Nucleophilic proteolytic antibodies

Proteolytic antibodies appear to utilizecatalytic mechanisms akin to nonantibody serine proteases, assessed from mutagenesis and protease-inhibitor studies. The catalytic efficiency derives substantially from the ability to recognize the ground state with high affinity. Because the proteolytic activity is germline-encoded, catalysts with specificity for virtually any target polypeptide could potentially be developed by applying appropriate immunogens and selection strategies. Analysis of transition-state stabilizing interactions suggests that chemical reactivity ofactive-site serine residues is an important contributor to catalysis. A prototype antigen analog capable of reacting covalently with nucleophilic serine residues permitted enrichment of the catalysts from a phage-displayed lupus light-chain library. Further mechanistic developments in understanding proteolytic antibodies may lead to the isolation of catalysts suitable for passive immunotherapy of major diseases, and elicitation of catalytic immunity as a component of prophylactic vaccination.     

One-electron redox reactions of troxerutin in aqueous solutions

The oxidation of flavonoids is of great interest because of their action as antioxidants with the ability to scavenge radicals by means of electron-transfer processes. The redox reactions of the flavonoid derivative troxerutin, (2-[3,4-bis-(2-hydroxyethoxy) phenyl]-3[[6-deoxy-α-L-manno-pyranosyl)-β-(D-glucopyranosyl]-oxy]-5-hydroxy-7-(2-hydroxyethoxy)-4H-1-benzo-pyran-4-one), were investigated over a wide range of conditions, using pulse radiolysis and cyclic voltammetry. The oxidation mechanism proceeds in sequential steps. One-electron redox potentials for troxerutin were found to be +1.196, +0.846 and −0.634 V vs. NHE.     

Redox reactions of disulfiram: a pulse-radiolysis study

Redox reactions of disulfiram (DSF) were studied in aqueous solutions using the pulse-radiolysis technique. Reactions of DSF with one-electron oxidants Br₂ ^- and N₃, generated pulse radiolytically in aqueous solution at pH 7, yielded a transient (_max = 480 nm) which exhibited the characteristics of a disulphide cation radical and decayed by second-order kinetics. Reactions of DSF with halogenated peroxyl radicals CCl₃O₂, CHCl₂O₂, CH₂ClO₂ and CBr₃O₂ led to the formation of an adduct absorbing at 580 nm. The reduction potential was estimated to be 1.24 ± 0.06 V vs. NHE.     

Stereoselective synthesis of α-glucosides from 3-O-propargyl protected glucal exploiting the alkynophilicity of AuCl3

The stereoselective synthesis of 2,3-unsaturated α-d-glucosides by the S_N2′ addition of diverse aglycones onto 4,6-di-O-benzyl-3-O-propargyl glucal was achieved using a catalytic quantity of AuCl₃. The Au catalyzed reaction was explored using various aliphatic, aromatic, alicyclic and monosaccharide aglycones. The current protocol tolerates diverse functional groups and is highly stereoselective, fast, catalytic and mild.     

Sulfonation of arylamines: Part 12. Kinetics of thermal decomposition of dimethylanilinium sulfates

Three dimethylanilinium sulfates (DMAS) have been prepared and characterised by elemental and spectral studies. Thermal decomposition of these salts has been studied by TG and simultaneous TG-DTG technique and kinetic parameters were evaluated from both dynamic and isothermal TG data using mechanism based kinetic equations. The thermal decomposition pathways have also been suggested and it has been found that DMAS salts give dimethyl aminobenzenesulfonic acids (DMABSA) via solid state reaction. The primary step in the thermal decomposition involves proton transfer followed by sulfonation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Separation and gravimetric determination of cerium and lanthanum with N-m-tolyl-m-nitrobenzohydroxamic acid

Cerium and lanthanum were determined gravimetrically by selective precipitation with N-m-tolyl-m-nitrobenzohydroxamic acid and separated from several metal ions such as Ag(+), Be(2+) , Pb(2+) , Mn(2+) , Cu(2+), Zn(2+) , Cd(2+) , Hg(2+) , Pd(2+) , Ga(3+) A1(3+) , Bi(3+) , Sb(3+), Sn(4+), Ce(3+) , Pr(3+) , Nd(3+) , Ti(4+), Zr(4+), Th(4+), V(5+) , Mo(6+) and U(6+) . The precipitates were weighted directly after drying at 110 degrees . The analytical results indicated the composition of the complexes to be (C(14)H(11)N(2)O(4))(n)M.     

