate the accumulation of the tracer to the rate of serotonin synthesis, the difference in the enzyme kinetics of the tracer and serotonin must be determined. I was not able to obtain alpha-methyl-L-tryptophan commercially. I developed a HPLC procedure for the resolution of the racemate into it enantiomers using a cyclodextrin column. The method provided the L-form in ammonium acetate solution. However, enzyme kinetics requires the L- form free of ammonium acetate. Attempts are being made to obtain the L- form free of ammonium salts.
