The discovery of stimuli‐responsive high affinity host–guest pairs with potential applications under biologically relevant conditions is a challenging goal. This work reports a high‐affinity 1:1 complex formed between cucurbit[8]uril and a water‐soluble photochromic diarylethene derivative. It was found that, by confining the open isomer within the cavity of the receptor, a redshift in the absorption spectrum and an enhancement of the photocyclization quantum yield from Φ=0.04 to Φ=0.32 were induced. This improvement in the photochemical performance enables quantitative photocyclization with visible light that, together with the near‐infrared light‐induced ring‐opening reaction and the 100‐fold selectivity for the closed isomer, confirms this as an outstanding light‐responsive affinity pair.

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In bi- and trimetallic Pt-bipyridine-acetylide/Ru-bipyridine complexes the intermetallic Pt-Ru distance is approximately 9 è, and complete Pt-->Ru energy transfer is observed with sensitization of the Ru-based luminescence.

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This paper reports the photochemical behaviour of unbridged (1−6) and bridged zirconocenes (7r, 7m), whose substituents differ in both electron-donor and steric properties. The study of the electronic spectra and EPR spin-trapping experiments showed the photogeneration of ligand-and zirconium-centred radicals at wavelengths higher than 350 nm. This feature makes these complexes suitable as photoiniti-

Summary The epithelium of caput and cauda epididymidis of the rat was studied with transmission electron microscopy (TEM) and freeze‐fracture techniques. In thin sections of both zones, the tissue consisted mainly of tall columnar cells (principal cells) with long stereocilia. Clusters of small membrane‐bound vesicles were located in the lumen between or immediately over the stereocilia. Freeze‐fracture replicas also displayed groups of smooth‐surface vesicles in the same location. Membrane‐bound vesicles isolated from the lumen of the rat epididymis were studied by TEM. In thin sections, some of them contained an electron dense material and others looked empty. In addition, the hydrolases: β‐galactosidase, N‐acetyl‐glycosaminidase, α‐mannosidase, aryl‐sulfatase and β‐glucuronidase were detectable in pellets of vesicles treated with Triton X‐100. The results presented here indicate the presence of membrane‐bound vesicles observed by two different methodologies in the rat epididymal fluid and demonstrate five glycosidases in their content.