By replacing the carboxylate group of amino acids with a trifluoroborate group, a multinational research team has created boramino acids. The researchers led by Zhibo Liu and Xiaoyuan Chen of NIH’s National Institute of Biomedical Imaging & Bioengineering say the new compounds, when labeled with 18F, could serve as positron emission tomography imaging probes to track amino acid transporter protein activity in cells and help guide disease diagnosis and drug development (Sci. Adv. 2015, 10.1126/sciadv.1500694). Amino acid transporters are membrane proteins that facilitate cellular uptake of nutrients and neurotransmitters. Abnormal expression of these proteins is associated with cancer, addiction, and mental diseases. Studying the in vivo expression of the proteins has been hampered, however, by lack of appropriate tracers. Knowing that other scientists had developed 18F-labeled sugars for PET imaging and had tried substituting amino acid carboxylate groups with boronic acid, Liu, Chen, and their coworkers reasoned that incorporating BF3 into amino acids might impart just the properties they needed. The team has found that boramino acids and amino acids are “indistinguishable twins” to amino acid transporters. The researchers demonstrated the boramino acids’ worth by obtaining high-contrast PET images of tumor-bearing mice.