Excited state proton transfer and solvent relaxation of a 3-hydroxyflavone probe in lipid bilayers

The photophysics of a ratiometric fluorescent probe, N-[[4'- N, N-diethylamino-3-hydroxy-6-flavonyl]methyl]- N-methyl- N-(3-sulfopropyl)-1-dodecanaminium, inner salt (F2N12S), incorporated into phospholipid unilamellar vesicles is presented. The reconstructed time-resolved emission spectra (TRES) unravels a unique feature in the photophysics of this probe. TRES exhibit signatures of both an excited-state intramolecular proton transfer (ESIPT) and a dynamic Stokes shift associated with solvent relaxation in the lipid bilayer. The ESIPT is fast, being characterized by a risetime of approximately 30-40 ps that provides an equilibrium to be established between the excited normal (N*) and the ESIPT tautomer (T*) on a time scale of 100 ps. On the other hand, the solvent relaxation displays a bimodal decay kinetics with an average relaxation time of approximately 1 ns. The observed slow solvent relaxation dynamics likely embodies a response of nonspecific dipolar solvation coupled with formation of probe-water H-bonds as well as the relocation of the fluorophore in the lipid bilayer. Taking into account that ESIPT and solvent relaxation are governed by different physicochemical properties of the probe microenvironment, the present study provides a physical background for the multiparametric sensing of lipid bilayers using ESIPT based probes.     

Synthesis and coating of silica supported Nickel Oxide particles over ceramic pre-forms through sol–gel derived layered double hydroxides

Silica supported Nickel Oxide fine particles have been synthesized through sol–gel derived Ni–Al Layered Double Hydroxide (LDH) and coated over honeycomb ceramic pre-forms through dip-coating technique. The powder products of supported materials have low crystallinity, negative zeta potential, exhibit high dispersibility and suitable for further processing by coating techniques. The powder X-ray diffraction (XRD) patterns have shown that there is an increase of basal spacing by 3.02 Å in acetylacetonate intercalated LDH. The particles of <2 μm size increase with the rise of LDH component in the composite. The particles of NiO structure formed on decomposition of composites have crystallite size <20 nm. Due to the interlayer reduction of NiO crystallites, the unsupported LDH on calcination gives Ni⁰ particles of size around 4.18 nm. The Scanning Electron Microscopy (SEM) patterns of coated supported suspensions over ceramic substrates show formation of thin, crack free coats with uniform distribution of particles.     

Exploring Supramolecular Self‐Assembly of Tetraarylporphyrins by Halogen Bonding: Crystal Engineering with Diversely Functionalized Six‐Coordinate Tin(L)2–Porphyrin Tectons

This study targets the construction of porphyrin assemblies directed by halogen bonds, by utilizing a series of purposely synthesized Sn(axial ligand)₂–(5,10,15,20‐tetraarylporphyrin) [Sn(L)₂‐TArP] complexes as building units. The porphyrin moiety and the axial ligands in these compounds contain different combinations of complimentary molecular recognition functions. The former bears p‐iodophenyl, p‐bromophenyl, 4′‐pyridyl, or 3′‐pyridyl substituents at the meso positions of the porphyrin ring. The latter comprises either a carboxylate or hydroxy anchor for attachment to the porphyrin‐inserted tin ion and a pyridyl‐, benzotriazole‐, or halophenyl‐type aromatic residue as the potential binding site. The various complexes were structurally analyzed by single‐crystal X‐ray diffraction, accompanied by computational modeling evaluations. Halogen‐bonding interactions between the lateral aryl substituents of one unit of the porphyrin complex and the axial ligands of neighboring moieties was successfully expressed in several of the resulting samples. Their occurrence is affected by structural (for example, specific geometry of the six‐coordinate complexes) and electronic effects (for example, charge densities and electrostatic potentials). The shortest intermolecular I???N halogen‐bonding distance of 2.991 Å was observed between iodophenyl (porphyrin) and benzotriazole (axial ligand) moieties. Manifestation of halogen bonds in these relatively bulky compounds without further activation of the halophenyl donor groups by electron‐withdrawing substituents is particularly remarkable.     

