Complexes of Co (II) and Cu (II) with nonsteroidal anticancer drug Letrozole and their interaction with DNA and BSA by spectroscopic methods and cytotoxic activity

DNA and BSA binding properties of mononuclear Co (II) and Cu (II) complexes containing letrozole [M(Le)₄Cl₂]·(H2O)](Le=[4,4-(1H-1,2,4-triazol-1-ylmethylene)bisbenzonitrile] have been investigated under physiological conditions. The interaction ability of the two complexes with native calf thymus DNA(CT-DNA) has been monitored as a function of the metal complex-DNA molar ratio by UV–Vis absorption spectrophotometry, fluorescence spectroscopy, circular dichroism(CD) and thermal denaturation studies. The intrinsic binding constants, K_b, of complexes 1 and 2 with CT-DNA, obtained from UV–Vis absorption studies, were 3.15 ± 0.02 × 10⁴ and 4.37 ± 0.02 × 10⁴ M^?1, respectively. The addition of the complexes to CT-DNA (1:2) leads to an increase in the melting temperature of DNA up to around 4 °C, which has revealed that complexes could interact with DNA through intercalation mode. Fluorimetric studies have been performed using methylene blue (MB) as a fluorescence probe and competitive studies have shown the ability of the complexes to displace the DNA-bound MB, suggesting competition with MB. To explore the potential biological value of the complexes, the binding interaction between Co (II) and Cu (II) complexes and bovine serum albumin (BSA) has also been studied by fluorescence spectroscopy. The results indicate that the reaction between the complexes and BSA is a static quenching procedure. The site marker displacement experiment has suggested the location of the complexes binding to BSA at Sudlow’s site I in subdomain IIA. Finally, MTT assay studies have shown that the bioactive complexes exert significantly high selective dose-dependent cytotoxicity against a panel of cancer cell lines including MCF-7, JURKAT, SKOV3 and U87.     

Approximating Probability Distributions Using Small Sample Spaces

We formulate the notion of a "good approximation" to a probability distribution over a finite abelian group ?. The quality of the approximating distribution is characterized by a parameter ɛ which is a bound on the difference between corresponding Fourier coefficients of the two distributions. It is also required that the sample space of the approximating distribution be of size polynomial in and 1/ɛ. Such approximations are useful in reducing or eliminating the use of randomness in certain randomized algorithms. We demonstrate the existence of such good approximations to arbitrary distributions. In the case of n random variables distributed uniformly and independently over the range , we provide an efficient construction of a good approximation. The approximation constructed has the property that any linear combination of the random variables (modulo d) has essentially the same behavior under the approximating distribution as it does under the uniform distribution over . Our analysis is based on Weil's character sum estimates. We apply this result to the construction of a non-binary linear code where the alphabet symbols appear almost uniformly in each non-zero code-word. Received: September 22, 1990/Revised: First revision November 11, 1990; last revision November 10, 1997     

Theoretical study in [C2H4–Tl]+ and [C2H2–Tl]+ complexes

We studied the attraction between [C₂H_n] and Tl(I) in the hypothetical [C₂H_n–Tl]⁺ complexes (n = 2,4) using ab initio methodology. We found that the changes around the equilibrium distance C–Tl and in the interaction energies are sensitive to the electron correlation potential. We evaluated these effects using several levels of theory, including Hartree–Fock (HF), second‐order Møller–Plesset (MP2), MP4, coupled cluster singles and doubles CCSD(T), and local density approximation augmented by nonlocal corrections for exchange and correlation due to Becke and Perdew (LDA/BP). The obtained interaction energies differences at the equilibrium distance R_e (C–Tl) range from 33 and 46 kJ/mol at the different levels used. These results indicate that the interaction between olefinic systems and Tl(I) are a real minimum on the potential energy surfaces (PES). We can predict that these new complexes are viable for synthesizing. At long distances, the behavior of the [C₂H_n]–Tl⁺ interaction may be related mainly to charge‐induced dipole and dispersion terms, both involving the individual properties of the olefinic π‐system and thallium ion. However, the charge‐induced dipole term (R^?4) is found as the principal contribution in the stability at long and short distances. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

An NMR study of mobility in a crystalline side‐chain comblike polymer

Carbon‐13 spin–lattice relaxation times are measured for poly(octadecyl acrylate) above and below the melting point of the crystalline side chains. The chain backbone has long spin–lattice relaxation times below the melting point that shorten by more than an order of magnitude as the melting point range is traversed. Below the melting point, the backbone is nearly immobilized with spin–lattice relaxation changing very slowly with temperature. Above the melting point, the shorter spin–lattice relaxation times are typical of a rubber above the glass transition and decrease with increasing temperature. The methylene groups in the side chain are quite mobile well below the melting point, indicating fairly rapid anisotropic motion within the crystal. The methyl group at the end of the chain and the adjacent methylene group have longer spin–lattice relaxation times, indicating the greatest side‐chain mobility at the end, which is in the middle of the crystal structure. The side‐chain carbon adjacent to the carbonyl group is as mobile as the majority of the side‐chain carbon, indicating side‐chain mobility extends to all of the side‐chain CH₂ groups. The abrupt transition in the mobility of the backbone is not typical of the amorphous phase in a semicrystalline polymer where the backbone units can crystallize. The close proximity of every backbone segment to the crystalline domain locks backbone segmental motion below the melting point. Melting and crystallization of the side chains switch segmental motion of the backbone on and off. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1548–1552, 2001     

Integrated polymers (PVCi/PMATRIFE) microring resonators for low power tunable filters

In this paper we present optical and thermo-optical characterization results of integrated filters based on micro-ring resonators fabricated with a couple of polymers “PVCI/PMATRIFE”. Their high index contrast (Δn～0.15 at the wavelength of 1550 nm) allows to make small size waveguides with cross sections of 1.5×1.5 μm². The study of the impact of different gaps on the extinction ratio and FWHM (full width at half maximum) of filters leads to a better design. First experiments of thermal tunability of the microring filter using a thermo-electric cooler (TEC) are also reported giving a 5 nm shift of the dropped wavelength for a temperature change of 40 K. The fabrication of gold electrodes on microrings is reported and the electrical power required for the tuning of the drop wavelength of 0.0055 nm/1 mW show that with an optimized electrode design the consumption will be low.     

On Two Dimensional Packing

The paper considerspacking of rectanglesinto an infinite bin. Similar to theTetris game, the rectangles arrive from the top and, once placed, cannot be moved again. The rectangles are moved inside the bin to reach their place. For the case in which rotations are allowed, we design an algorithm whose performance ratio is constant. In contrast, if rotations are not allowed, we show that no algorithm of constant ratio exists. For this case we design an algorithm with performance ratio ofO(log(1/)), where is the minimum width of any rectangle. We also show that no algorithm can achieve a better ratio than for this case.     

The formulation and performance of a perturbative correction to the perfect quadruples model

A recently published alternative hierarchy of coupled-cluster approximations is reformulated as a perturbative correction. A single variant, a model for the total electronic energy based on the perfect quadruples model, is explored in detail. The computational scaling of the method developed is the same as canonical second order Mo?ller-Plesset perturbation theory (fifth order in the number of molecular orbitals), but its accuracy competes with the high-accuracy, high-cost standard CCSD(T), even when the latter is allowed to break spin-symmetry. The variation presented can be implemented without explicit calculation and storage of the most expensive energy contributions, thereby improving the range of systems which can be treated. The performance and scaling of the method are demonstrated with calculations on the water, fluorine, and oxirane molecules, and compared to the parent model.