oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Enantiomeric Separation and Determination of the Enantiomeric Impurity of Armodafinil by Capillary Electrophoresis with Sulfobutyl Ether-β-cyclodextrin as Chiral Selector  [PDF]
Wei Wang,Suyun Xiang,Xiaojuan Zhou,Yibing Ji,Bingren Xiang
Molecules , 2012, DOI: 10.3390/molecules17010303
Abstract: A selective capillary electrophoresis method using sulfobutyl ether-β-cyclodextrin as a chiral selector was developed and validated for the determination of the enantiomeric impurity of (R)-modafinil, i.e., armodafinil. Several parameters were optimized for a satisfactory enantioresolution, including the type and concentration of chiral selector and organic modifier, pH of background electrolyte (BGE), capillary temperature. The finally adopted condition was: 20 mmol/L phosphate buffer at pH 7.5, containing 20 mmol/L sulfobutyl ether-β-cyclodextrin and 20% methanol, at temperature of 25 °C. A good resolution of 3.3 for the two enantiomers of modafinil was achieved by applying the optimal conditions. The limit of detection (LOD) and limit of quantification (LOQ) of (S)-modafinil were 1.25 μg/mL and 2.50 μg/mL, respectively. The established method was also proven to display good selectivity, repeatability, linearity and accuracy. Finally, the method was used to investigate the enantiomeric purity of armodafinil in bulk samples.
Enantiomeric Separation of N-FMOC Amino Acids with Sulfobutyl Ether-β-Cyclodextrin as Chiral Additive by Capillary Electrokinetic Chromatography
毛细管电动色谱带电环糊精拆分N-FMOC氨基酸对映体

RUAN Zong-qin,LI Ju-bai,LU Hao-jie,OU Qing-yu,
阮宗琴
,李菊白,陆豪杰,欧庆瑜

色谱 , 2000,
Abstract: Enantiomeric separation of N-FMOC amino acids by capillary electrophoresis with an anionic chiral resolving agent, sulfobutyl ether-beta-cyclodextrin (SBE-beta-CD) with average substitution degree of 3.8, employed as chiral additive was studied. Chiral separation was achieved with the mode of electrokinetic chromatography due to the electrophoretic mobility and chiral complexing ability of the chiral additive. The effects of pH of background electrolyte, the concentration of sulfobutyl ether-beta-cyclodextrin on enantiomeric separations were investigated. The enantiomeric separations of 8 N-FMOC amino acids were accomplished, among which 5 N-FMOC amino acids could be on baseline separated.
A SILVER(I) PVC-MEMBRANE SENSOR BASED ON SYNTHESIZED DILAKTAM CROWN ETHER
MASROURNIA,MAHBOBEH; ALI ZAMANI,HASSAN; MOHAMADZADEH,HANIYEH; MOHAMMAD SEYEDI,SEYED; REZA GANJALI,MOHAMMAD; ESHGHI,HOSSEIN;
Journal of the Chilean Chemical Society , 2009, DOI: 10.4067/S0717-97072009000100015
Abstract: in this work, we introduce a highly selective and sensitive silver(i) pvc-membrane sensor. dilaktam crown ether (dlce) was used as a membrane-active component to prepare a highly sensitive ag(i)-selective polymeric membrane electrode. this sensor illustrated very good selectivity and sensitivity towards silver ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. the sensor exhibited a nernstian behavior (with a slope of 59.8 ± 0.2 mv per decade) for a concentration range (1.0 x 10-5-1.0 x 101 m) with a detection limit of 6.8xl0-6 m. it displayed a response time in the whole concentration range (~20 s) and its usage exceeded a 75 days period in the ph range of 5.1-7.2. the proposed electrode application was found to be successful as an indicator electrode in the titration with nacl.