Phosphorescent κ3-(N^C^C)-Gold(III) Complexes: Synthesis,Photophysics, Computational Studies and Application to Solution-Processable OLEDs

Efficient OLED devices have been fabricated using organometallic complexes of platinum group metals. Still, the high material cost and low stability represent central challenges for their application in commercial display technologies. Based on its innate stability, gold(III) complexes are emerging as promising candidates for high-performance OLEDs. Here, a series of alkynyl-, N-heterocyclic carbene (NHC)- and aryl-gold(III) complexes stabilized by a κ³-(N^C^C) template have been prepared and their photophysical properties have been characterized in detail. These compounds exhibit good photoluminescence quantum efficiency (η_PL) of up to 33 %. The PL emission can be tuned from sky-blue to yellowish green colors by variations on both the ancillary ligands as well as on the pincer template. Further, solution-processable OLED devices based on some of these complexes display remarkable emissive properties (η_CE 46.6 cd.A⁻¹ and η_ext 14.0 %), thus showcasing the potential of these motifs for the low-cost fabrication of display and illumination technologies.     

A review on environmental applications of chitosan biopolymeric hydrogel based composites

Abstract

Chitosan (CS) is being used for fabrication of low cost, biocompatible materials that have applicability in fields such as agriculture, biotechnology and environment. In Environmental research, one of the applications of CS based hydrogel composites are in form of biosorbents for eviction of toxic dyes, heavy metals and nutrients from effluent streams. The adsorption potential could be attributed to the reactive functional groups existing on the surface of CS. CS based materials can also be employed for oil/water separation, as a fertilizer carrier, in Microbial fuel cells as Electrolyte membrane and as Electrochemical/Biosensors for detecting and analyzing few environmental pollutants such as pesticides. The earlier review papers on the subject matter have concentrated mainly on dye and heavy metal removal without giving details of its utility in the field of electrochemistry and agriculture. Though the biopolymer holds numerous applications, it has not been discussed extensively. Thus, an attempt has been made to elucidate the current and potential applications of CS hydrogels and composites based on the efficacy it has shown in areas of removal of organic and inorganic contaminants such as dyes, heavy metals and nutrients, in agriculture, oil and water separation, Microbial Fuel cells and Electrochemical/Biosensors.

• HIGHLIGHTS

• Chitosan based hydrogel composites could be extensively used in the field of Environment Technology.

• The composites act as effective biosorbents for dye, heavy metal and nutrient removal because of the functional groups present on Chitosan’s surface.

• These can also be effectively used for oil/water separation and also as a fertilizer/pesticide carrier for their slow release.

• Chitosan based electrolytes can become a promising ecofriendly substitute for synthetic polymers in fuel cells.

• These biopolymers have also been researched upon as electrochemical/biosensors in recent years for detecting environmental pollutants.

     

Immobilization of Pd Catalysts on Mesoporous Silica for Amine- and Copper-Free Sonogashira Coupling Reactions

Immobilization of catalysts on solid supports is a promising approach to combine the advantages of heterogeneous and homogeneous catalysts. Pd(PPh₃)₂Cl₂, known as an extremely active homogeneous catalyst for the Sonogashira coupling reaction, has been immobilized on high-surface-area MCF (mesocellular foams)–type mesoporous silica powder modified with 3-aminopropyltriethoxysilane and subsequently with diphenylphosphine. The functionalized MCF-type silica and supported catalysts have been characterized by x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), elemental analysis, nitrogen sorption porosimetry, and scanning electron microscopy (SEM). Such supported Pd catalysts have proven to be useful recyclable reagents for copper- and amine-free Sonogashira coupling reactions of haloaromatic compounds with terminal alkynes.     

Hidden chemistry of substituted aniline radical cations in water: a mechanistic study

Absolute rate constants for hydroxyl radical, azide radical, and hydrated electron reactions with a sulfa drug 4,4'‐diamino diphenyl sulfone (dapsone) in water have been evaluated using electron pulse radiolysis technique. Absolute rate constants for hydroxyl radical and azide radical were determined as (8.4 ± 0.3) × 10⁹ and (5.6 ± 0.5) × 10⁹ M^?1 s^?1, respectively. The reduction of dapsone with the hydrated electron occurred with rate constant of (9.2 ± 0.1) × 10⁹ M^?1 s^?1. Hydroxyl radical reactions result in the synchronous formation of adduct as well as anilino radical. The interesting observation is that the yield of the anilino radical increases with increase in pH. Contrary to this, the yield of the adduct decreases with pH. We propose that hydroxyl radical adds predominantly to the aniline. In contrast, the reaction of azide radical with the dapsone suggests that the reaction occurs at the –NH₂ moiety of the aniline ring. The free radical electron transfer from dapsone to parent radical cation of non‐polar solvent also results in the formation of anilino radical only suggesting that the radical cation of dapsone has a short lifetime. The reaction of hydrated electrons with the dapsone suggests that the reaction occurs at different reaction site. The experimental results supported by theoretical calculations of this study provide fundamental mechanistic parameters that probably decide the fate of the radical cation of aniline derivatives. Copyright © 2014 John Wiley & Sons, Ltd.