Fluorination at the 4 position alters the substrate behavior of L-glutamine and L-glutamate: Implications for positron emission tomography of neoplasias. - Jeitner TM; Kristoferson E; Azcona JA; Pinto JT; Stalnecker C; Erickson JW; Kung HF; Li J; Ploessl K; Cooper AJL (Journal of fluorine chemistry, 2016)