Synthesis of mesogenic phthalocyanine-C60 donor-acceptor dyads designed for molecular heterojunction photovoltaic devices.

A series of phthalocyanine-C(60) dyads 2a-d was synthesized. Key steps in their synthesis are preparation of the low symmetry phthalocyanine intermediate by the statistical condensation of two phthalonitriles, and the final esterification of the fullerene derivative bearing a free COOH group. Structural characterization of the molecules in solution was performed by NMR spectroscopy, UV-vis spectroscopy and cyclic voltammetry. Preliminary studies suggest formation of liquid crystalline (LC) mesophases for some of the prepared dyads. To the best of our knowledge, this is the first example of LC phthalocyanine-C(60) dyads.

Use of DNA combing for studying DNA replication in vivo in yeast and mammalian cells.

Plasticity is an inherent feature of chromosomal DNA replication in eukaryotes. Potential origins of DNA replication are made in excess, but are used (fired) in a partly stochastic, partly programmed manner throughout the S phase of the cell cycle. Since most origins have a firing efficiency below 50%, population-based analysis methods yield a cumulative picture of origin activity (obtained by accretion) that does not accurately describe how chromosomes are replicated in single cells. DNA combing is a method that allows the alignment on silanized glass coverslips, at high density and with uniform stretching, of single DNA molecules in the Mb range. If this DNA is isolated from cells that have been labelled with halogenated nucleotides (BrdU, CldU, IdU), it is possible to determine the density and position of replication origins as well as the rate and symmetry of fork progression, quantitatively and on single DNA molecules. This chapter will successively describe (a) the preparation ofsilanized coverslips, (b) the incorporation of halogenated nucleotides in newly synthesized DNA in yeast and mammalian cell lines, (c) the preparation and combing of genomic DNA, and finally (d) the acquisition and analysis of single-molecule images to extract salient features of replication dynamics.

New semifluorinated dithiols self-assembled monolayers on a copper platform.

New alpha,omega-semifluorinated dithiols HS-(CH2)11-(CF2)n-(CH2)11-SH, called DTn, and corresponding dithioacetate molecules CH3COS-(CH2)11-(CF2)n-(CH2)11-SCOCH3, called DTAn ( n = 4, 6, 8), were synthesized and used to create self-assembled monolayers (SAMs) on both untreated copper surfaces and electrochemically reduced ones. The aim of this study is to assess the organization of the resulting SAMs, particularly the effect of the presence of two perhydrogenated segments surrounding the perfluorinated one, and the ability of these difunctional molecules to bind copper substrates by only one end per molecule. In each case, the organization of the SAM is rather poor and only DTA8 molecules seem to adopt an upright position on reduced copper. In addition, the layers have been investigated by cyclic voltammetry (CV) to assess their coverage. DT4 SAMs reveal a covering ratio higher than 99%.