Search results for "Partiti"
showing 10 items of 446 documents
Retention of Carvacrol and Ethyl Acetate in Aqueous Gels of Potato Starch and Konjac Glucomannan
2014
The partition coefficients of two volatile compounds in dispersions containing potato starch (PS) and/or konjac glucomannan (KGM) have been determined by the phase ratio variation method using equilibrium headspace analysis by gas chromatography. The influence of the moment when volatile compounds were added and the effect of the polysaccharide dispersions were investigated. For ethyl acetate, retention by KGM was based on viscosity effect. Retention of carvacrol was important when amylose was accessible. The addition of KGM to PS suspensions decreased the retention governed by interactions with starch.
SPME of 52 pesticides and polychlorinated biphenyls: Extraction efficiencies of the SPME coatings poly(dimethylsiloxane), polyacrylate, poly(dimethyl…
2001
Fiber/water partition coefficients (Kfw) of 52 pesticides, including triazines, organophosphorus pesticides, organochlorine pesticides, and polychlorinated biphenyls (PCBs) were experimentally calculated for the five polymeric coatings poly(dimethylsiloxane) (PDMS), polyacrylate (PA), poly(dimethylsiloxane)-Divinylbenzene (PDMS-DVB), Carboxen-poly(dimethylsiloxane) (CAR-PDMS), and Carbowax-divinylbenzene (CW-DVB) commercially available for solid-phase microextraction coupled to gas chromatography. The equilibrium-time profiles for the five coatings were previously studied in order to establish the time needed for equilibrium. To calculate Kfw the amount of analyte extracted at equilibrium w…
Determination of Diffusion Parameters by a Computer Code (FDP) Based on Mathematica 6.0
2010
A computer code named Fitting for Diffusion Parameters (FDP) based on Mathematica 6.0 has been developed for modeling through- and out-diffusion experiments. FDP was used to determine the diffusion coefficients (De ) and the rock capacity factors (α) for tritiated water (HTO) and 22 Na+ and the distribution coefficient (Kd ) of 22 Na+ in Opalinus Clay (OPA). The values for De and α were obtained by fitting the results of experimental data of both transient and steady-state phases to the analytical solution of accumulated activity. The quality of the parameters De and α was tested by using them as input parameters in the equation of flux. Moreover, the diffusion parameters of HTO and 22 Na+ …
Multiple Protein Sequence Alignment with MSAProbs
2013
Multiple sequence alignment (MSA) generally constitutes the foundation of many bioinformatics studies involving functional, structural, and evolutionary relationship analysis between sequences. As a result of the exponential computational complexity of the exact approach to producing optimal multiple alignments, the majority of state-of-the-art MSA algorithms are designed based on the progressive alignment heuristic. In this chapter, we outline MSAProbs, a parallelized MSA algorithm for protein sequences based on progressive alignment. To achieve high alignment accuracy, this algorithm employs a hybrid combination of a pair hidden Markov model and a partition function to calculate posterior…
General Introduction to Computer Simulation Methods
1986
Computer simulation methods are now an established tool in many branches of science. The motivation for computer simulations of physical systems are manifold. One of the main motivations is that one eliminates approximations with computer simulations. Usually to treat a problem analytically (if it can be done at all) one needs to resort to some kind of approximation; for exam- ple a mean-field-type approximation. With a computer simulation we have the ability to study systems not yet tractable with analytical methods. The computer simulation approach allows one to study complex systems and gain insight into their behaviour. Indeed, the complexity can go far beyond the reach of present analy…
Estimation of the effect of the acidosis and alkalosis on the anesthetic potency of local anesthetics by biopartitioning micellar chromatography and …
2004
Local anesthetics are hydrophobic compounds and weak bases with protonation constants ranged between 7.5 and 8.8. These drugs block reversibly nerve conduction near their site of application or injection and thus produce temporary loss of feeling or sensation in a limited area of the body. The efficacy of anesthetic blockade of local anesthetics depends on the charged/uncharged form ratio and the hydrophobicity of the compounds. In addition their toxicological effects have been reported to be highly dependent on the physiological pH. Biopartitioning micellar chromatography (BMC) and micellar electrokinetic chromatography (MEKC), that use micellar solutions as mobile phases, have proven to b…
Interactions of benzodiazepines with human serum albumin. Circular dichroism studies.
1973
The circular dichroism spectra of 12 benzodiazepine derivatives studied in presence of human serum albumin are presented. Nearly all substances give biphasic extrinsic Cotton effects. At the CD maxima the molar ellipticities and the anisotropy factors are calculated. The influence of the chemical structure of the benzodiazepines on the induced Cotton effect is discussed. There is a linear correlation between the anisotropy factors and the logarithms of the partition coefficients of the substances. It is suggested that the phenyl ring of the benzodiazepine molecule is one of the essential groups for the binding of these substances to human serum albumin.
Quantitative structure-retention relationships for ionic and non-ionic compounds in biopartitioning micellar chromatography
2004
Quantitative structure–retention relationships, QSRRs, represent a powerful tool in chromatography. The objectives of QSRR studies are to predict the chromatographic retention behaviour of solutes based on their structural properties, to elucidate retention mechanisms, to optimize the separation of complex mixtures or to prepare experimental designs. In this paper, using the retention factors of 151 structurally unrelated solutes that cover a wide range of hydrophobicity, molecular size, hydrogen bonding properties and ionization degrees obtained in biopartitioning micellar chromatography (BMC) at different Brij35 micellar concentrations, several multivariate QSRR models are tested. It is d…
A density functional study of flavonoid compounds with anti-HIV activity.
2005
Abstract Quantum chemical calculations at the DFT/B3LYP theory level, with the 6-31G* basis set, was employed to calculate a set of molecular properties of 26 flavonoid compounds with anti-HIV activity. The correlation between biological activity and structural properties was obtained by using the multiple linear regression method. The model obtained showed not only statistical significance but also predictive ability. We demonstrate in this paper that the anti-HIV activity of compounds can be related with the molecular hydrophobicity (ClogP), the electronegativity ( χ ) and the charges on some key atoms, while that the toxicity can be related with the electronic affinities (EA), ClogP and …
Die Aufnahme von Promazin, Chlorpromazin und deren Desmethylmetaboliten in das isoliert perfundierte Rattenhirn
1971
The uptake of promazine, chlorpromazine, desmethylpromazine, and desmethylchlorpromazine into the isolated rat brain was determined in relation to their lipophilic character and their binding to albumin and erythroeytes in the perfusion media. The desmethylmetabolites showed about the same degree of binding as their parent compounds promazine and chlorpromazine. On the other hand the partition coefficients of promazine and chlorpromazine were about 10 times higher than those of their desmethylmetabolites. The more hydrophilic desmethyl-metabolites permeated more slowly into the rat brain, but in the distribution equilibrium they may obviously come up to the same concentration in the brain a…