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Improved Selectivity (improved + selectivity)
Selected AbstractsNovel Anion Exchangers for Electrodes with Improved Selectivity to Divalent AnionsELECTROANALYSIS, Issue 17 2004Vladimir Egorov Abstract It has been found that replacing of several long-chain alkyl substituents at the nitrogen atom of lipophilic quaternary ammonium salts (QAS) by methyls results in a dramatic increase of the potentiometric selectivity of ion-selective electrodes (ISE) with QAS-based plasticized PVC membranes to some divalent anions against the monovalent ones. The discussed effect of QAS cation nature on the potentiometric selectivity is also partly retained for ISE with neutral carrier-based membranes doped with QAS to provide anion permselectivity. This opens up new possibilities to control the potentiometric selectivity of ISE for divalent anions by the appropriate selection of the anion exchanger. [source] Fuel Cells, Advanced Reactors and Smart Catalysis: The Exploitation of Ceramic Ion-Conducting MembranesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2003I.S. Metcalfe Abstract Membrane reactors are of great interest in the chemical industries because they offer the possibility of improved yields, improved selectivities and more compact plant. However, a significant barrier to their uptake is the unavailability of membrane systems having the required performance at an acceptable cost. In this paper we will explore the use of one class of membrane that has the potential to deliver high performance at reasonable cost. Ion-conducting ceramic membranes can be used in a wide range of high temperature applications including fuel cells, advanced reactors and even smart catalytic systems. [source] Enhancement of ultrafiltration using gas sparging: a comparison of different membrane modules,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2-3 2003Zhanfeng Cui Abstract Ultrafiltration is widely used in the chemical, pharmaceutical, food and water industries. Practical difficulties arise in designing and operating the process due to concentration polarisation and membrane fouling. Enhancement of ultrafiltration is highly desirable to achieve a higher permeate flux at a fixed energy input, or a reduced energy input whilst maintaining the level of permeate flux, or an improved selectivity of the membrane. One effective, simple, and economic technique used to enhance ultrafiltration is the use of gas bubbles, ie injecting gas into the feed stream to create a gas,liquid two-phase cross-flow operation. In this paper, an attempt is made to compare the effect of ,bubbling' on the ultrafiltration performance, using different membrane modules (in particular, tubular and hollow fibre membrane modules). The difference in performance can be related to the feature of two-phase flow hydrodynamics and its respective effect on mass transfer. The advantages and drawbacks of using this technique to enhance ultrafiltration are discussed. © 2003 Society of Chemical Industry [source] The evolution of progesterone receptor ligandsMEDICINAL RESEARCH REVIEWS, Issue 3 2007Kevin P. Madauss Abstract Progesterone is one of the first nuclear receptor hormones to be described functionally and subsequently approached as a drug target. Because progesterone (1) affects both menstruation and gestation via the progesterone receptor (PR), research aimed at modulating its activity is usually surrounded by controversy. However, ligands for PR were developed into drugs, and their evolution can be crudely divided into three periods: (1) drug-like steroids that mimic the gestational properties of progesterone; (2) drug-like steroids with different properties from progesterone and expanded therapeutic applications; and (3) non-steroidal PR ligands with improved selectivity and modulator properties and further expanded therapeutic applications. Although the latter have yet to see widespread clinical applications, their development is founded on a half century of research, and they represent the future for this drug target. © 2006 Wiley Periodicals, Inc. Med Res Rev, 27, No. 3, 374,400, 2007 [source] Phosphodiesterase 5 (PDE 5) inhibitors for the treatment of male erectile disorder: Attaining selectivity versus PDE6MEDICINAL RESEARCH REVIEWS, Issue 3 2006Dmitri Pissarnitski Abstract The role of phosphodiesterase type 5 (PDE5) in the mechanism of male erection has been well understood, and several drugs inhibiting this enzyme are being used for the treatment of erectile dysfunction (ED). Discovery of inhibitors with improved selectivity versus other PDE isozymes could lead to drugs with improved safety profile. Achievement of selectivity versus PDE6, co-inhibition of which results in disturbances of color perception, remains the most challenging aspect of current drug discovery programs. The present review describes several case studies, where significant (>100 fold) selectivity versus PDE6 has been attained via investigation of structure,activity relationships (SAR). Special attention is given to the chemical routes leading to novel chemotypes and allowing efficient exploration of their SAR's. Strategies for attaining inhibitor selectivity discussed below may be applicable for other drug discovery programs. © 2005 Wiley Periodicals, Inc. Med Res Rev [source] Antibodies and Genetically Engineered Related Molecules: Production and PurificationBIOTECHNOLOGY PROGRESS, Issue 3 2004A. Cecília A. Roque Antibodies and antibody derivatives constitute 20 % of biopharmaceutical products currently in development, and despite early failures of murine products, chimeric and humanized monoclonal antibodies are now viable therapeutics. A number of genetically engineered antibody constructions have emerged, including molecular hybrids or chimeras that can deliver a powerful toxin to a target such as a tumor cell. However, the general use in clinical practice of antibody therapeutics is dependent not only on the availability of products with required efficacy but also on the costs of therapy. As a rule, a significant percentage (50,80%) of the total manufacturing cost of a therapeutic antibody is incurred during downstream processing. The critical challenges posed by the production of novel antibody therapeutics include improving process economics and efficiency, to reduce costs, and fulfilling increasingly demanding quality criteria for Food and Drug Administration (FDA) approval. It is anticipated that novel affinity-based separations will emerge from the development of synthetic ligands tailored to specific biotechnological needs. These synthetic affinity ligands include peptides obtained by synthesis and screening of peptide combinatorial libraries and artificial non-peptidic ligands generated by a de novo process design and synthesis. The exceptional stability, improved selectivity, and low cost of these ligands can lead to more efficient, less expensive, and safer procedures for antibody purification at manufacturing scales. This review aims to highlight the current trends in the design and construction of genetically engineered antibodies and related molecules, the recombinant systems used for their production, and the development of novel affinity-based strategies for antibody recovery and purification. [source] | ||||||||||