Diverted organic synthesis (DOS): accessing a new, natural product inspired, neurotrophically active scaffold through an intramolecular Pauson-Khand reaction

Drawing inspiration from the impressive neurotrophic activity exhibited by the natural product paecilomycine A, we have designed a new natural product-like scaffold employing an intramolecular Pauson-Khand reaction. Several compounds based on the new designer scaffold exhibited promising neurotrophic activity and are worthy of further biological evaluation. Our findings also highlight the importance of a DOS strategy in creating useful therapeutical leads.     

Radion tunneling in modified theories of gravity

We consider a five dimensional warped spacetime where the bulk geometry is governed by higher curvature F(R) gravity. In this model, we determine the modulus potential originating from the scalar degree of freedom of higher curvature gravity. In the presence of this potential, we investigate the possibility of modulus (radion) tunneling leading to an instability in the brane configuration. Our results reveal that the parametric regions where the tunneling probability is highly suppressed, corresponds to the parametric values required to resolve the gauge hierarchy problem.     

Mixed ligand palladium(II) complexes of oxalate and malonate with vitamin-B6 molecules: synthesis,crystal structure and kinetics

The synthesis of six mononuclear palladium complexes of general formula [Pd(ox)/(mal)L₂] and [Pd(ox)/(mal)L] (ox = oxalate, mal = malonate, both L and L are vitamin-B₆ molecules (I), L = pyridoxine, pyridoxal and L = pyridoxamine) has been achieved. The structures of these compounds were established by elemental analysis, i.r. and ¹³C-n.m.r. [Pd(oxalate)(pyridoxine)₂] was analyzed by single crystal X-ray diffraction. It exhibits square planar coordination with bond lengths 2.015 (2) Å for Pd—N and 2.010 (2) Å for Pd—O. The interaction of [Pd(ox)₂]^2– and [Pd(mal)₂]^2– with L has been followed kinetically in order to look into the nature of products and the mechanism of formation under the conditions [Pd^II-chelate] [L] and [L].     

Silver(II) Complexes of Tetraazamacrocycles: Studies on e.p.r. and Electron Transfer Kinetics with Thiosulfate Ion

The e.p.r. studies of Ag^II complexes of three tetraazamacrocycles, 1,4,8,11-tetraazacyclo-tetradecane (cyclam)(I), 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-teradecane-4,11-diene (Me₆CD)(II) and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-teradecane (Me₆Cy)(III) and the electron transfer between [Ag^II(cyclam)]²⁺ and thiosulfate ion are described. The e.p.r. studies reveal that the spectra are almost the same as those reported earlier, particularly, for polycrystalline material and are typical of a d ⁹ planar Ag^II complexes. Previous e.p.r. studies on these square planar polycrystalline complexes showed no ligand hyperfine splitting. Reinvestigation of the e.p.r. spectra of these complexes in both the solid state and in solution at room (T 297 K) and at low (T= 120 K) temperature reveals resolved hyperfine structures in solution for [Ag(Me₆CD)]²⁺ and [Ag(Me₆Cy)]²⁺ complexes. Surprisingly, such a structure was not observed in solutions of [Ag(cyclam)]²⁺. Computer simulations of the hyperfine structure observed in solutions are in good agreement with structural formulae proposed. The oxidation of thiosulfate ion by [Ag(cyclam)]²⁺ follows the rate law:–d/dt[Ag^II(cyclam)²⁺]=(k ₁ Q ₁[H+]+k ₂ Q ₂ K _a2)/([H+]+K _a2)[Ag^II(cyclam)²⁺][S₂O₃ ^2–] and an inner-sphere mechanism is proposed, based on the spectral and kinetic evidence.     

Detection of OH radical in laser induced photodissociation of tetrahydrofuran at 193 nm

On excitation at 193 nm, tetrahydrofuran (THF) generates OH as one of the photodissociation products. The nascent energy state distribution of the OH radical was measured employing laser induced fluorescence technique. It is observed that the OH radical is formed mostly in the ground vibrational level, with low rotational excitation (approximately 3%). The rotational distribution of OH (v"=0,J) is characterized by rotational temperature of 1250+/-140 K. Two spin-orbit states, 2Pi3/2 and 2Pi1/2 of OH are populated statistically. But, there is a preferential population in Lambda doublet levels. For all rotational numbers, the 2Pi+(A') levels are preferred to the 2Pi-(A") levels. The relative translational energy associated with the photoproducts in the OH channel is calculated to be 17.4+/-2.2 kcal mol-1, giving an fT value of approximately 36%, and the remaining 61% of the available energy is distributed in the internal modes of the other photofragment, i.e., C4H7. The observed distribution of the available energy agrees well with a hybrid model of energy partitioning, predicting an exit barrier of approximately 16 kcal mol-1. Based on both ab initio molecular orbital calculations and experimental results, a plausible mechanism for OH formation is proposed. The mechanism involves three steps, the C-O bond cleavage of the ring, H atom migration to the O atom, and the C-OH bond scission, in sequence, to generate OH from the ground electronic state of THF. Besides this high energy reaction channel, other photodissociation channels of THF have been identified by detecting the stable products, using Fourier transform infrared and gas chromatography.     

