Spectral properties of ionic benzotristhiazole based donor-acceptor NLO-phores in polymer matrices and their one- and two-photon cellular imaging ability.

A series of ionic benzotristhiazolium (BTT) push-pull chromophores, with different nitrogen donor groups and different lengths of conjugated bridges, was successfully doped in polar polymer matrices (PVC and PSS). The spectral (photophysical) properties of their low concentration thin polymeric films are compared with those in solution and are discussed in terms of matrix polarity/viscosity influence, specific polymer-chromophore interaction, structure-spectral property relationship and Twisted Intramolecular Charge-Transfer (TICT) state formation. The elimination of a non-emissive phantom and TICT state formation by restricted intramolecular rotations in the polymer matrix or viscous solvent results in a relatively high ΦF of all the investigated NLO-phores; particularly for near-infrared NIR molecular rotors bearing diphenylamino and julolidine donor groups. Because of cationic characteristics, small molecular weight, calculated high second hyperpolarizability and significant emission efficiency dependence on surroundings' viscosity (rigidochromic effect), two dyes were chosen as candidates for potential fluorescent probes for one-photon (1P) and two photon (2P) cellular imaging. The selected BTT NLO-phore with a julolidine donor is promising as a mitochondria-specific fluorescent small molecular probe for live cell super-resolution imaging with low cytotoxicity and good photostability, and is also potentially suitable for super-resolution STED imaging.

Isatin phenylhydrazones: anion enhanced photochromic behaviour.

The photochemical properties of two basic easily synthesized isatin N(2)-phenylhydrazones were investigated. Contrary to the corresponding isatin N(2)-diphenylhydrazones, only Z-isomers were isolated from the reaction mixtures during the synthesis due to their stabilization by intramolecular hydrogen bonding. Although the presence of the C=N double bond creates conditions for the formation of a simple on-off photoswitch, the low photochemical quantum yield and particularly the low switching amplitude in absorbance hamper their photochromic applications. However, the addition of strongly basic anions to phenylhydrazone solutions leads to isatin NH group deprotonation and creates a new diazene T-type Vis-Vis photochromic system with sufficiently separated absorption maxima. Interestingly, although the thermally stable A-form is also photostable in ambient light, its irradiation with a stronger LED source leads to thermally unstable B-form formation which rapidly isomerizes back to the corresponding A-form. The process is reversible and switching cycles can be repeated in both directions. The important advantages of this two-component organic chromophore-inorganic anion photochromic system are its easy synthesis, easy handling due to its insensitivity to room light, easy further structural modification and reversibility. The corresponding photochemical quantum yield, however, remains relatively low (Φ âˆ¼ 0.001). The theoretically calculated properties are in agreement with the obtained experimental results and support the proposed reaction mechanism.

Expression of the two maize TATA binding protein genes and function of the encoded TBP proteins by complementation in yeast.

A single gene encodes the TATA binding protein (TBP) in yeasts and animals. Although two TBP-encoding genes (Tbp) previously were isolated from both Arabidopsis and maize, the expression and in vivo function of the encoded plant TBPs were not investigated. Here, we report that the two highly conserved maize Tbp genes are unlinked and reside within larger, ancestrally duplicated segments in the genome. We find quantitative differences in Tbp1 versus Tbp2 transcript accumulation in some maize tissues. These nonidentical expression patterns may indicate differences in the tissue-specific regulation of these genes, which might allow the two encoded maize TBP isoforms to perform nonoverlapping functions in the plant. In addition, we show that the maize TBP products, unlike animal TBPs, are functionally interchangeable with yeast TBP for conferring yeast cell viability. This is a conclusive demonstration of in vivo activity for a nonyeast TBP protein, and these complementation results point to particular amino acids in TBP that are likely to influence species-specific protein interactions.