Heavy metal removal by biosorption using Phanerochaete chrysosporium

Biosorption using microbial cells as adsorbents is being seen as a cost-effective method for the removal of heavy metals from wastewaters. Biosorption studies with Phanerochaete chrysosporium were performed for copper (II), lead (II), and cadmium (II) to evaluate the effectiveness and to optimize the operational parameters using response surface methodology. The operational parameters chosen were initial metal ion concentration, pH, and biosorbent dosage. Using this method, the metal removal could be correlated to the operational parameters, and their values were optimized. The results showed fairly high adsorptive capacities for all the metals within the settings of the operational parameters. The removal efficiencies followed the order Pb>Cu>Cd. As a general trend, metal removal efficiency decreased as the initial metal ion concentration increased, and the results fitted the Langmuir and Freundlich isotherms well.     

Structural,optical, electrical and luminescence properties of electron beam evaporated CdSe:In films

CdSe:In films were prepared by electron beam evaporation technique using CdSe and In₂Se₃ (purity ∼99.9%) pellets. The crystal structure of the films with and without Indium, measured by X‐ray diffraction (XRD), showed a typical wurtzite structure, higher Indium doping shifts the peak angle to higher side along with the broadening of the peaks. X‐ray photoelectron spectroscopy (XPS) studies indicated binding energies corresponding to 54 eV (Se3d_5/2), 444 eV (In 3d_5/2), 411 eV (Cd 3d_3/2), (Cd 3d_5/2). Atomic force microscope (AFM) studies indicated a uniform surface.The grain size decreases with increase of In doping. A decrease in the band gap was observed with increase of dopant concentration. Resistivity of the films is in the range of 10^‐3 Ωcm. Carrier density was in the range of 10²¹ cm^‐3 for the films. The photolumineasenec spectra (PL) spectra indicated three peaks. The peak intensity decreases as the Indium concentration increases. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On nonsingular regular magic squares of odd order

Using centroskew matrices, we provide a necessary and sufficient condition for a regular magic square to be nonsingular. Using latin squares and circulant matrices we describe a method of construction of nonsingular regular magic squares of order n where n is an odd prime power.     

Stable Functions and Extension of Vietoris’ Theorem

In this work, using subordination results for the Cesáro sum of certain analytic functions, a concept called Cesáro stable is given and two conjectures in this direction are also proposed. Using an extension of Vietoris’ theorem on positivity of cosine sums, some results on positivity of cosine and sine sums are obtained. These results are useful in discussing some particular cases of the proposed conjectures.     

Excited state proton transfer kinetics of 4-hydroxydiphenyl ether

Fluorimetric titrations of 4-hydroxydiphenyl ether and its anion give stretched sigmoid curves with two inflection points. This reveals that the rates of excited state proton exchange are comparable to the rates of deactivation of the conjugate pair. These curves are analyzed using the lifetimes of the species. The excited state equilibrium constants determined from rate constants and by other methods are compared. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 861–867, 1997     

Employing the fluorescence anisotropy and quenching kinetics of tryptophan to hunt for residual structures in denatured proteins

Residual structures in denatured proteins have acquired importance in recent years owing to their role as protein-folding initiation sites. Locating these structures in proteins has proved quite formidable, requiring techniques like NMR. Here in this report, we take advantage of the ubiquitous presence of tryptophan residues in residual structures to hunt for their presence using steady-state fluorescence spectroscopy. The surface accessibility and rotational dynamics of tryptophan in putative residual structures among ten different proteins, namely glucagon, melittin, subtilisin carlsberg, myelin basic protein, ribonuclease T₁, human serum albumin, barstar mutant, bovine serum albumin, lysozyme and Trp-Met-Asp-Phe-NH₂ peptide, was studied using steady state fluorescence quenching and anisotropy, respectively. Five proteins, namely ribonuclease T₁, bovine serum albumin, melittin, barstar and hen egg white lysozyme appear likely to possess tryptophan(s) in hydrophobic clusters based on their reduced bimolecular quenching rates and higher steady-state anisotropy in proportion to their chain length. We also show that the fluorescence emission maximum of tryptophan is insensitive to the presence of residual structures.     

Anionic Polymerization of Z,Z-2,4Hexadienedinitrile

Abstract

Z,Z-2,4-Hexadienedinitrile, synthesized by the oxidative cleavage of o-phenylenediamine, was found to undergo anionic polymerization with n-BuLi in DMF at room temperature or below. The polymerization behavior appears to be similar to that of acrylonitrile polymerization using n-BuLi as initiator. Infrared and NMR analysis of the polymer indicate the presence of both 1,4 and 1,2 linkages, with the latter predominating.     

Proline-catalysed asymmetric ketol cyclizations: The template mechanism revisited

A modified template mechanism based on modelling studies of energy minimised complexes is presented for the asymmetric proline-catalysed cyclization of triketones1,2 and3 to the 2S,3S-ketols1a,2a and3a respectively. The template model involves a three-point contact as favoured in enzyme-substrate interactions. Our minimisation studies are in agreement with the divergent behaviour of the 6,5-, 6,6-and 6,7-bicyclic systems. They support the high 93.4%ee observed with the 6,5-bicyclic ketol and the lower 73%ee found with the 6,6-bicyclic ketol. The calculations also explain the lack of asymmetric induction with the 6,7-bicyclic system