Photophysical and Duplex‐DNA‐Binding Properties of Distamycin Dimers Based on 4,4′‐ and 2,2′‐Dialkoxyazobenzenes as the Core

Distamycin‐based tetrapeptide ( 1 ) was covalently tethered to both ends of the central dihydroxyazobenzene moiety at either the 2,2′ or 4,4′ positions. This afforded two isomeric, distamycin–azobenzene–distamycin systems, 2 (para) and 3 (ortho), both of them being photoisomerizable. Illumination of these conjugates in solution at approximately 360 nm induced photoisomerization and the time course of the process was followed by UV/Vis and ¹H NMR spectroscopy. The kinetics of the thermal reversion at various temperatures of cis to trans isomers of the conjugates obtained after photoillumination were also examined. This afforded the respective thermal‐activation parameters. Both the molecular architecture and the location of the substituent around the core azobenzene determined the rate and activation‐energy barrier for the cis‐to‐trans back‐isomerization of these conjugates in solution. Duplex–DNA binding of the conjugates and the changes in DNA‐binding efficiency upon photoisomerization was also examined by CD spectroscopy, thermal denaturation studies, and a Hoechst displacement assay. The conjugate 2 showed higher DNA‐binding affinity and a greater change in the DNA‐binding efficiency upon photoisomerization compared with its 2,2′‐disubstituted counterpart. The experimental findings were substantiated by using molecular‐docking studies involving each conjugate with a model duplex d[(GC(AT)₁₀CG)]₂ DNA molecule.     

Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for blood cancer detection

We report results of the studies relating to controlled deposition of the amino-functionalized silica-coated zinc oxide (Am-Si@ZnO) nano-assemblies onto an indium tin oxide (ITO) coated glass substrate using Langmuir-Blodgett (LB) technique. The monolayers have been deposited by transferring the spread solution of Am-Si@ZnO stearic acid prepared in chloroform at the air-water interface, at optimized pressure (16 mN/m), concentration (10 mg/ml) and temperature (23 °C). The high-resolution transmission electron microscopic studies of the Am-Si@ZnO nanocomposite reveal that the nanoparticles have a microscopic structure comprising of hexagonal assemblies of ZnO with typical dimensions of 30 nm. The surface morphology of the LB multilayer observed by scanning electron microscopy shows uniform surface of the Am-Si@ZnO film in the nanometer range (<80 nm). These electrodes have been utilized for chronic myelogenous leukemia (CML) detection by covalently immobilizing the amino-terminated oligonucleotide probe sequence via glutaraldehyde as a crosslinker. The response studies of these fabricated electrodes carried out using electrochemical impedance spectroscopy show that this Am-Si@ZnO LB film based nucleic acid sensor exhibits a linear response to complementary DNA (10⁻⁶–10⁻¹⁶ M) with a detection limit of 1 × 10⁻¹⁶ M. This fabricated platform is validated with clinical samples of CML positive patients and the results demonstrate its immense potential for clinical diagnosis.     

Metal-complex/DNA conjugates: a versatile building block for DNA nanoarrays

The use of DNA networks as templates for forming nanoarrays of metallic centres shows an exciting potential to generate addressable nanostructures. Inorganic units can be photoactive, electroactive and/or can possess magnetic and catalytic properties and can adopt different spatial arrangements due to their varied coordination nature. All these properties influence both the structure and function of passive DNA scaffolds and provide DNA nanostructures as a new platform for new materials in emerging technologies, such as nanotechnology, biosensing or biocomputing.     

Solutions to Integro-differential Problems Arising on Pricing Options in a Lévy Market

We study an integro-differential parabolic problem arising in Financial Mathematics. Under suitable conditions, we prove the existence of solutions for a multi-asset case in a general domain using the method of upper and lower solutions and a diagonal argument. We also model the jump in the related integro differential equation and give a solution procedure for that model assuming that the brownian motions are not correlated. For a bounded domain, this model for the jump gives an elegant expression of the solution in terms of hyper-spherical harmonics.     

Quantum electron transfer processes induced by thermo-coherent state

When the reactant surface is not in a thermal equilibrium, but in a thermo-coherent state we have derived the rate and discussed about the quantum features of the rate. In the limit of very low and very high temperature the expressions are derived analytically and compared with the case of thermal distribution. We have investigated the dependence of temperature on the rate due to displacement, distortion of the harmonic potential energy surfaces of the reactant and product manifold.