Two-photon uncaging: New prospects in neuroscience and cellular biology.

An uncaging process refers to a fast and efficient release of a biomolecule after photochemical excitation from a photoactivatable precursor. Two-photon excitation produces excited states identical to standard UV excitation while overcoming major limitations when dealing with biological materials, like spatial resolution, tissue penetration and toxicity and has therefore been applied to the uncaging of different biological effectors. A literature survey of two-photon uncaging of biomolecules is described in this article, including applications in cellular- and neurobiology.

A liquid crystalline supramolecular complex of C60 with a cyclotriveratrylene derivative

Cyclotriveratrylene (CTV) derivatives substituted with 9 (1) or 18 (2) long alkyl chains have been prepared. Whereas no liquid crystalline behavior has been observed for 1, the CTV derivative 2 has mesomorphic properties. Indeed, at room temperature compound 2 exhibits a nematic phase characterized by cybotactic groups with a local lamello-columnar order. Both CTV derivatives 1 and 2 are able to form supramolecular complexes with C60 in the solid state. In both cases, the 2:1 host-guest species have been obtained as brown compounds. No liquid crystalline behavior was observed for the supramolecular complex [C60 is included in (1)2]. In contrast, observation of the brown product obtained from C60 and the CTV derivative 2 directly after preparation by polarized optical microscopy revealed a fluid birefringent phase at room temperature. When the sample is heated above 70 degrees C, the birefringence of the texture under the microscope disappears and the X-ray diffraction pattern is transformed into a pattern characteristic of a cubic phase. For the first time in thermotropic liquid crystals, the space group of this cubic phase can be assigned as I4(1)32.

Sodium 5-nitro-2-pyridonate trihydrate

The title compound, alternatively sodium pyridin-2-olate trihydrate, Na(+).C(5)H(3)N(2)O(3)(-).3H(2)O, crystallizes in the P-1 space group. It is made up of edge-shared chains of NaO(6) octahedra with five water molecules and one 5-nitro-2-pyridonate anion. Four of these water molecules are bicoordinating, involved in connecting the adjacent octahedra, and the fifth is coordinated to only one octahedron. The crystal structure is stabilized by a network of strong O-H.O and O-H.N interactions. The organic moieties occupy the space between the chains with an antiparallel alignment.

Benzyltriphenylphosphonium glutaconaldehyde

The title compound, C(25)H(22)P(+).C(5)H(5)O(2)(-), crystallizes in space group P2(1)/c. The phosphonium cations form zigzag chains with P.P distances of 6.475 (1) and 8.287 (2) A, and are related by inversion centres. Two types of attractive edge-to-face phenyl interactions exist, resulting in a dominant supramolecular motif. The glutaconaldehyde anions occupy the interchain spacing and hold adjacent chains together via multiple C-H.O hydrogen bonds. The bond-length alternation, a parameter which reveals the non-linear optical efficiency at the molecular level, is optimized in the chromophore anion.

Investigations of Thin Films with Amphiphilic Dendrimers Bearing Peripheral Fullerene Subunits.

In spite of a molecular mass of 7704.6 g mol(-1), third-generation compound G3 (shown schematically; Z=C(8)H(17)) is able to form stable Langmuir films. In a systematic study, the amphiphilic properties of the corresponding dendrimers of first (G1) and second generation (G2), with one and two peripheral fullerene units, respectively, were investigated and a model could be proposed for the multilayer films obtained from G1.

A Copper(I) Bis-phenanthroline Complex Buried in Fullerene-Functionalized Dendritic Black Boxes.

Virtual inaccessibility to external contact was revealed by electrochemical investigations for a bis(1,10-phenanthroline)copper(I) core embedded in dendrimers with up to 16 peripheral fullerene units (shown schematically). With increasing numbers of fullerene units, less and less light is available to the core, and the small quantity of light energy that reaches the central Cu(I) complex is returned to the external fullerenes by energy transfer-the central core is buried in a dendritic black box.