Determining the adsorptive and catalytic properties of strained metal surfaces using adsorption-induced stress

We demonstrate a model for determining the adsorptive and catalytic properties of strained metal surfaces based on linear elastic theory, using first-principles calculations of CO adsorption on Au and K surfaces and CO dissociation on Ru surface. The model involves a single calculation of the adsorption-induced surface stress on the unstrained metal surface, which determines quantitatively how adsorption energy changes with external strain. The model is generally applicable to both transition- and non-transition-metal surfaces, as well as to different adsorption sites on the same surface. Extending the model to both the reactant and transition state of surface reactions should allow determination of the effect of strain on surface reactivity.     

Spinning cone water film power meter for high-power CO2 lasers

A laser power meter based on water as an absorbing medium has been developed to measure multi-kilowatt CO₂ laser power with high sensitivity and accuracy. Water absorbs CO₂ laser radiation readily within a very thin layer. Though water has large thermal capacity, due to short absorption length, it could vapourize at high laser powers. In order to circumvent this problem, this power meter has a centre cone and a rapidly spinning water film as the calorimetric medium. The unique feature in this development is the centre cone, which diverges the beam and reduces the power density thus reduces the possibility of vapourization. This minimizes the error in measurements. Due to the rapidly moving fluid film, it exhibits fast response at low as well as high power levels.     

Dually Responsive Poly(N-vinylcaprolactam)-b-poly(dimethylsiloxane)-b-poly(N-vinylcaprolactam) Polymersomes for Controlled Delivery

Limited tissue selectivity and targeting of anticancer therapeutics in systemic administration can produce harmful side effects in the body. Various polymer nano-vehicles have been developed to encapsulate therapeutics and prevent premature drug release. Dually responsive polymeric vesicles (polymersomes) assembled from temperature-/pH-sensitive block copolymers are particularly interesting for the delivery of encapsulated therapeutics to targeted tumors and inflamed tissues. We have previously demonstrated that temperature-responsive poly(N-vinylcaprolactam) (PVCL)-b-poly(dimethylsiloxane) (PDMS)-b-PVCL polymersomes exhibit high loading efficiency of anticancer therapeutics in physiological conditions. However, the in-vivo toxicity of these polymersomes as biocompatible materials has not yet been explored. Nevertheless, developing an advanced therapeutic nanocarrier must provide the knowledge of possible risks from the material’s toxicity to support its future clinical research in humans. Herein, we studied pH-induced degradation of PVCL₁₀-b-PDMS₆₅-b-PVCL₁₀ vesicles in-situ and their dually (pH- and temperature-) responsive release of the anticancer drug, doxorubicin, using NMR, DLS, TEM, and absorbance spectroscopy. The toxic potential of the polymersomes was evaluated in-vivo by intravenous injection (40 mg kg⁻¹ single dose) of PVCL₁₀-PDMS₆₅-PVCL₁₀ vesicles to mice. The sub-acute toxicity study (14 days) included gravimetric, histological, and hematological analyses and provided evidence for good biocompatibility and non-toxicity of the biomaterial. These results show the potential of these vesicles to be used in clinical research.     

Highly convergent one-pot four-component regioselective synthesis of 4H-benzo[f]chromenes via annulation of β-oxodithioesters

Highly efficient regioselective protocol for the synthesis of hitherto unreported 4H-benzo[f]chromenes has been developed by one-pot four-component coupling of aromatic aldehydes, β-naphthol, β-oxodithioesters, and primary alcohols in the presence of InCl₃. This transformation presumably proceeds via domino Knoevenagel condensation/Michael addition/intramolecular cyclodehydration/transesterification sequence creating four new bonds and one stereocenter in a single operation. Further, alcohol plays dual role as a reactant as well as reaction medium.     

Expanding the repertoire of pyrrolidyl PNA analogues for DNA/RNA hybridization selectivity: aminoethylpyrrolidinone PNA (aepone-PNA)

New PNA analogues derived from aminoethylpyrrolidin-5-one backbone show stabilization of aepone-PNA:DNA hybrids and destabilization of the corresponding RNA hybrids compared to unmodified PNA.     

Effect of Glass Substrates on the Formation of Gold-Silver Colloids in Nanocomposite Thin Films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag—Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO₂ thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn²⁺ state on the glass surface, which oxidizes into Sn⁴⁺ during heat treatment, reducing Ag⁺ into silver colloids.     

β-Cyclodextrin-polyurethane polymer as solid phase extraction material for the analysis of carcinogenic aromatic amines

β-Cyclodextrin-polyurethane (β-CDPU) polymer was synthesized by the reaction of β-cyclodextrin with hexamethylene diisocyanate in dry dimethylformamide and used as a sorbent for the solid phase extraction (SPE) of carcinogenic aromatic amines from water. The polymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and particle size analysis. The separation and quantification was performed by Liquid chromatography with RP-C₁₈ column and diode array detection using standard arylamines for quantification. When compared with commercially available sorbents, β-CDPU gave better recovery for the aromatic amines. From the variation of pH of the extractant from 4.0 to 8.5 recovery was highest at pH 8.5. The breakthrough volume has been ascertained to be 100 ml for 200 mg of the resin. The new SPE material offers better recovery and estimation of banned arylamines.     

Impact of carbamylation on type I collagen conformational structure and its ability to activate human polymorphonuclear neutrophils

Carbamylation by urea-derived cyanate is a posttranslational modification of proteins increasing during chronic renal insufficiency, which alters structural and functional properties of proteins and modifies their interactions with cells. We report here the major structural alterations of type I collagen induced by carbamylation. Biophysical methods revealed that carbamylated collagen retained its triple-helical structure, but that slight changes destabilized some regions within the triple helix and decreased its ability to polymerize into normal fibrils. These changes were associated with the incapacity of carbamylated collagen to stimulate polymorphonuclear neutrophil oxidative functions. This process involved their interaction with LFA-1 integrin, but no subsequent p(125)FAK phosphorylation. Carbamylation of collagen might alter interactions between collagen and inflammatory cells in vivo and interfere with the normal remodeling of extracellular matrix, thus participating in the pathophysiological processes occurring during renal insufficiency.