Antibody modified Bovine Serum Albumin microspheres for targeted delivery of anticancer agent Gemcitabine

Inhibition of the EGFR signaling pathway is one of the attractive therapeutic targets for pancreatic cancer as recent studies demonstrated that EGFR is over‐expressed in pancreatic cancer. In this article we have demonstrated the design of targeted drug delivery system containing Bovine Serum Albumin (BSA) microspheres as delivery vehicle, gemcitabine as anticancer drug and anti‐EGFR (epidermal growth factor receptor) monoclonal antibody as targeting agent. The conjugated BSA microspheres were characterized by several physico‐chemical techniques such as scanning electron microscope, optical microscopy, fluorescent microscopy etc. Administration of these BSA microspheres containing gemcitabine and anti‐EGFR (BSA‐Gem‐EGFR) shows significant inhibition of pancreatic cancer cells (AsPC1) compared to the cells treated with only BSA microspheres, BSA with gemcitabine (BSA‐Gem), and free gemcitabine. This strategy could be used as a generalized approach for the treatment of pancreatic cancer along with other cancers which overexpress EGFR on cell surface. Copyright © 2012 John Wiley & Sons, Ltd.     

In situ reduction of graphitic oxide by amorphization of magnesium diboride for the superior thermo-optical property based nanofluid applications

The reaction of magnesium diboride with water results in an intermediate borohydride product which leads to the simultaneous reduction of graphitic oxide (GO) and the formation of magnesium hydroxide. In this work, the thermo-optical properties of magnesium diboride modified reduced graphene oxide–based nanofluids have been explored. The study primarily focuses on the reaction mechanism of magnesium diboride and GO by using liquid exfoliation technique. Suspension after liquid exfoliation mainly consisted of a turbid supernatant and precipitate which was composed of boron-based nanosheets (CBNs) and a composite of magnesium hydroxide and reduced graphene oxide (CBNs-rGO), respectively. Nanofluids were subsequently formulated from the obtained products of the reaction. CBNs form a stable suspension in water and ethylene glycol because of its attached borohydrides and hydroxyl hydrophilic sites. CBNs nanofluids show good thermal conductivity with poor light absorption properties in the visible wavelength range. Whereas, CBNs-rGO nanofluids show ~95% attenuation in the radiation with a significant enhancement of ~30% and 20% in thermal conductivity as compared with Deionized water– and ethylene glycol–based fluids, respectively.     

Through‐Space 1,4‐Palladium Migration and 1,2‐Aryl Shift: Direct Access to Dibenzo[a,c]carbazoles through a Triple CH Functionalization Cascade

A palladium‐catalyzed expeditious synthesis of dibenzofused carbazoles from readily available 2‐arylindoles and diaryliodonium salts is reported. Interestingly, after the electrophilic C3 palladation of indole, an unexpected “through‐space” 1,4‐palladium migration to the 2‐aryl moiety, by remote C?H bond activation followed by C?H arylation with diaryliodonium salt, and an unprecedented 1,2‐aryl shift take place. Finally, an intramolecular cross‐dehydrogenative coupling (CDC) at the C2 position affords dibenzo[a,c]carbazoles in high yields. Remarkably, the present migratory annulation occurs through three C?H bond activation one C?C bond cleavage, and the simultaneous construction of three new C?C bonds in a single operation.     

