Role of Fe doping in tuning the band gap of TiO2 for the photo-oxidation-induced cytotoxicity paradigm

UV-light-induced electron-hole (e(-)/h(+)) pair generation with free radical production in TiO(2)-based nanoparticles is a major conceptual paradigm for biological injury. However, to date, this hypothesis has been difficult to experimentally verify due to the high energy of UV light that is intrinsically highly toxic to biological systems. Here, a versatile flame spray pyrolysis (FSP) synthetic process has been exploited to synthesize a library of iron-doped (0-10 wt%) TiO(2) nanoparticles. These particles have been tested for photoactivation-mediated cytotoxicity using near-visible light exposure. The reduction in TiO(2) band gap energy with incremental levels of Fe loading maintained the nanoparticle crystalline structure in spite of homogeneous Fe distribution (demonstrated by XRD, HRTEM, SAED, EFTEM, and EELS). Photochemical studies showed that band gap energy was reciprocally tuned proportional to the Fe content. The photo-oxidation capability of Fe-doped TiO(2) was found to increase during near-visible light exposure. Use of a macrophage cell line to evaluate cytotoxic and ROS production showed increased oxidant injury and cell death in parallel with a decrease in band gap energy. These findings demonstrate the importance of band gap energy in the phototoxic response of the cell to TiO(2) nanoparticles and reflect the potential of this material to generate adverse effects in humans and the environment during high-intensity light exposure.     

A Longitudinal Examination of Middle School Students' Understanding of the Equal Sign and Equivalent Equations

This longitudinal study investigated (a) middle school students' understanding of the equal sign, (b) students' performance solving equivalent equations problems, and (c) changes in students' understanding and performance over time. Written assessment data were collected from 81 students at four time points over a 3-year period. At the group level, understanding and performance improved over the middle school years. However, such improvements were gradual, with many students still showing weak understanding and poor performance at the end of grade 8. More sophisticated understanding of the equal sign was associated with better performance on equivalent equations problems. At the individual level, students displayed a variety of trajectories over the middle school years in their understanding of the equal sign and in their performance on equivalent equations problems. Further, students' performance on the equivalent equations problems varied as a function of when they acquired a sophisticated understanding of the equal sign. Those who acquired a relational understanding earlier were more successful at solving the equivalent equations problems at the end of grade 8.     

DNA cleavage on photoexposure at the d-d band in ternary copper(II) complexes using red-light laser

Ternary copper(II) complexes [Cu(L1)B](ClO4) (1, 2) and [Cu(L2)B](ClO4) (3, 4), where HL1 and HL2 are tridentate NSO- and ONO-donor Schiff bases and B is a heterocyclic base, viz. dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 1 and 3) or dipyrido[3,2-a:2',3'-c]phenazine (dppz, 2 and 4), were prepared and their DNA binding and photoinduced DNA cleavage activity studied. Complex 1, structurally characterized by single-crystal X-ray crystallography, shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the monoanionic L1 binds at the equatorial plane. The NN-donor dpq ligand exhibits an axial-equatorial binding mode. The complexes display good binding propensity to calf thymus DNA, giving a relative order 2 (NSO-dppz) > 4 (ONO-dppz) > 1 (NSO-dpq) > 3 (ONO-dpq). They cleave supercoiled pUC19 DNA to its nicked circular form when treated with 3-mercaptopropionic acid (MPA) by formation of hydroxyl radicals as the cleavage active species under dark reaction conditions. The photoinduced DNA cleavage activity of the complexes was investigated using UV radiation of 365 nm and red light of 633, 647.1, and 676.4 nm (CW He-Ne and Ar-Kr mixed gas ion laser sources) in the absence of MPA. Complexes 1 and 2, having photoactive NSO-donor Schiff base and dpq/dppz ligands, show dual photosensitizing effects involving both the photoactive ligands in the ternary structure with significantly better cleavage properties when compared to those of 3 and 4, having only photoactive dpq/dppz ligands. Involvement of singlet oxygen in the light-induced DNA cleavage reactions is proposed. A significant enhancement of the red-light-induced DNA cleavage activity is observed for the dpq and dppz complexes containing the sulfur ligand when compared to their earlier reported phen (1,10-phenanthroline) analogue. Enhancement of the cleavage activity on photoexposure at the d-d band indicates the occurrence of metal-assisted photosensitization processes involving the LMCT and d-d band in the ternary structure.     