A SILVER(I) PVC-MEMBRANE SENSOR BASED ON SYNTHESIZED DILAKTAM CROWN ETHER  [cached]
MAHBOBEH MASROURNIA,HASSAN ALI ZAMANI,HANIYEH MOHAMADZADEH,SEYED MOHAMMAD SEYEDI
Journal of the Chilean Chemical Society , 2009,
Abstract: In this work, we introduce a highly selective and sensitive silver(I) PVC-membrane sensor. Dilaktam Crown ether (DLCE) was used as a membrane-active component to prepare a highly sensitive Ag(I)-selective polymeric membrane electrode. This sensor illustrated very good selectivity and sensitivity towards silver ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The sensor exhibited a Nernstian behavior (with a slope of 59.8 ± 0.2 mV per decade) for a concentration range (1.0 x 10-5-1.0 x 101 M) with a detection limit of 6.8xl0-6 M. It displayed a response time in the whole concentration range (~20 s) and its usage exceeded a 75 days period in the pH range of 5.1-7.2. The proposed electrode application was found to be successful as an indicator electrode in the titration with NaCl.
Inclusion Complexes of Sunscreen Agents with β-Cyclodextrin: Spectroscopic and Molecular Modeling Studies  [PDF]
Nathir A. F. Al-Rawashdeh,Khaled S. Al-Sadeh,Mohammad Bassam Al-Bitar
Journal of Spectroscopy , 2013, DOI: 10.1155/2013/841409
Abstract: The inclusion complexes of selected sunscreen agents, namely, oxybenzone (Oxy), octocrylene (Oct), and ethylhexyl-methoxycinnamate (Cin) with β-cyclodextrin (β-CD) were studied by UV-Vis spectroscopy, differential scanning calorimetry (DSC), 13C NMR techniques, and molecular mechanics (MM) calculations and modeling. Molecular modeling (MM) study of the entire process of the formation of 1?:?1 stoichiometry sunscreen agent/β-cyclodextrin structures has been used to contribute to the understanding and rationalization of the experimental results. Molecular mechanics calculations, together with 13C NMR measurements, for the complex with β-CD have been used to describe details of the structural, energetic, and dynamic features of host-guest complex. Accurate structures of CD inclusion complexes have been derived from molecular mechanics (MM) calculations and modeling. The photodegradation reaction of the sunscreen agents' molecules in lotion was explored using UV-Vis spectroscopy. It has been demonstrated that the photostability of these selected sunscreen agents has been enhanced upon forming inclusion complexes with β-CD in lotion. The results of this study demonstrate that β-CD can be utilized as photostabilizer additive for enhancing the photostability of the selected sunscreen agents' molecules. 1. Introduction Cyclodextrins (CDs) are cyclic oligosaccharides composed of glucopyranose units linked together by oxygen bridges at the 1 and 4 positions (α,1,4-glycoside bonds) [1]. This class of organized media possesses a hydrophilic exterior and a hydrophobic cavity due to C3H, C5H, and C6H hydrogens and O4 ether oxygen which enables the CDs to extract a variety of organic guest molecules of appropriate size and hydrophobicity from the bulk aqueous solution [2–4]. The most familiar members are α-, β-, and γ-CDs consisting of six, seven, and eight glucose units, respectively. Complexation of various compounds with CDs leads to an enhancement in some of the characteristics of the guest molecules, such as thermalstability and photostability, bioavailability, membrane permeability, and solubility [5]. Thus, CDs and their derivatives have been employed in a variety of fields such as catalysis, electrochemical analysis, pharmaceutical and food industries [6–12], separation sciences [13–18], and biotechnology [19, 20]. In cosmetics the use of CDs is still having a shortage in the literature information in comparison with other areas, whereas most publications are patents. It is noteworthy to mention that significant alterations in the physicochemical properties of
Thymoquinone β-Cyclodextrin Nanoparticles System: A Preliminary Study
T. Cardoso,C. I. C. Galhano,M. F. Ferreira Marques,A. Moreira da Silva
Spectroscopy: An International Journal , 2012, DOI: 10.1155/2012/902486
Abstract: Thymoquinone is a natural product, the main constituent of Nigella sativa seeds, which exhibits anti-inflammatory and anticancer activities. Among several existing molecules capable of forming an inclusion compound structure, cyclodextrins are applied in the pharmaceutical industry either to increase solubility of hydrophobic molecules or to protect molecules from inactivation or degradation. β-Cyclodextrin is currently the most common cyclodextrin in pharmaceutical formulations and probably the best studied in humans. In order to study the properties of inclusion compounds based on cyclodextrins and thymoquinone Fourier Transform Infrared (FTIR), Ultraviolet-Visible, Positron Annihilation Lifetime (PAL) Spectroscopies and calorimetric studies by Differential Scanning Calorimetry (DSC) were used. The obtained results indicate the formation of a 1 : 1 inclusion compound between cyclodextrin and thymoquinone. PALS and DSC measurements also provided evidence of the inclusion compound's activity.
