CuI‐free click: 4‐Dibenzocyclooctynol reacts, in the absence of a CuI catalyst, exceptionally fast with azido‐containing saccharides and amino acids to give stable triazoles. A biotin‐modified derivative is ideally suited for visualizing and tracking glycoconjugates of living cells that are metabolically labeled with azido‐containing monosaccharides (see image).

Kupferfreie Klick‐Chemie: 4‐Dibenzocyclooctinol reagiert auch ohne Kupfer(I)‐Katalysator extrem schnell mit azidsubstituierten Sacchariden und Aminosäuren unter Bildung stabiler Triazole. Ein biotinyliertes Derivat eignete sich ideal, um metabolisch mit azidsubstituierten Monosacchariden markierte Glycokonjugate in lebenden Zellen zu verfolgen (siehe Bild).

The diagnosis of bacterial infections remains a major challenge in medicine. Although numerous contrast agents have been developed to image bacteria, their clinical impact has been minimal because they are unable to detect small numbers of bacteria in vivo, and cannot distinguish infections from other pathologies such as cancer and inflammation. Here, we present a family of contrast agents, termed maltodextrin-based imaging probes (MDPs), which can detect bacteria in vivo with a sensitivity two orders of magnitude higher than previously reported, and can detect bacteria using a bacteria-specific mechanism that is independent of host response and secondary pathologies. MDPs are composed of a fluorescent dye conjugated to maltohexaose, and are rapidly internalized through the bacteria-specific maltodextrin transport pathway, endowing the MDPs with a unique combination of high sensitivity and specificity for bacteria. Here, we show that MDPs selectively accumulate within bacteria at millimolar concentrations, and are a thousand-fold more specific for bacteria than mammalian cells. Furthermore, we demonstrate that MDPs can image as few as 10(5) colony-forming units in vivo and can discriminate between active bacteria and inflammation induced by either lipopolysaccharides or metabolically inactive bacteria.

Quicker and slicker: An efficient metal‐free 1,3‐dipolar cycloaddition of dibenzocyclooctynes with nitrones proceeded with rate constants of up to 39 M−1 s−1, or up to 300 times faster than similar reactions with azides. This strategy is useful for the site‐specific N‐terminal modification of peptides and proteins (see scheme).