scholarly journals Effect of liposomal phospholipid composition on cholesterol transfer between microsomal and liposomal vesicles

1986 ◽  
Vol 238 (3) ◽  
pp. 647-652 ◽  
Author(s):  
C Bhuvaneswaran ◽  
K A Mitropoulos
Keyword(s):  
Activation Energy ◽  
Enzyme Activity ◽  
Control System ◽  
Phospholipid Composition ◽  
Acyltransferase Activity ◽  
Phosphatidylcholine Liposomes ◽  
First Order ◽  
First Order Kinetics ◽  
Phospholipid Liposomes

Preincubation of rat liver microsomal vesicles at 37 degrees C in the presence of [3H]cholesterol/phospholipid liposomes results in a net transfer of cholesterol from liposomes to microsomal vesicles. This transfer follows first-order kinetics. For similar concentrations of the donor vesicles, rates of transfer are about 6-8 times lower with cholesterol/sphingomyelin liposomes compared with cholesterol/phosphatidylcholine liposomes. Also, transfer of cholesterol from cholesterol/sphingomyelin liposomes to microsomal vesicles reveals a larger activation energy than for the process from cholesterol/phosphatidylcholine liposomes. There is a significant correlation between the amount of liposomal cholesterol transferred to microsomal vesicles during preincubation and the increase found with acyl-CoA:cholesterol acyltransferase activity in these microsomes over their corresponding controls. If, however, liposomes made solely of phospholipids are substituted for the cholesterol/phospholipid liposomes in the preincubation system containing microsomal vesicles, then the acyl-CoA:cholesterol acyltransferase activity is decreased compared with the corresponding control system. Both sphingomyelin and phosphatidylcholine liposomes are equally effective in decreasing the enzyme activity. These results offer direct kinetic evidence for the positive correlation between cholesterol and sphingomyelin found in vivo in biological membranes.

scholarly journals Comparative Study of Chemical Stability of Two H1Antihistaminic Drugs, Terfenadine and ItsIn VivoMetabolite Fexofenadine, Using LC-UV Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Rafał Pietraś ◽  
Izabela Kozak ◽  
Karolina Lejwoda ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chemical Stability ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Degradation ◽  
Effects Of Temperature ◽  
High Doses ◽  
Antihistaminic Drugs ◽  
Kinetics Of

A comparative study of chemical stability of terfenadine (TER) and itsin vivometabolite fexofenadine (FEX) was performed. Both TER and FEX were subjected to high temperature at different pH and UV/VIS light at different pH and then quantitatively analyzed using new validated LC-UV methods. These methods were used to monitor the degradation processes and to determine the kinetics of degradation for both the compounds. As far as the effects of temperature and pH were concerned, FEX occurred more sensitive to degradation than TER. As far as the effects of UV/VIS light and pH were concerned, the both drugs were similarly sensitive to high doses of light. Using all stress conditions, the processes of degradation of TER and FEX followed the first-order kinetics. The results obtained for these two antihistaminic drugs could be helpful in developing their new derivatives with higher activity and stability at the same time.

scholarly journals Optimization, Kinetics, Thermodynamic and Arrhenius Model of the Removal of Ciprofloxacin by Internal Electrolysis with Fe-Cu and Fe-C Materials

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2110
Author(s):  
Tra Huong Do ◽  
Xuan Linh Ha ◽  
Thi Tu Anh Duong ◽  
Phuong Chi Nguyen ◽  
Ngoc Bich Hoang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Ph Value ◽  
Arrhenius Model ◽  
First Order ◽  
Chemical Plating ◽  
First Order Kinetics ◽  
Internal Electrolysis ◽  
Plating Method ◽  
Rapid Removal ◽  
Pseudo First Order

The ciprofloxacin (CIP) removal ability of a Fe-Cu electrolytic material was examined with respect to pH (2–9), time (15–150 min), shaking speed (100–250 rpm), material mass (0.2–3 g/L), temperature (298, 308, 323) and initial CIP concentration (30–200 mg/L). The Fe-Cu electrolytic materials were fabricated by the chemical plating method, and Fe-C materials were mechanically mixed from iron powder and graphite. The results show that at a pH value of 3, shaking time 120 min, shaking speed 250 rpm, a mass of Fe-Cu, Fe-C material of 2 g/L and initial CIP concentration of 203.79 mg/L, the CIP removal efficiency of Fe-Cu material reached 90.25% and that of Fe-C material was 85.12%. The removal of CIP on Fe-Cu and Fe-C materials follows pseudo-first-order kinetics. The activation energy of CIP removal of Fe-Cu material is 14.93 KJ/mol and of Fe-C material is 16.87 KJ/mol. The positive ΔH proves that CIP removal is endothermic. A negative entropy of 0.239 kJ/mol and 0.235 kJ/mol (which is near zero and is also relatively positive) indicated the rapid removal of the CIP molecules into the removed products.

