Flavonoid-DNA binding studies and thermodynamic parameters

Interactional studies of new flavonoid derivatives (Fl) with chicken blood ds.DNA were investigated spectrophotometrically in DMSO-H2O (9:1 v/v) at various temperatures. Spectral parameters suggest considerable binding between the flavonoid derivatives studied and ds.DNA. The binding constant values lie in the enhanced-binding range. Thermodynamic parameters obtained from UV studies also point to strong spontaneous binding of Fl with ds.DNA. Viscometric studies complimented the UV results where a small linear increase in relative viscosity of the DNA solution was observed with added optimal flavonoid concentration. An overall mixed mode of interaction (intercalative plus groove binding) is proposed between DNA and flavonoids. Conclusively, investigated flavonoid derivatives are found to be strong DNA binders and seem to be promising drug candidates like their natural analogues.     

Shedding light on the laser wavelength effect in Raman analysis of skin epidermises

Confocal Raman microspectroscopy is a promising technique which enables measuring the molecular composition of the skin layers, non-destructively and without extrinsic markers. The Raman approach is increasingly used in skin research but with various experimental conditions. In addition to the different skin types, one of the varying parameters is the wavelength of laser excitation. This parameter contributes strongly in the skin Raman response. The present work aimed to evaluate this effect for 3 different wavelengths, 532, 633 and 785 nm, on pig ear skin models. The Raman signal was assessed in the spectral fingerprint region. According to the Raman response for stability, repeatability, variability and fluorescence contribution, the 785 nm excitation wavelength was shown to be the most suitable for epidermis depth profiling in the fingerprint region.     

Carbene complexes of rhodium and iridium from tripodal N-heterocyclic carbene ligands: synthesis and catalytic properties

Two tripodal trisimidazolium ligand precursors have been tested in the synthesis of new N-heterocyclic carbene rhodium and iridium complexes. [Tris(3-methylbenzimidazolium-1-yl)]methane sulfate gave products with coordination of the decomposed precursor. [1,1,1-Tris(3-butylimidazolium-1-yl)methyl]ethane trichloride (TIMEH(3)(Bu)) coordinated to the metal in a chelate and bridged-chelate form, depending on the reaction conditions. The crystal structures of two of the products are described. The compounds resulting from the coordination with TIME(Bu) were tested in the catalytic hydrosilylation of terminal alkynes.     

Imidazolium Based Probes for Recognition of Biologically and Medically Relevant Anions

The imidazolium derivatives due to their positive charge possess one of the most polarized and positively charged proton at C2‐H to form strong ionic hydrogen bond (also termed as double ionic hydrogen bond) with anions and also provide opportunities for anion – π interactions with electron‐deficient imidazolium ring. In the present review article, imidazolium based molecular probes for their ability to recognize inorganic anions like halides, cyanide, perchlorate, carboxylic acids, phosphate, sulfate etc. and their derived molecules viz. nucleotides, DNA, RNA, surfactants, proteins, etc have been discussed. The review covers the literature published after year 2009 and has > 130 references. The previous literature has already been discussed by Yoon et al. in two review articles published in Chem. Soc. Rev. 2006 and 2010.     

Highly stable Cp*-Ir(III) complexes with N-heterocyclic carbene ligands as C-H activation catalysts for the deuteration of organic molecules

The preparation of a series of complexes of the type CpIrX2(NHC) provides effective catalysts for the H/D exchange of a wide range of organic molecules in methanol-d4. The reaction proceeds with higher yields under milder reaction conditions than previous CpIr systems reported thus far. For comparative purposes, we also studied the catalytic activity of CpIrCl2(PMe3) under the same reaction conditions. The molecular structures of two of the new CpIr(NHC) complexes are described.     

Microwave assisted non-aqueous sol–gel synthesis of LiNiPO4 and its copper doped analogues

A series of single phase LiNi_(1?x)Cu_xPO₄ (0 < x < 0.99) was successfully synthesized by non-aqueous sol–gel method followed by microwave (MW) annealing. The advantage of MW short span annealing is obvious from the nanometer sized particles compared to reported microparticles. XRD, IR and SEM studies were conducted to investigate the phase purity, crystal structure, lattice parameters and morphology respectively. It was found that 10 min of microwave annealing is a time and cost effective approach to produce single phase compositions at low temperature. X-ray studies confirmed the single phase formation of pure and the doped analogues which were found to be iso-structural with the parent LiNiPO₄ compound. The cell parameters with the addition of copper content were in accord with the Vegards law. Impedance studies pointed toward enhanced electrical properties of doped samples as compared to the undoped one.     

Conformational analysis by UV spectroscopy: the decisive contribution of environment-induced electronic Stark effects

UV chromophores are frequently used as probes of the molecular structure. In particular, they are sensitive to the electric field generated by the molecular environment, resulting in the observation of Stark effects on UV spectra. While these environment-induced electronic Stark effects (EI-ESE) are already used for conformational analysis in the condensed phase, this work explores the potential of such an approach when performed at much higher conformational resolution in the gas phase. By investigating model alkali benzylacetate and 4-phenylbutyrate ion pairs, where the electric field applied to the phenyl ring is chemically tuned by changing the nature of the alkali cation, this work demonstrates that precise conformational assignments can be proposed based on the correlation between the conformation-dependent calculated electric fields and the frequency of the electronic transitions observed in the experimental UV spectra. Remarkably, the sole analysis of Stark effects and fragmentation patterns in mass-selected UV spectra provided an accurate and complete conformational analysis, where spectral differences as small as a few cm⁻¹ between electronic transitions were rationalized. This case study illustrates that the identification of EI-ESE together with their interpretation at the modest cost of a ground state electric field calculation qualify UV spectroscopy as a powerful tool for conformational analysis.

The correlation between experimental electronic transitions and calculated electric fields leads to precise conformational assignments and opens up the possibility of interpreting electronic spectra in a quantitative manner at the wavenumber scale.     

The experimental design for computing the harmonic and anharmonic force constant matrices of polyatomic molecules

In the present work we propose a numerical approach to estimate the harmonic and anharmonic force constant matrices, supposing we are able to compute analytically the first order derivative vector of the potential energy surface with respect to the internal coordinates. We use a polynomial least square fit to interpolate this gradient in the stationary point region. The structure of the regression matrix shows that the harmonic force constant matrix may be obtained even for large molecules; the evaluation of the anharmonic contributions request slightly more labor but is possible for 5 to 7 atoms. The present work is applicable even at the CI level and the number of computations remains small. We use the experimental planification to select the geometries to be computed in order to improve the estimation of the regression coefficients i.e. this means to lower their variance.chercheur qualifié du Fonds National Belge de la Recherche Scientifique.