Search results for "liquid"
showing 10 items of 4351 documents
O-Ribosyl-phosphate purine as a constant modified nucleotide located at position 64 in cytoplasmic initiator tRNAsMetof yeasts
1991
The unknown modified nucleotide G*, isolated from both Schizosaccharomyces pombe and Torulopsis utilis initiator tRNAs(Met), has been identified as an O-ribosyl-(1"----2')-guanosine-5"-phosphate, called Gr(p), by means of HPLC, UV-absorption, mass spectrometry and periodate oxidation procedures. By comparison with the previously published structure of Ar(p) isolated from Saccharomyces cerevisiae initiator tRNA(Met), the (1"----2')-glycosidic bond in Gr(p) has been postulated to have a beta-spatial conformation. The modified nucleotide Gr(p) is located at position 64 in the tRNA(Met) molecules, i.e. at the same position as Ar(p). Since we have also characterized Gr(p) in Candida albicans ini…
Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester
2011
Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester Hantzsch ester synthesis was investigated using (2-hydroxyethyl)-ammonium carboxylates, polar and hydrophilic ionic liquids possessing low toxicity and high biodegradability. The reaction rates and yields of the products in ionic liquids were greater than those in common organic solvents. The relationship between the structure of the ionic liquid used and the structure of the heterocyclic compound was investigated.
Classification of vegetable oils according to their botanical origin using amino acid profiles established by High Performance Liquid Chromatography …
2010
Abstract A preliminary study using amino acid profiles to classify oils according to their botanical origin has been performed. Amino acid profiles were obtained from hydrolysis of proteins present in vegetable oils, and established by High Performance Liquid Chromatography (HPLC) with UV–vis detection. Proteins present in hazelnut, corn, soybean, olive, avocado, peanut and grapeseed oils were precipitated with acetone, and the residue was hydrolysed in acid medium. The amino acids obtained were derivatized with o -phthaldialdehyde and separated by HPLC. Peaks corresponding to 18 amino acids were observed using a C18 column and a gradient of acetonitrile–water in the presence of a 5 mM citr…
Single-pump heart-cutting two-dimensional liquid chromatography applied to the determination of fatty alcohol ethoxylates.
2014
Abstract A setup for heart-cutting bi-dimensional liquid chromatography (LC–LC), constructed with a chromatograph provided with a single pump, an auxiliary 6-port 2-position valve (V 6/2 ) and a column selector valve (V CS ), is described. The possible ways of connecting the two valves for LC–LC, namely with V 6/2 first followed by V CS and vice versa, are compared. The possibility of using the setups for preconcentration followed by the backwards transfer of the preconcentrated solutes to the detector or to a second column is also shown. The V 6/2 -first configuration for LC–LC was applied to the characterization of industrial fatty alcohol ethoxylates (FAEs) using UV–vis detection. For th…
Semicarbazides as gel forming agents for common solvents and liquid crystals
2006
This paper describes the synthesis of 14 new gelling agents with semicarbazide groups as H-bonding motifs and alkyl- and/or azobenzene side groups. They gel solvents like decaline, 1,2-dichlorobenzene and toluene and liquid crystalline mixtures. X-Ray structure analysis shows that the semicarbazides are connected by H-bonds, each molecule to four neighbours. As a result a ribbon is formed with a core of H-bonded semicarbazide groups and alkyl chains sticking to the side. IR measurements show an unchanged H-bonding motif in large crystals and in the gel fibres, even in LC-mixture. During heating the gel melts (rheology), while the H-bonding motif of the crystal disappears (IR and DSC measure…
On the calculation of free energy of mixing for aqueous polymer solutions with group-contribution models
2010
Abstract Liquid–liquid phase separation processes are currently used as a route to prepare polymeric porous structures for various applications (membranes and scaffolds for tissue engineering). In membrane and foam fabrication technologies, binary and mainly ternary polymer solutions are used. Membrane morphology is strongly affected by phase equilibria of processing solution. In order to achieve a better control of membrane morphology and to explore a wide quantity of solvents, a predictive tool addressing experimentals would be strongly advisable. In this paper, group contribution models were chosen to test the applicability on a PLLA–dioxane–water ternary polymer solution, whose experime…
FT-IR and dielectric study of water/AOT liquid crystals
2000
Abstract In order to explore the influence of microwave radiation on highly viscous microheterogeneous systems, the evolution of structural and dynamical properties of the water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) liquid crystals as a function of the molar ratio R (R=[water]/[AOT]) has been investigated by FT-IR spectroscopy and time domain reflectometry. The study emphasises how the progressive hydration of the surfactant head groups is mainly responsible for the structural and dynamical evolution of water/AOT liquid crystals. In particular, it has been found that the state of water at lower R values is strongly perturbed, bulk-like water appears only at R>23 and the water/AOT in…
Liquid-crystalline ordering as a concept in materials science: from semiconductors to stimuli-responsive devices.
2013
While the unique optical properties of liquid crystals (LCs) are already well exploited for flat-panel displays, their intrinsic ability to self-organize into ordered mesophases, which are intermediate states between crystal and liquid, gives rise to a broad variety of additional applications. The high degree of molecular order, the possibility for large scale orientation, and the structural motif of the aromatic subunits recommend liquid-crystalline materials as organic semiconductors, which are solvent-processable and can easily be deposited on a substrate. The anisotropy of liquid crystals can further cause a stimuli-responsive macroscopic shape change of cross-linked polymer networks, w…
Carbon-based ionic liquid gels: alternative adsorbents for pharmaceutically active compounds in wastewater
2021
With the aim of obtaining adsorbent systems to be used for the removal of pharmaceutically active compounds (PhACs) from wastewater, some hybrid ionic liquid gels (HILGs) were obtained from the combination of ionic liquid-based supramolecular gels and carbon materials, like graphite, graphene and graphene oxide (graphene OX). The properties of HILGs were investigated by determining their gel–sol transition temperature and rheological features. They were tested for the removal of PhACs belonging to different pharmaceutical classes, like antibiotics, antidepressants, anti-inflammatory. In particular, the removal of carbamazepine (CBZ), diclofenac sodium salt (DCF), ciprofloxacin (CPX) and nal…
Determination of soyasaponins I and βg in raw and cooked legumes by solid phase extraction (SPE) coupled to liquid chromatography (LC)-mass spectrome…
2013
Legumes contain a rich variety of phytochemicals as soyasaponins, triterpenoidal glycosides that possess multiple health-promoting properties, such as lowering of cholesterol. In this work, the quantification of soyasaponins I and βg in 60 raw and cooked legumes by using a solid phase extraction (SPE) coupled to a liquid chromatography (LC)-mass spectrometry (MS) method was carried out. Results showed that lentils are a good source of soyasaponins, with a content of soyasaponin I that ranged from 636 to 735 mg kg(-1) and of soyasaponin βg from 672 to 1807 mg kg(-1). The cooking process produced a small loss of soyasaponins in water, that is, 4.8-8.7%, and partially converted soyasaponin βg …