We report a new two-photon fluorescence turn-on probe 6-[(E)-3-oxo-1-dodecenyl]-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (CL2) that is designed specifically for visualizing lipid rafts in living cells and tissues. This probe emits much brighter two-photon excited fluorescence in lipid rafts than in non-raft domains and allows direct visualization of the lipid rafts in the live cells and pyramidal neuron layer of the CA1 region at a depth of 100-250 mum in live tissues using two-photon microscopy.

The living image: The efficient two‐photon probes AZn1 and AZn2 (see picture for rat brain tissue) show 24‐ to 52‐fold two‐photon excited fluorescence enhancement in response to Zn2+. They can selectively detect intracellular free Zn2+ ions in live cells and in living tissues at a depth of 80–150 μm without interference from other metal ions and the membrane‐bound probes.

Move with the groove: Two‐photon fluorescent pH probes and a two‐photon lysotracker (AL1) can visualize acidic vesicles in live cells and living tissue for a long period of time without mistargeting and photobleaching problems. Using AL1, vesicles can be tracked in real time (see picture).

Auf Schritt und Tritt verfolgt: Durch Zweiphotonenmikroskopie mit pH‐Fluoreszenzsonden und einem „Lysotracker“ (AL1) gelingt es, saure Vesikel in lebenden Zellen und lebendem Gewebe über lange Zeiträume sichtbar zu machen; Probleme durch Fehlmarkierungen und photochemische Zerstörung treten dabei nicht auf. Mithilfe von AL1 lassen sich die Vesikel in Echtzeit verfolgen (siehe Bild).