Graded/Gradient Porous Biomaterials  [PDF]
Xigeng Miao,Dan Sun
Materials , 2010, DOI: 10.3390/ma3010026
Abstract: Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.
Adhesive Bonding to Dentin Improved by Polymerizable Cyclodextrin Derivatives
Bowen, Rafael L.,Schumacher, Gary E.,Giuseppetti, Anthony A.
Journal of Research of the National Institute of Standards and Technology , 2009,
Abstract: The objective of this work was to determine bonding characteristics of a hydrophilic monomer formulation containing polymerizable cyclodextrin derivatives. The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and cyclodextrins with functional groups attached by hydrolytically stable ether linkages could form strong adhesive bonds to dentin. The previously synthesized polymerizable cyclodextrin derivatives were formulated with sorbitol dimethacrylate, methacrylic acid and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The same formulation without the polymerizable cyclodextrin derivatives isolated the effects of the polymerizable cyclodextrin derivatives. A commercial self-etching bonding system was tested as a comparative control. Ground mid-coronal dentin was etched with 37 % phosphoric acid (H3PO4) for 15 s and rinsed with distilled water for 10 s. Formulations were applied to the moist dentin and light-cured 10 s. A packable composite was then applied through irises and light-cured 60 s. Teeth were stored in water for 24 h before bonds were tested in a shearing orientation. One-way ANOVA was performed on the data. The average values of shear bond strengths were defined as loads at fracture divided by the 4 mm diameter iris areas. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was higher (p < 0.05), where p is a fraction of the probability distribution) than that of the same monomeric formulation except that the polymerizable cyclodextrin derivatives were not included. This was supporting evidence that the polymerizable cyclodextrin derivatives contributed to improved bonding. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was also higher (p < 0.05) than that of the commercial self-etching bonding system. These preliminary results are in accordance with the hypothesis that formulations containing polymerizable cyclodextrin derivatives can form strong adhesive bonds to hydrated dentin surfaces. Further improvements in bonding to hydrated biological tissues by use of advanced formulations are anticipated.
Classification of Biomaterials used in Medicine  [cached]
Patitapabana Parida,Ajit Behera,Subash Chandra Mishra
International Journal of Advances in Applied Sciences , 2012, DOI: 10.11591/ijaas.v1i3.882
Abstract: In this decade many researches are potentially going forward by using biomaterials in the medical field. Biomaterials can used in living creature body, taking in account of there biocompatibility. This paper describes about classification of different biomaterials which are used in medical industries. Advances in surgical technique and instruments have permitted materials to be used in ways that were not possible previously. Bio-material can partially/totally replaces one or more part of the body. Before using biomaterials, it should in mind that, which categories they are belongs and main focuses are on biocompatibility, bioinert, bioactive/surface reactive, biodegradable, sterilizability, adequate mechanical and physical properties, manufacturability, low weight, reasonable cost etc. It is necessary to classify biomaterials for there suitable use in medical industries.
Applications of Biomaterials to Liquid Crystals  [PDF]
Kazuki Iwabata,Urara Sugai,Yasutaka Seki,Hirokazu Furue,Kengo Sakaguchi
Molecules , 2013, DOI: 10.3390/molecules18044703
Abstract: Nowadays, chemically synthesized proteins and peptides are attractive building blocks and have potential in many important applications as biomaterials. In this review, applications of biomaterials to thermotropic liquid crystals are discussed. The review covers the improvement of the performance of liquid crystal displays using liquid crystal physical gels consisting of a liquid crystal and amino acid-based gelators, and also new functionalization of liquid crystals. Moreover, the influence of DNA, which is one of the more attractive biomaterials, dispersed in thermotropic liquid crystals and its potential use in the liquid crystal industry is described. In addition, we found interesting results during electrooptical measurements of liquid crystals doped with DNA, and explain them from the point of view of biological applications. These recent approaches suggest that these biomaterials may be applicable in the electronic device industry and should be considered as an interesting material with their physical properties having the potential to create or refine an industrial product.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.