In this issue, S. H. Liang et al. review chemistry for positron emission tomography (PET). What are recent advances in ¹¹C-, ¹⁸F-, ¹³N-, and ¹⁵O-labeling reactions? Minireviews deal with photosensitizer strategies for smarter photodynamic therapy beacons (G. Zheng et al.) and multimodality imaging agents with PET as the fundamental pillar (W. Cai et al.).

In the Communications section, Y. Teki et al. investigate the excited-state dynamics of a photostable luminescent organic radical doped in a host crystal (see picture). R. P. Lively et al. present molecularly mixed composite membranes for advanced separation processes. D. Romo et al. describe the total synthesis and anticancer activity of (+)-hypercalin C and congeners, and O. P. Varghese et al. discovered an unexpected role of hyaluronic acid in trafficking siRNA across the cellular barrier, and developed a biomimetic, anionic, non-viral transfection method.

• Angewandte Chemie 9/2019: The Fundamental Pillar,
  Angew. Chem. Int. Ed. 2019, 58 (9).