The Reactivity of vic-dioximes Towards the [(H2O)(tap)2RuORu(tap)2(H2O)]2+ Ion {tap = 2-(m-tolylazo)pyridine} at Physiological pH

Kinetics of aqua ligand substitution from [(H₂O)(tap)₂RuORu(tap)₂(H₂O)]²⁺ {tap = 2-(m-tolylazo)pyridine}, by three vicinal dioximes, namely dimethylglyoxime (L¹H), 1,2-cyclohexanedione dioxime (L²H) and α-furil dioxime (L³H), have been studied spectrophotometrically in the 35–50 °C temperature range. The reaction was monitored at 560 nm where the absorbance between the reactant and product is at a maximum. At pH 7.4, the reaction has been found to proceed via two distinct consecutive steps, i.e., it shows a non-linear dependence on the concentration of ligands: the first process is [ligand] dependent but the second step is [ligand] independent. The rate constants for the processes are: k ₁ ~ 10^?3 s^?1 and k ₂ ~ 10^?4 s^?1. The activation parameters, calculated from Eyring plots, suggest an associative mechanism for the interaction process. From the temperature dependence of the outer sphere association equilibrium constants, the thermodynamic parameters were also calculated, which give negative ΔG° values at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. The product of the reaction has been characterized with the help of IR and ESI-mass spectroscopic analysis.     

Preparation of gamma cyclodextrin stabilized solid lipid nanoparticles (SLNS) using stearic acid–γ-cyclodextrin inclusion complex

The inclusion complexation behaviour of higher chain fatty acid, stearic acid (SA) with gamma cyclodextrin has been investigated. The inclusion complex was characterized by FT-IR, ¹H NMR, 2D NMR, XRD and DSC techniques. The results showed that the SA molecule was entrapped inside the gamma cyclodextrin cavity. Further, inclusion complex was treated with lopinavir at 85 °C and emulsified with hot water at 85 °C. The resulted nanoemulsion was cooled down to form solid lipid nanoparticles (SLNs) stabilized with gamma cyclodextrin. Prepared SLNs were having average particle size of 212.5 ± 4.8 nm, zeta potential of ?19.7 ± 0.66 mV and drug loading of 57.54 ± 0.62 %. The surface characteristics of SLNs were also observed with transmission electron microscopy and atomic force microscopy. Results indicate that inclusion complex of SA and gamma cyclodextrin can be used for SLNs preparation.     

Graphite epoxide

Oxidation of graphite may be carried out by reaction with meta-chloroperoxybenzoic acid to yield graphite epoxide. Scanning tunneling microscopy (STM) showed that the functionalization occurs at the edges rather than on the basal plane of the graphite. Quantification of the epoxide content is possible through the deepoxidation reaction using MeReO3/PPh3.     

Green fluorescent protein for in situ synthesis of highly uniform Au nanoparticles and monitoring protein denaturation

Purified recombinant green fluorescent protein (GFP) expressed in E. coli was used for single-step synthesis of gold nanoparticles (Au NPs) with extraordinary size specificity in aqueous medium. The fluorescence of GFP offered a probe for concomitant changes in the protein during the course of synthesis, in addition to the monitoring of the time-dependent formation of Au NPs by the surface plasmon resonance. Reaction of AuCl⁻₄ with the protein produced spherical Au NPs having diameters ranging from 5–70 nm. Remarkably, addition of 1.0×10⁻⁵ M AgNO₃ in the medium produced uniform spherical Au NPs with particle diameter of 2.2±0.5 nm. Fluorescence spectroscopic measurements suggest that during synthesis of Au NPs in absence of AgNO₃, partial denaturation of the protein occurred resulting in the lowering of fluorescence intensity. On the other hand, when the NPs were synthesized in the presence of AgNO₃ complete denaturation of the protein with complete loss of fluorescence could be observed, which was further confirmed by native and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). However, use of AgNO₃ only resulted neither in the formation of NPs nor had any significant effect on the fluorescence of GFP.     

