Exciton line broadening in strained InGaAs/GaAs single quantum wells

We report the first observation of well-resolved exciton peaks in the room-temperature absorption spectrum of the strained In_0.20Ga_0.80As/GaAs Single Quantum-Well (SQW) structure. The best fit of the exciton resonances gives the conduction-band offset ratioQ _c=0.70±0.05. The strength of the exciton-phonon coupling is determined from linewidth analysis and is found to be much larger than that of strained InGaAs/GaAs MQW structures.     

Filamentous bacteriophage stability in non-aqueous media.

BACKGROUND: Filamentous bacteriophage are used as general cloning vectors as well as phage display vectors in order to study ligand-receptor interactions. Exposure to biphasic chloroform-water interface leads to specific contraction of phage, to non-infective I- or S-forms. RESULTS: Upon exposure, phage were inactivated (non-infective) at methanol, ethanol and 1-propanol concentrations inversely dependent upon alcohol hydrophobicity. Infectivity loss of phage at certain concentrations of 1-propanol or ethanol coincided with changes in the spectral properties of the f1 virion in ultraviolet fluorescence and circular dichroism studies. CONCLUSIONS: The alcohols inactivate filamentous phage by a general mechanism--solvation of coat protein--thereby disrupting the capsid in a manner quite different from the previously reported I- and S-forms. The infectivity retention of phagemid pG8H6 in 99% acetonitrile and the relatively high general solvent resistance of the phage strains studied here open up the possibility of employing phage display in non-aqueous media.     

Modulating the acidity: highly acidic Brønsted acids in asymmetric catalysis

Recently, chiral highly acidic Brønsted acids have emerged as powerful catalysts for enantioselective C C and C X bond‐forming reactions. Their strong acidity renders them valuable tools for the activation of imines, carbonyl compounds, and other weakly basic substrates. As a result, new perspectives are opened and highly stereoselective transformations based on the concept of chiral contact‐ion‐pair catalysis can be realized. This Minireview gives an overview of the design and application of these new organocatalysts and presents recent results in this rapidly growing field.     

Supermacroporous cryogel matrix for integrated protein isolation. Immobilized metal affinity chromatographic purification of urokinase from cell culture broth of a human kidney cell line

A new type of supermacroporous, monolithic, cryogel affinity adsorbent was developed, allowing the specific capture of urokinase from conditioned media of human fibrosarcoma cell line HT1080. The affinity adsorbent was designed with the objective of using it as a capture column in an integrated perfusion/protein separation bioreactor setup. A comparative study between the utility of this novel cryogel based matrix and the conventional Sepharose based affinity matrix for the continuous capture of urokinase in an integrated bioreactor system was performed. Cu(II)-ion was coupled to epoxy activated polyacrylamide cryogel and Sepharose using iminodiacetic acid (IDA) as the chelating ligand. About 27-fold purification of urokinase from the conditioned culture media was achieved with Cu(II)-IDA-polyacrylamide cryogel column giving specific activity of about 814 Plough units (PU)/mg protein and enzyme yields of about 80%. High yields (95%) were obtained with Cu(II)-IDA-Sepharose column by virtue of its high binding capacity. However, the adsorbent showed lower selectivity as compared to cryogel matrix giving specific activity of 161 PU/mg protein and purification factor of 5.3. The high porosity, selectivity and reasonably good binding capacity of Cu(II)-IDA-polyacrylamide cryogel column make it a promising option for use as a protein capture column in integrated perfusion/separation processes. The urokinase peak pool from Cu(II)-IDA-polyacrylamide cryogel column could be further resolved into separate fractions for high and low molecular weight forms of urokinase by gel filtration chromatography on Sephacryl S-200. The selectivity of the cryogel based IMAC matrix for urokinase was found to be higher as compared to that of Cu(II)-IDA-Sepharose column.     

On the tangential touch between the free and the fixed boundaries for the two-phase obstacle-like problem

In this paper we consider the following two-phase obstacle-problem-like equation in the unit half-ball

Neutron powder diffraction investigations of hydrogenated Pd3P0.80 and Pd6P

The solid solutions Sr_3?xLa_xMn₂O₇ (0 ≤ x ≤ 1.50) and Sr_3?xLn_xMn₂O₇ (Ln = Nd, Sm, Gd; 0 ≤ x ≤ 1.40) with Sr₃Ti₂O₇-type structure have been prepared. Their cell parameters and $\text{c}\text{a}$ ratios are related to the size of the rare earths and to the Mn³⁺ ion concentration.