Characterisation of bifunctional ruthenium(ii) complexes, potential DNA photo-probes. Presence of folded and unfolded conformers

Novel bifunctional ruthenium(n) complexes, [Ru(TAP)2(POQ-Nmet)]2+ and [Ru(BPY)2(POQ-Nmet)]2+(la, 2a), containing a metallic and an organic moiety, have been prepared as photoprobes and photoreagents of DNA(TAP = 1,4,5,8-tetraazaphenanthrene, POQ-Nmet = 5-[6-(7-chloroquinolin-4-yl)-3-thia-6-azaheptanamido]-l,10phenanthroline). The ES mass spectrometry and 'H NMR data in organic solvents indicate that the quinoline moiety exists in both the protonated and non-protonated form. Moreover, the comparison of the NMR data with those of the corresponding monofunctional complexes(without quinoline) evidences that [Ru(TAP).2(POQ-Nmet)]2+ and [Ru(BPY)J(POQ-Nmet)]2+ are unfolded when the quinoline unit is protonated whereas deprotonation permits folding of the molecule. In the folded state the spatial proximity of the electron donor(the organic moiety) and electron acceptor(the metallic moiety) in [Ru(TAP)2(POQ-Nmet)]2+ favours intramolecular photo-induced electron transfer, which has been shown in a previous study to be responsible for the very low luminescence of la in non-protonating solutions. The restoration of the luminescence by protonation of the quinoline moiety as observed previously is in agreement with the unfolding of the molecule demonstrated in this work. The existence of such folding-unfolding processes related to protonation is crucial for studies of la with DNA. © The Royal Society of Chemistry 2000.

A new bifunctional para-toluenesulfonamidophenanthroline-aminoquinoline ligand. Synthesis and characterisation of the corresponding Ru(II) complex

The synthesis and characterisation of a new bifunctional Ru(II) complex are presented. This compound contains a metallic unit, photo-reactive versus the guanines of DNA, and a new bifunctional ligand. An intramolecular luminescence quenching makes this complex an attractive candidate for photoprobing DNA where the intramolecular quenching process is inhibited with restoration of luminescence. © 1998 Elsevier Science S.A. All rights reserved.

Study of gene expression in thyrotropin-stimulated thyroid cells by cDNA expression array: ID3 transcription modulating factor as an early response protein and tumor marker in thyroid carcinomas.

Induction of cell proliferation by mitogen or growth factor stimulation leads to the specific induction or repression of a large number of genes. To identify genes differentially regulated by the cAMP-dependent transduction pathway, which is poorly characterized so far, we used the cDNA expression array technology. Hybridizations of Atlas human cDNA expression arrays with (32)P-labeled cDNA probes derived from control or thyrotropin (TSH)-stimulated dog thyrocytes in primary culture generated expression profiles of hundreds of genes simultaneously. Among the genes that displayed modified expression, we selected the transcription factor ID3, whose expression was increased by a cAMP-dependent stimulus. ID3 overexpression after TSH stimulation was first verified by Northern blotting analysis, and its mRNA regulation was then investigated in response to a variety of agents acting on thyrocyte proliferation and/or differentiation. We show that: (1) ID3 mRNA induction was stronger after stimulation of the cAMP cascade, but was not restricted to this signaling pathway, as phorbol myristate ester (TPA) and insulin also stimulated mRNA accumulation; (2) in contrast, powerful mitogens for thyroid cells, epidermal growth factor and hepatocyte growth factor, did not significantly modify ID3 mRNA levels; (3) ID3 protein levels closely parallelled mRNA levels, as revealed by immunofluorescence experiments showing a nuclear signal regulated by TSH; (4) in papillary thyroid carcinomas, ID3 mRNA was downregulated. Our results suggest that ID3 expression might be more related to the differentiating process induced by TSH than to the proliferative action of this hormone.

Supercontinuum Generation by Stimulated Raman Scattering and Parametric Four-Wave Mixing in Photonic Crystal Fibers

Supercontinuum generation is investigated experimentally and numerically in a highly nonlinear indexguiding photonic crystal optical fiber in a regime in which self-phase modulation of the pump wave makes a negligible contribution to spectral broadening. An ultrabroadband octave-spanning white-light continuum is generated with 60-ps pump pulses of subkilowatt peak power. The primary mechanism of spectral broadening is identified as the combined action of stimulated Raman scattering and parametric four-wave mixing. The observation of a strong anti-Stokes Raman component reveals the importance of the coupling between stimulated Raman scattering and parametric four-wave mixing in highly nonlinear photonic crystal fibers and also indicates that non-phase-matched processes contribute to the continuum. Additionally, the pump input polarization affects the generated continuum through the influence of polarization modulational instability. The experimental results are in good agreement with detailed numerical simulations. These findings demonstrate the importance of index-guiding photonic crystal fibers for the design of picosecond and nanosecond supercontinuum light sources. © 2002 Optical Society of America.