Application of anionic micelle for dramatic enhancement in the quenching-based metal ion fluorosensing

We introduce a simple and efficient strategy to enhance the efficiency of a quenching-based fluorosensor for metal ions by several orders of magnitude by using commercially available anionic surfactants varying hydrophobic chain length. Anionic surfactants with a proper choice of hydrophobic chain length at their optimum concentrations are efficient to boost up the efficiency of copper ion sensor dramatically. This simple and convenient strategy is, in general, applicable to quenching-based fluorosensors, new or established, in aqueous solution. It is powerful enough to transform a virtually non-sensor fluorophore to a sensor with a commendable efficiency with the help of proper surfactant. Thus, in this communication, light has been thrown on the application of surfactants toward increasing fluorosensing efficiency of a quenching based sensor.     

Hydroxyapatite-supported palladium-catalyzed efficient synthesis of (E)-2-alkene-4-ynecarboxylic esters. Intense fluorescence emission of selected compounds

A simple procedure for the synthesis of substituted (E)-2-alkene-4-ynecarboxylic esters has been achieved using hydroxyapatite-supported palladium as efficient catalyst surface. The catalyst is recycled, and the turnover number (TON) based on Pd is 16000. A naphthyl-substituted derivative gives very intense fluorescence emission.     

Simultaneous Sensing of H2O,D2O and HOD through Peroxo Vibrations

Detection of HOD simultaneously in the presence of a mixture of H₂O and D₂O is still an experimental challenge. Till date, there is no literature report of simultaneous detection of H₂O, D₂O and HOD based on vibrational spectra. Herein we report simultaneous quantitative detection of H₂O, D₂O and HOD in the same reaction mixture with the help of bridged polynuclear peroxo complex in absence and presence of Au nanoparticles on the basis of a peroxide vibrational mode in resonance Raman and surface enhanced resonance Raman spectrum. We synthesize bridged polynuclear peroxo complex in different solvent mixture of H₂O and D₂O. Due to the formation of different nature of hydrogen bonding between peroxide and solvent molecules (H₂O, D₂O and HOD), vibrational frequency of peroxo bond is significantly affected. Mixtures of different H₂O and D₂O concentrations produce different HOD concentrations and that lead to different intensities of peaks positioned at 897, 823 and 867 cm⁻¹ indicating H₂O, D₂O and HOD, respectively. The lowest detection limits (LODs) were 0.028 mole fraction of D₂O in H₂O and 0.046 mole faction of H₂O in D₂O. In addition, for the first time the results revealed that the cis-peroxide forms two hydrogen bonds with solvent molecules.     

Impact of Structural Modification on the Photophysical Response of Benzoquinoline Fluorophores

Structural influence on the photophysical behavior of two pairs of molecular systems from the biologically potent benzoquinoline family, namely, dimethyl-3-(4-chlorophenyl)-3,4-dihydrobenzo[f]-quinoline-1,2-dicarboxylate, dimethyl-3-(2,6-dichlorophenyl)-3,4-dihydrobenzo[f]quinoline-1,2-dicarboxylate and their corresponding dehydrogenated analogues has been investigated exploiting experimental as well as computational techniques. The study unveils that dehydrogenation in the heterocyclic rings of the studied quinoline derivatives modifies their photophysics radically. Experimental observations imply that the photophysical behavior of the dihydro analogues is governed by the intramolecular charge transfer (ICT) process. However, the ICT process is restricted significantly by the dehydrogenation of the heterocyclic rings. Computational exertion leads to the proposition that the change in the electronic distribution in these molecular systems on dehydrogenation is the rationale behind the dramatic modification of their photophysics.     

Analysis of cell cultures of Taxus wallichiana using direct analysis in real-time mass spectrometric technique

The applicability of a new mass spectrometric technique, DART (direct analysis in real time) has been studied in the analysis of the calli of Taxus wallichiana. The intact callus samples were directly analyzed by holding them in the gap between the DART source and mass spectrometer for measurements. Five C-14 oxygenated taxoids were characterized from the analysis of the calli of the Taxus wallichiana almost instantaneously. The confirmation of the structures of the identified taxoids was made through their accurate molecular formula determinations.     

Hierarchical tuning of 1-D macro morphology by changing the composition of a binary hydrogel and its influence on the photoluminescence property

1-D morphological tuning in the riboflavine(R)-melamine(M) hydrogel system (from helical fiber to rod-like to tubular morphology) with an interesting photoluminescence property by changing the composition of the RM components.