Ternary copper complexes for photocleavage of DNA by red light: direct evidence for sulfur-to-copper charge transfer and d-d band involvement

A new class of ternary copper(II) complexes of formulation [Cu(L(n)B](ClO(4)) (1-4), where HL(n) is a NSO-donor Schiff base (HL(1), HL(2)) and B is a NN-donor heterocyclic base viz. 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmp), are prepared, structurally characterized, and their DNA binding and photocleavage activities studied in the presence of red light. Ternary complex [Cu(L(3))(phen)](ClO(4)) (5) containing an ONO-donor Schiff base and a binary complex [Cu(L(2))(2)] (6) are also prepared and structurally characterized for mechanistic investigations of the DNA cleavage reactions. While 1-4 have a square pyramidal (4 + 1) CuN(3)OS coordination geometry with the Schiff base bonded at the equatorial sites, 5 has a square pyramidal (4 + 1) geometry with CuN(3)O(2) coordination with the alcoholic oxygen at the axial site, and 6 has a square planar trans-CuN(2)O(2) geometry. Binding of the complexes 1-4 to calf thymus DNA shows the relative order: phen > dmp. Mechanistic investigations using distamycin reveal minor groove binding for the complexes. The phen complexes containing the Schiff base with a thiomethyl or thiophenyl moiety show red light induced photocleavage. The dmp complexes are essentially photonuclease inactive. Complexes 5 and 6 are cleavage inactive under similar photolytic conditions. A 10 microM solution of 1 displays a 72% cleavage of SC DNA (0.5 microg) on an exposure of 30 min using a 603 nm Nd:YAG pulsed laser (60 mJ/P) in Tris-HCl buffer (pH 7.2). Significant cleavage of 1 is also observed at 694 nm using a Ruby laser. Complex 1 is cleavage inactive under argon or nitrogen atmosphere. It shows a more enhanced cleavage in pure oxygen than in air. Enhancement of cleavage in D(2)O and inhibition with sodium azide addition indicate the possibility of the formation of singlet oxygen as a reactive intermediate leading to DNA cleavage. The d-d band excitation with red light shows significant enhancement of cleavage yield. The results indicate that the phen ligand is necessary for DNA binding of the complex. Both the sulfur-to-copper charge transfer band and copper d-d band excitations helped the DNA cleavage. While the absorption of a red photon induces a metal d-d transition, excitation at shorter visible wavelengths leads to the sulfur-to-copper charge transfer band excitation at the initial step of photocleavage. The excitation energy is subsequently transferred to ground state oxygen molecules to produce singlet oxygen that cleaves the DNA.     

Oxidations with IBX: benzyl halides to carbonyl compounds, and the one-pot conversion of olefins to 1,2-diketones

A variety of benzyl halides were converted to the corresponding aldehydes/ketones in respectable yields by IBX in DMSO at 65 °C. The bromohydrin reaction of olefins using NBS-H₂O in DMSO can be nicely adapted to IBX-mediated oxidation of benzyl halides in such a way that olefins are converted to the corresponding 1,2-diketones in good isolated yields in one-pot.     

A zero differential overlap study of chemical binding in ammonia-borane and carbony l-borane

A cndo/2D study of the charge distribution obtained through Mulliken population analysis in the ground state of the title compounds shows that the features of charge distribution found by severalab initio calculations are fairly well reproduced by this method. The one-particle density, the interference density at the mid-point of the bond axis and the kinetic part of the interference energy calculated through the deorthogonalized density matrices over a wide range of intermolecular separation between the donor and the acceptor show that the one-particle density and the interference density steadily grow with decreasing internuclear separation, while the kinetic interference energy starts with negative value at large distance, then decreases and passes through a minima near but above the equilibrium distance and then increases rapidly below it conforming to the characteristic general behaviour of the kinetic component of Morse curve. The orbital pairwise interference density and the corresponding kinetic energy components reveal that the orbitals involved in the covalent binding are σ_2p AO of B and 2S and σ_2p AO of N and C atoms in H₃B-NH₃ and H₃B-CO respectively.     

Kinetics of Polymerization of Methyl Methacrylate initiated by AIBN in the Presence of Acetophenone

The present investigation aims at estimating the retarding effect of acetophenone in the polymerization of methyl methacrylate initiated by α,α' -azobisisobutyronitrile in the temperature range of 50 to 80°C. The results are interpreted in terms of Tüdös kinetic parameter (β). The effects of varying concentrations of substrate, monomer, initiator, and salts have been investigated. A suitable reaction scheme and rate expression have been suggested on the basis of the experimental findings, and another kinetic parameter (K) to represent the reactivity of acetophenones toward the polymer radical has been obtained graphically.     

Computation of pressure drop for dilute gas-solid suspension across thin and thick orifices

The present work deals with the computation of the gas-solid two-phase flow pressure drop across thin and thick orifices for a vertically downward flow configuration at the higher limits of a dilute phase flow situation(0.01≤αs,in≤0.10).The Eulerian-Eulerian(two-fluid)model has been used in conjunction with the kinetic theory of granular flow with a four-way coupling approach.The validation of the solution process has been performed by comparing the computational result with the existing experimental data.It is observed that the two-phase flow pressure drop across the orifice increases with an increase in the thickness of the orifice,and the effect is more prominent at higher solid loading.The pressure drop is found to increase with an increase in the solid volume fraction.An increase in the Reynolds number or the area ratio increases the pressure drop.An increase in the size of the particles reduces the pressure drop across the orifice at both small and relatively large solid volume fractions.Finally,a two-phase multiplier has been proposed in terms of the relevant parameters,which can be useful to evaluate the gas-solid two-phase flow pressure drop across the orifice and can subsequently help to improve the system performance.     