Realizing green phosphorescent light-emitting materials from rhenium(i) pyrazolato diimine complexes

Two neutral pyrazolato diimine rhenium(I) carbonyl complexes with formula [Re(CO)(3)(N-N)(btpz)] where N-N = 2,2'-bipyridine (1) and 1,10-phenanathroline (2), and btpz = 3,5-bis(trifluoromethyl) pyrazolate, were synthesized and characterized by elemental analysis, routine spectroscopic methods, and single-crystal X-ray diffraction study. Ground and excited state properties of these complexes were investigated by steady-state and time-resolved spectroscopies. Complexes 1 and 2 show photoluminescent emission in both solution and solid-state at room temperature, arising from metal to ligand charge-transfer (MLCT) transition with strong overlapping of intraligand pi --> pi transitions. The long-lived excited state lifetimes of complexes 1 and 2, which are on the order of microseconds, indicate the presence of phosphorescent emission. As these complexes hold the potential to serve as phosphors for organic light-emitting diodes (OLEDs), their electroluminescent performances were evaluated by employing them as dopants of various electron transport layer (ETL) or hole transport layer (HTL) hosts. For complex 1, a green electrophosphorescence emission centered at lambda(max) = 530 nm was observed at low turn-on voltage ( approximately 6 V) with luminous power efficiency of 0.72 lm/W, external quantum efficiency of 0.82%, and luminance of 2300 cd/m(2) at a current density of 100 mA/cm(2).     

Apoptogenic effects of β-sitosterol glucoside from Castanopsis indica leaves

β-Sitosterol glucoside (BSSG) is a natural biologically active substance isolated from the Castanopsis indica leaves. This study explored the apoptogenic mechanistic studies of BSSG against Ehrlich's ascites carcinoma (EAC) treated mice through morphological study, comet assay, flow cytometry (FACS) and Western blotting assay method. AO/EB staining and FACS analysis showed that BSSG possessed apoptosis induction activities on EAC cells. Dose dependent induction of DNA damage was observed after BSSG treatment. Increase the expression of apoptotic protein p53 and p21 in EAC, multiple downstream factors contributing to apoptosis pathway. The increase of caspase-9 and caspase-3 activities revealed that caspase was a key mediator of the apoptotic pathway induced by BSSG, and up-regulation of Bax and down-regulation of anti-apoptotic protein Bcl-2 resulted in the decrease of Bcl-2/Bax ratio. Owing to the combination of significant antitumour activity by inducing apoptosis, BSSG holds the promise of being an interesting chemo-preventive agent active in cancer therapy.     

Potential Therapeutic Target Protein Tyrosine Phosphatase-1B for Modulation of Insulin Resistance with Polyphenols and Its Quantitative Structure–Activity Relationship

The increase in the number of cases of type 2 diabetes mellitus (T2DM) and the complications associated with the side effects of chemical/synthetic drugs have raised concerns about the safety of the drugs. Hence, there is an urgent need to explore and identify natural bioactive compounds as alternative drugs. Protein tyrosine phosphatase 1B (PTP1B) functions as a negative regulator and is therefore considered as one of the key protein targets modulating insulin signaling and insulin resistance. This article deals with the screening of a database of polyphenols against PTP1B activity for the identification of a potential inhibitor. The research plan had two clear objectives. Under first objective, we conducted a quantitative structure–activity relationship analysis of flavonoids with PTP1B that revealed the strongest correlation (R² = 93.25%) between the number of aromatic bonds (naro) and inhibitory concentrations (IC₅₀) of PTP1B. The second objective emphasized the binding potential of the selected polyphenols against the activity of PTP1B using molecular docking, molecular dynamic (MD) simulation and free energy estimation. Among all the polyphenols, silydianin, a flavonolignan, was identified as a lead compound that possesses drug-likeness properties, has a higher negative binding energy of −7.235 kcal/mol and a pKd value of 5.2. The free energy-based binding affinity (ΔG) was estimated to be −7.02 kcal/mol. MD simulation revealed the stability of interacting residues (Gly183, Arg221, Thr263 and Asp265). The results demonstrated that the identified polyphenol, silydianin, could act as a promising natural PTP1B inhibitor that can modulate the insulin resistance.