Search results for "Kinetics"

Studies of polyamines transport through liquid membranes with D2EHPA as a carrier.

2008

The transport of polyamines through the liquid membranes with di‐2‐ethylhexyl phosphoric acid (D2EHPA) was investigated. The study was performed in three main steps: liquid–liquid extraction (LLE), bulk liquid membrane (BLM) extraction, and supported liquid membrane (SLM) extraction. Equilibrium distribution experiments allowed determining the extraction constants and stoichiometric coefficients for each polyamine. It turned out that one amino group binds two molecules of carrier (one D2EHPA dimer) and the extractability of polyamine rises with the increase in number of function groups in the molecule. The BLM and SLM experiments showed that despite considerable differences in distribution …

Directed Assembly of Soft Colloids through Rapid Solvent Exchange

2015

We studied the directed assembly of soft nanoparticles through rapid micromixing of polymers in solution with a nonsolvent. Both experiments and computer simulations were performed to elucidate the underlying physics and to investigate the role of various process parameters. In particular, we discovered that no external stabilizing agents or charged end groups are required to keep the colloids separated from each other when water is used as the nonsolvent. Furthermore, the size of the nanoparticles can be reliably tuned through the mixing rate and the ratio between polymer solution and nonsolvent. Our results demonstrate that this mechanism is highly promising for the mass fabrication of un…

Delta 5-desaturation of dihomogammalinolenic acid (20:3(n-6)) into arachidonic acid (20:4(n-6)) by rat liver microsomes and incorporation of fatty ac…

1991

Abstract Liver microsomes of rats fed an essential fatty acid (EFA)-deficient diet or a commercial balanced diet were used to study the effect of incubation time on the Δ 5 -desaturation of [ 14 C] dihomogammalinolenic acid (20:3( n −6)) into arachidonic acid (20:4( n −6)) and incorporation of the two acids into microsomal phospholipids. The EFA-deficient diet highly increased the desaturation rate of 20:3( n −6). Incorporation of the formed 20:4( n −6) into microsomal phospholipids was also increased but at saturating concentration of substrate only. At early times of incubation, the precursor 20:3( n −6) was rapidly incorporated into phospholipids. Formation and incorporation of 20:4( n −…

Psychosocial stress, catecholamines, and essential fatty acid metabolism in rats.

1994

To examine the effects of psychosocial stress and the "stress hormone," epinephrine, on essential fatty acid metabolism in rats, two studies were conducted. In the first, the effects of four weeks of (i) social isolation and (ii) group housing (control) on liver microsomal delta 6 and delta 5 n-6 desaturase activity were studied in group-reared male normotensive (Wistar Kyoto) and spontaneously hypertensive (SHR) rats (n = 5/group). The second study examined the effects of acute ip epinephrine (0.0, 1.0, 2.0, and 4.0 mg/kg) 6 hr prior to and following an ig dose (4 g/kg) of safflower oil (rich in 18:2n-6, LA) on plasma and liver LA, 20:4n-6 (AA), and LA/AA ratios in adult essential fatty ac…

FeCr2O4 synthetic spinel: heating experiments and oxidation kinetics

2011

Cover Feature: Excited‐State Kinetics of an Air‐Stable Cyclometalated Iron(II) Complex (Chem. Eur. J. 51/2019)

2019

Differences in tissue distribution of iron from various clinically used intravenous iron complexes in fetal avian heart and liver.

2015

Abstract Nanomedicines are more complex than most pharmacologically active substances or medicines and have been considered as non-biological complex drugs. For nanomedicines pivotal pharmacokinetic properties cannot be assessed by plasma concentration data from standard bioequivalence studies. Using intravenous iron complexes (IICs) as model we show that fetal avian tissues can be used to study time dependent tissue concentrations in heart and liver. Clear differences were found between equimolar doses of sucrose, gluconate or carboxymaltose coated iron particles. The range in tissue iron concentrations observed with these clinically widely used IICs provides an orientation as to what shou…

Heavy enzymes—experimental and computational insights in enzyme dynamics

2014

The role of protein motions in the chemical step of enzyme-catalyzed reactions is the subject of an open debate in the scientific literature. The systematic use of isotopically substituted enzymes has been revealed as a useful tool to quantify the role of these motions. According to the Born-Oppenheimer approximation, changing the mass of the protein does not change the forces acting on the system but alters the frequencies of the protein motions, which in turn can affect the rate constant. Experimental and theoretical studies carried out in this field are presented in this article and discussed in the framework of Transition State Theory.

Bidirectional membrane transport: Simulations of transport inhibition in uptake studies explain data obtained with flavonoids

2006

The purpose of the simulations was to obtain an estimate of concentration-dependent uptake curves when two counteracting transporters are present. On the basis of this experimental data obtained with a pair of ovarian carcinoma cell lines, one of which was not expressing the exsorptive transporter P-glycoprotein and one of which was an MDR1-transfected, P-glycoprotein expressing variant, the kinetics of cellular uptake of the radiolabel (3)H-talinolol were calculated and the inhibitory constants at P-gp were determined for different flavonoids. With respect to the inhibition of P-gp function, among others, naringenin and isoquercitrin were identified as inhibitors, yet estimation of the inh…

Urea as a PCDD/F inhibitor in municipal waste incineration.

2001

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from municipal waste incineration have been widely studied because of their extensive toxicity, and many efforts have been made to restrict their emissions. Although a number of chemical compounds have been shown in laboratory-scale tests to inhibit the formation of PCDD/Fs, few have been tested in pilot- or full-scale plants. This work evaluates the effect of urea as a PCDD/F inhibitor in a pilot-scale incinerator that uses refuse-derived fuel (RDF). The decomposition of urea under the test conditions was also studied using detailed kinetic modeling. An aqueous solution of urea was injected into the flue gas stream …