Cyanine-Like Boronic Acid-Derived Salicylidenehydrazone Complexes (Cy-BASHY) for Bioimaging Applications.

Boronic acid-derived salicylidenehydrazone complex (BASHY) dyes with a polymethine backbone were designed to yield efficient red-emitting and two-photon absorbing fluorophores that can be used as markers for astrocytes. The dyes are chemically stable in aqueous solution and do not undergo photodecomposition. Their photophysical properties can be electronically fine-tuned and thereby adapted to potentially different imaging situations and requirements.

Cucurbiturils as supramolecular inhibitors of DNA restriction by type II endonucleases.

Cucurbiturils (CB6 and CB7) were shown to inhibit the enzymatically catalyzed restriction of plasmids and linear DNA. This effect can be inverted by supramolecular masking of the macrocycles through competitive complexation with polyamines. These experiments provide supramolecular control of biocatalytic processes.

Highly efficient singlet-singlet energy transfer in light-harvesting [60,70]fullerene-4-amino-1,8-naphthalimide dyads.

New C60 and C70 fullerene dyads formed with 4-amino-1,8-naphthalimide chromophores have been prepared by the Bingel cyclopropanation reaction. The resulting monoadducts were investigated with respect to their fluorescence properties (quantum yields and lifetimes) to unravel the role of the charge-transfer naphthalimide chromophore as a light-absorbing antenna and excited-singlet-state sensitizer of fullerenes. The underlying intramolecular singlet-singlet energy transfer (EnT) process was fully characterized and found to proceed quantitatively (Φ(EnT)≈1) for all dyads. Thus, these conjugates are of considerable interest for applications in which fullerene excited states have to be created and photonic energy loss should be minimized. In polar solvents (tetrahydrofuran and benzonitrile), fluorescence quenching of the fullerene by electron transfer from the ground-state aminonaphthalimide was postulated as an additional path.

Switching properties of a spiropyran-cucurbit[7]uril supramolecular assembly: usefulness of the anchor approach.

A nitrospiropyran, which was modified with a cadaverine-derived anchor, was investigated with respect to its thermally induced isomerizations, hydrolytic stability of the merocyanine form, and photochromic ring closure. The host-guest complexation of the anchor by the cucurbit[7]uril macrocycle, evidenced by absorption titration, NMR spectroscopy, and electrospray ionization mass spectrometry, produced significant improvements of the switching properties of the photochrome: 1) appearance of the merocyanine form about 70 times faster, 2) practically unlimited hydrolytic stability of the merocyanine (two and a half days without any measureable decay), and 3) fast, clean, and fatigue-resistant photoinduced ring closure back to the spiro form. The importance of an adequate molecular design of the anchor was demonstrated by including control experiments with spiropyrans with a shorter linker or without such structural asset.

Site-selective installation of BASHY fluorescent dyes to Annexin V for targeted detection of apoptotic cells.

Fluorophores are indispensable for imaging biological processes. We report the design and synthesis of azide-tagged boronic acid salicylidenehydrazone (BASHY) dyes and their use for site-selective labelling of Annexin V. The Annexin V-BASHY conjugate maintained function and fluorescence as demonstrated by the targeted detection of apoptotic cells.