Fig. 2. Biodistribution data for ⁶⁸Ga-labeled peptide trimers, 90 min p.i.. a, Cartoon as aidé-memoire for the placement of tyrosines (symbolized by “O” letters, indicating that exchange of a Phe by a Tyr essentially translates to insertion of a single oxygen atom into the para-C–H bond of the aromatic ring); octanol–water (pH 7.4) distribution coefficients of the ⁶⁸Ga labeled compounds (determined by shake-flask method using n-octanol as organic and PBS as aqueous phase, mean ± SD rounded to one decimal place, n = 8); and RP-HPLC retention times of the non-radioactive ^natGa³⁺ complexes. b, Biodistribution in selected organs and tissues. Saturated bars indicate injected molar amounts of approx. 100 pmol (mean ± SD, n = 5); respective adjacent shaded bars of the same color show blockade (50 nmol unlabeled, administered 10 min before the radioactive compound, mean ± SD, n = 3). c, Tumor-to-organ ratios derived from biodistribution data (mean ± SD, n = 5). Numerical data for graphs shown in b and c, including the exact values of injected amounts, are provided in the ESI,† Tables S1–S10.