An expedient protocol for conversion of olefins to α-bromo/iodoketones using IBX and NBS/NIS

A variety of olefins have been shown to undergo conversion to the corresponding α-bromo/iodoketones when reacted with NBS/NIS and IBX in DMSO at room temperature. While the reaction is found to occur rapidly with e-rich arylolefins leading to the corresponding haloketones in 65-95% yields in 0.3-3.0 h, those containing e-withdrawing groups are found to yield diketones concomitantly, such that the latter are the exclusive products over extended duration of the reactions.     

Multi-functional architectures supported on organostannoxane scaffolds

Organostannoxane cages and aggregates of well-defined composition and structure can be prepared by the reactions of organotin oxides or organotin oxide-hydroxides with protic acids. The utility of this strategy for the preparation of dendrimer-like molecules containing a stannoxane core and a functional periphery is described.     

Semiempirical evaluation of the global hardness of the atoms of 103 elements of the periodic table using the most probable radii as their size descriptors

Relying upon the fact that the density functional computation of the global hardness of the atoms of the elements are still at large and there is some mathematical in congruency between the theory and operational formula of finite difference approximation, we have suggested a radial‐dependent ansatz for evaluating global hardness of atoms as: η=a(7.2/r)+b (in eV), where, “a” and “b” are the constants and r is the absolute radius of atoms in angstrom unit. The ansatz is invoked to evaluate the global hardness of atoms of 103 element of the periodic table. The evaluated new set of global hardness is found to satisfy the sine qua non of a reasonable scale of hardness by exhibiting perfect periodicity of periods and groups and correlating the gross physicochemical properties of elements. The inertness of Hg and extreme reactivity Cs atoms are nicely correlated. The chemical reactivity and its variation in small steps in the series of lanthanide elements are also nicely reproduced. The results of the present semiempirical calculation also have strong correlation with the result of some sophisticated DFT calculation for a set of atoms. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Volumetric studies of some electrolytes in water and in aqueous sodium dodecylsulfate solutions at different temperatures

Abstract  

The apparent molar volumes (φ _v) of KCl, KNO₃, MgCl₂, and Mg(NO₃)₂ have been determined in water and in aqueous sodium dodecylsulfate solutions from density measurements at 303.15, 308.15, 313.15, 318.15, and 323.15 K. The limiting apparent molar volumes (j_v⁰ \varphi_{v}^{0} ) and experimental slopes (S _v) were derived from the Masson equation. The partial molar volume transfer (\Updelta [`(V)]<sub>\texttr</sub> ) (\Updelta {\bar{V}}_{\text{tr}} ) of the electrolytes were obtained from limiting apparent molar volume data from water to aqueous sodium dodecylsulfate solutions and have been interpreted in terms of ion–ion, hydrophilic–hydrophilic, and hydrophobic–hydrophobic interactions on the basis of a co-sphere overlap model. It is shown that the transfer volumes (\Updelta [`(V)]_\texttr ) (\Updelta {\bar{V}}_{\text{tr}} ) are positive and increase with increasing sodium dodecylsulfate concentration for all electrolytes. The structure making or breaking capacities of the electrolytes have been inferred from the sign of [∂² φ _v⁰/∂T ²]_p, i.e., the second derivative of the limiting apparent molar volume with respect to temperature at constant pressure. In water, KCl and KNO₃ exhibit structure breaking and MgCl₂ and Mg(NO₃)₂ exhibit structure making behavior. All the studied electrolytes were found to act as structure makers in aqueous sodium dodecylsulfate solutions.     

Gold nano-popcorn-based targeted diagnosis, nanotherapy treatment, and in situ monitoring of photothermal therapy response of prostate cancer cells using surface-enhanced Raman spectroscopy

Prostate cancer is the second leading cause of cancer-related death among the American male population, and the cost of treating prostate cancer patients is about $10 billion/year in the United States. Current treatments are mostly ineffective against advanced-stage prostate cancer and are often associated with severe side effects. Driven by these factors, we report a multifunctional, nanotechnology-driven, gold nano-popcorn-based surface-enhanced Raman scattering (SERS) assay for targeted sensing, nanotherapy treatment, and in situ monitoring of photothermal nanotherapy response during the therapy process. Our experimental data show that, in the presence of LNCaP human prostate cancer cells, multifunctional popcorn-shaped gold nanoparticles form several hot spots and provide a significant enhancement of the Raman signal intensity by several orders of magnitude (2.5 × 10(9)). As a result, it can recognize human prostate cancer cells at the 50-cells level. Our results indicate that the localized heating that occurs during near-infrared irradiation can cause irreparable cellular damage to the prostate cancer cells. Our in situ time-dependent results demonstrate for the first time that, by monitoring SERS intensity changes, one can monitor photothermal nanotherapy response during the therapy process. Possible mechanisms and operating principles of our SERS assay are discussed. Ultimately, this nanotechnology-driven assay could have enormous potential applications in rapid, on-site targeted sensing, nanotherapy treatment, and monitoring of the nanotherapy process, which are critical to providing effective treatment of cancer.