Search results for "Solubility"
showing 10 items of 681 documents
Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives
2012
2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent acidic hydrolysis. The electrolysis is conducted in propylene carbonate circumventing toxic and expensive acetonitrile. The protocol is simple to perform and superior to other chemical or electrochemical methods. The key of the method is based on the low solubility of the anodically trimerized product. The shift of potentials is supported by cyclic voltammetry studies.
Optimization of the Ussing chamber setup with excised rat intestinal segments for dissolution/permeation experiments of poorly soluble drugs.
2016
AbstractContext: Prediction of the in vivo absorption of poorly soluble drugs may require simultaneous dissolution/permeation experiments. In vivo predictive media have been modified for permeation experiments with Caco-2 cells, but not for excised rat intestinal segments.Objective: The present study aimed at improving the setup of dissolution/permeation experiments with excised rat intestinal segments by assessing suitable donor and receiver media.Methods: The regional compatibility of rat intestine in Ussing chambers with modified Fasted and Fed State Simulated Intestinal Fluids (Fa/FeSSIFmod) as donor media was evaluated via several parameters that reflect the viability of the excised in…
DNA-replication complex from cells infected with herpes virus.
2005
Herpes simplex virus (HSV) DNA synthesis is initiated in an intact cell system by a 36-residue ribonucleotide stretch [W.E.G. Müller, R.K. Zahn, J. Arendes, and D. Falke (1979) Virology, 98, 200-210]. In the present study a nucleoplasmic fraction was isolated from rabbit kidney cells infected with HSV (type 1), which catalyzes DNA synthesis. By means of specific assays, containing single-stranded deoxyribopolymers, it was elucidated that the replication complex contains both an RNA-synthesizing and a DNA-synthesizing enzyme. These enzymes were characterized as host cell RNA polymerase II and HSV-induced DNA polymerase. The RNA polymerase II synthesizes an RNA initiator with an average chain…
Polyphosphate, the physiological metabolic fuel for corneal cells: a potential biomaterial for ocular surface repair
2019
The regeneration of the epithelium, covering the avascular cornea, involves the processes of differentiation, proliferation and migration of cells originating from the corneal epithelial stem cells. We ask the question if these energy-consuming processes can be fueled by the physiological, inorganic polyphosphate (polyP), the main energy storage/donor molecule in the extracellular space. The ex vivo results reveal that addition of polyP, in the form of soluble Na-polyP, to the culture medium elicits a strong stimulatory effect on cell viability/growth and migration of corneal epithelial cells. Microscopic analyses of partially denuded cornea specimens show that in the presence of polyP, but…
Dissolution enhancement and in vitro performance of clarithromycin nanocrystals produced by precipitation–lyophilization–homogenization method
2014
The gastroduodenal diseases caused by Helicobacter pylori were commonly treated with antibiotic clarithromycin as a standard regimen. According to the poorly water-soluble of clarithromycin, the nanocrystal formulation was prepared. The aim of this study was to investigate an enhancement effect of clarithromycin nanocrystals produced by precipitation-lyophilization-homogenization (PLH) method on the saturation solubility, dissolution velocity, antibiotic activity, permeability through the gastric mucus and cellular permeability. Poloxamer 407 and sodium lauryl sulfate (SLS) were chosen as combined stabilizers in the nanocrystal system. The obtained clarithromycin nanocrystals were identifie…
Physico-chemical parameters determining hydration and particle interactions during the setting of silicate cements
1997
Abstract Hydration of tricalcium silicate (Ca 3 SiO 5 ), the pure phase used as a model of the portland cements, is the chemical process leading to the formation of hydrates, while setting is a definite time event corresponding to the change of the paste from the soft to the hard state. Setting results from interactions between anhydrous or very partially hydrated particles. The analysis of these interactions leads to the identification of two fundamental steps: the coagulation of cement grains during the first minutes following the mixing and the rigidification of the coagulated structure which arises simultaneously with the acceleration of the calcium silicate hydrates (CSH) formation. …
New polyamine drugs as more effective antichagas agents than benznidazole in both the acute and chronic phases.
2018
Abstract Despite the continuous research effort that has been made in recent years to find ways to treat the potentially life threatening Chagas disease (CD), this remains the third most important infectious disease in Latin America. CD is an important public health problem affecting 6–7 million people. Since the need to search for new drugs for the treatment of DC persists, in this article we present a panel of new polyamines based on the tripodal structure of tris(2-aminomethyl)amine (tren) that can be prepared at low cost with high yields. Moreover, these polyamines present the characteristic of being water-soluble and resistant to the acidic pH values of stomach, which would allow their…
The preparation of four- and six-membered chalcogenametallacyclic derivatives of group 4 metallocenes
1989
Abstract Four-membered metallacycles [(RC 5 H 4 ) 2 M(μ-E)] 2 (M = Zr, Hf; 1 , E = Se; 2 , E = S) were obtained by UV irradiation of dialkyl- or diaryl-metallocenes and equimolecular amounts of elemental chalcogen, but this method works only for bulky R groups. A more general route to compounds 1 and 2 involves the reaction of metallocene dichloride with chalcogenide anions. Six-membered metallacyclohexasulfanes (t-BuC 5 H 4 ) 2 MS 5 ( 3 , M = Zr, Hf) are obtained rather than compounds 2 when an excess of sulfur is used in the photolytic experiments, whereas compounds 1 were still formed when an excess of selenium was used. The observed difference is explained in terms of the solubility of …
Albumin binding and hydrophobic character of promazine and chlorpromazine metabolites.
1972
1. The binding of didesmethylpromazine, promazine N-oxide, 2-hydroxypromazine, promazine sulfoxide, monodesmethylpromazine sulfoxide, didesmethylchlorpromazine, chlorpromazine N-oxide, and chlorpromazine sulfoxide to bovine serum albumin was determined by means of sephadex gel filtration. 2. The albumin binding of these substances was characterized by the following parameters: the percentage α of free substance, the percentage β of bound substance, the binding constants K1, k+ and m, the number of binding sites per albumin molecule, and the free binding energy ΔFo. 3. The partition coefficients between n-octanol and buffer solution, pH 7.40, were measured for the above mentioned metabolites…
Isolation of oligopeptides from the water-soluble extract of goat cheese and their identification by mass spectrometry
2001
A procedure for the separation and identification of small peptides from the water-soluble fraction of a goat cheese was developed. The water-soluble extract was ultrafiltered (1000 Da membrane cutoff), and peptides were isolated by sequential chromatography: size exclusion chromatography (HPLC-grade water), anion exchange chromatography (phosphate buffer gradient), and semipreparative reverse-phase high-performance liquid chromatography (water/acetonitrile gradient). The fractions obtained were analyzed by combined mass spectrometry methods including electrospray ionization, liquid secondary ionization, and tandem mass spectrometry to identify and to confirm the sequences of 28 tri- to oct…