Curcumin reduces α-synuclein induced cytotoxicity in Parkinson's disease cell model

Background  

Overexpression and abnormal accumulation of aggregated α-synuclein (αS) have been linked to Parkinson's disease (PD) and other synucleinopathies. αS can misfold and adopt a variety of morphologies but recent studies implicate oligomeric forms as the most cytotoxic species. Both genetic mutations and chronic exposure to neurotoxins increase αS aggregation and intracellular reactive oxygen species (ROS), leading to mitochondrial dysfunction and oxidative damage in PD cell models.     

Photosensitizer in a molecular bowl: steric protection enhancing the photonuclease activity of copper(II) scorpionates

Steric encumbrance caused by the tripodal ligand in the ternary tris(3-phenylpyrazolyl)borate copper(II) heterocyclic base complexes [Cu(B)(Tp(Ph))](ClO(4)) (B = dipyridoquinoxaline, dipyridophenazine) leads to efficient cleavage of supercoiled DNA to its relaxed form upon exposure to red light at 632.8 and 694 nm as a result of protection of the photosensitizer in the molecular bowl of the {Cu(Tp(Ph))} moiety, which generates singlet oxygen as the reactive species in a type-II process.     

Aqueous solution properties of amphiphilic triblock copolymer poly(p-dioxanone-co-l-lactide)-block-poly(ethylene glycol)

A poly(ethylene glycol) (PEG)-based new amphiphilic block copolymer bearing the poly(p-dioxanone-co-l-lactide) (PPDO/PLLA) hydrophobic moieties was prepared. Depending on the copolymer composition and molecular weights, solubility of the polymeric samples in water was varied. Its diluted aqueous solution properties were studied by viscometry, dye solubilization, ¹H-NMR and dynamic light scattering. 1,6-Diphenyl-1,3,5-hexatriene solubilization and ¹H-NMR spectra carried out in CDCl₃ and D₂O were used to prove the existence of hydrophobic domains as the core of micelle. Average particle size of 60-165 nm with low polydispersity and lower negative zeta (ξ) potential of −3 to −14 mV were observed on the aqueous copolymer dispersion.     

Efficient visible light induced nuclease activity of a ternary mono-1,10-phenanthroline copper(II) complex containing 2-(methylthio)ethylsalicylaldimine

Ternary Schiff base copper(II) complex [CuL(phen)](ClO(4)), where HL is 2-(methylthio)ethylsalicylaldimine and phen is 1,10-phenanthroline, has been prepared and structurally characterized by X-ray crystallography. The complex shows a CuN(3)OS coordination in a square-pyramidal (4 + 1) geometry with the sulfur as an equatorial ligand. The complex is an avid binder to double-stranded DNA in the minor groove and exhibits both photonuclease and chemical nuclease activity. When exposed to UV light of 312 nm (96 W) or visible light of 532 nm (125 W) under aerobic conditions, the complex causes significant cleavage of supercoiled pUC19 DNA in the absence of any externally added reducing agent or H(2)O(2).     

Transverse energy distributions in participant number model for ultra-relativistic heavy-ion collisions

The transverse energy distribution in ultra-relativistic heavy-ion collisions has been obtained as a convolution over the number of projectile and target participants. The latter is computed using the geometrical overlap model as a function of impact parameter. The data from 10 A GeV to 200 A GeV heavy ion beams on various targets in different pseudo-rapidity domains have been successfully described.     

HPTLC Method for Chemical Standardization of Sida Species and Estimation of the Alkaloid Ephedrine

JPC – Journal of Planar Chromatography – Modern TLC - The roots of Sida cordifolia, known as ‘Bala’ in the Ayurvedic system of medicine, are used to treat a variety of...