Reaction Kinetics of Thrombin Activity in Decalcified Plasma and Blood

1969 ◽  
Vol 21 (03) ◽  
pp. 580-593
Author(s):  
L. A Pálos ◽  
G Sas ◽  
A Csurgay
Keyword(s):  
Reaction Kinetics ◽  
Mathematical Expression ◽  
Second Phase ◽  
Thrombin Time ◽  
First Order ◽  
Functional Relationships ◽  
First Order Kinetics ◽  
Set Up ◽  
Kinetics Of

SummaryThe reaction kinetics of the second phase of blood clotting (conversion of fibrinogen to fibrin) has been studied in euglobulin and thrombin-antithrombin systems. It was intended to set up relationships that would make mathematical expression of the processes possible and which would, moreover, help in detecting dynamic and functional relationships characteristic of the mechanism involved in coagulation.The experiments have yielded the following results:1. In the euglobulin solution containing no antithrombin the fibrinogen-thrombin reaction can be characterized with a constant deviation from the first order kinetics.2. The process of thrombin inactivation is a reaction of first order in the initial phase.3. The two basic processes (clotting by thrombin in euglobulin solution, inactivation of thrombin in defibrinated plasma) make it possible to predetermine the thrombin time of citrated plasma. Theoretical and actual clotting times were in good agreement.4. The thrombin time of plasma can be computed even if thrombin is not introduced to the system at one stride but gradually, a manner of administration which is a better imitation of what happening in vivo. 5. In connection with the computation of the “thrombin time” of citrated blood, we determined experimentally (and expressed by means of a function) the modification produced by the corpuscular elements of the blood in the reaction between fibrinogen and thrombin under atraumatic conditions.

scholarly journals Hepatic uptake and metabolism of galactose can be quantified in vivo by 2-[18F]fluoro-2-deoxygalactose positron emission tomography

2008 ◽  
Vol 295 (1) ◽  
pp. G27-G36 ◽  
Author(s):  
Michael Sørensen ◽  
Ole Lajord Munk ◽  
Frank Viborg Mortensen ◽  
Aage Kristian Olsen ◽  
Dirk Bender ◽  
...  
Keyword(s):  
Removal Rate ◽  
Hepatic Uptake ◽  
Metabolic Clearance ◽  
Blood Concentrations ◽  
First Order ◽  
First Order Kinetics ◽  
Significant Difference ◽  
Saturation Kinetics ◽  
Uptake And Metabolism

Metabolism of galactose is a specialized liver function. The purpose of this PET study was to use the galactose analog 2-[18F]fluoro-2-deoxygalactose (FDGal) to investigate hepatic uptake and metabolism of galactose in vivo. FDGal kinetics was studied in 10 anesthetized pigs at blood concentrations of nonradioactive galactose yielding approximately first-order kinetics (tracer only; n = 4), intermediate kinetics (0.5–0.6 mmol galactose/l blood; n = 2), and near-saturation kinetics (>3 mmol galactose/l blood; n = 4). All animals underwent liver C15O PET (blood volume) and FDGal PET (galactose kinetics) with arterial and portal venous blood sampling. Flow rates in the hepatic artery and the portal vein were measured by ultrasound transit-time flowmeters. The hepatic uptake and net metabolic clearance of FDGal were quantified by nonlinear and linear regression analyses. The initial extraction fraction of FDGal from blood-to-hepatocyte was unity in all pigs. Hepatic net metabolic clearance of FDGal, KFDGal, was 332–481 ml blood·min−1·l−1 tissue in experiments with approximately first-order kinetics and 15.2–21.8 ml blood·min−1·l−1 tissue in experiments with near-saturation kinetics. Maximal hepatic removal rates of galactose were on average 600 μmol·min−1·l−1 tissue (range 412–702), which was in agreement with other studies. There was no significant difference between KFDGal calculated with use of the dual tracer input (KdualFDGal) or the single arterial input (KarterialFDGal). In conclusion, hepatic galactose kinetics can be quantified with the galactose analog FDGal. At near-saturated kinetics, the maximal hepatic removal rate of galactose can be calculated from the net metabolic clearance of FDGal and the blood concentration of galactose.

Reactions with half-lives of several years

1964 ◽  
Vol 17 (4) ◽  
pp. 406 ◽  
Author(s):  
GA Bottomley ◽  
GL Nyberg
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Virial Coefficient ◽  
Energy Equation ◽  
Second Virial Coefficient ◽  
First Order ◽  
First Order Kinetics ◽  
Reciprocal Temperature ◽  
Temperature Activation

The gas-phase thermal decomposition of dimethyldiazirine, (CH3)2CN2, at very slow rates has been investigated using precision gas-volumetric techniques previously applied to second virial coefficient studies. At 50-70� the first-order kinetics correspond to half-lives about 0.3-3.0 years. The present results, together with data obtained by other workers using conventional apparatus at 124-174�, fit a single log rate-reciprocal temperature activation energy equation.

Synaptosomal Na+,K+-ATPase as a membrane probe in studying the in vivo action of morphine

1981 ◽  
Vol 59 (8) ◽  
pp. 687-692 ◽  
Author(s):  
Ophelia Wan-Kan ◽  
E. A. Hosein
Keyword(s):  
Activation Energy ◽  
Enzyme Activity ◽  
Transition Temperature ◽  
Specific Activity ◽  
Membrane Phospholipids ◽  
Membrane Probe ◽  
Biphasic Effect ◽  
Brain Synaptosomes ◽  
Membrane Bound

The activity of membrane-bound Na+,K+-ATPase was used as a metabolic probe to study the effects of morphine in vivo in rat brain synaptosomes. Arrhenius plots were generated to study an induced perturbation within the membrane. In acute studies 0.5-h postmorphine, the drug was without effect on the basal activity of the enzyme. With dopamine-stimulated Na+,K+-ATPase morphine decreased the apparent transition temperature and specific activity of the enzyme while there was a slight stimulation in its activation energy. An increase in these parameters was observed in samples taken from animals withdrawn from the drug for 48 h. These results strongly suggest the possible involvement of the membrane phospholipids as transducer which mediates the observed biphasic effect of the drug on enzyme activity.

scholarly journals The dissociation energy of the C-N bond in benzylamine

1949 ◽  
Vol 198 (1053) ◽  
pp. 285-292 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Dissociation Energy ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Kcal Mole ◽  
First Order ◽  
First Order Kinetics ◽  
Permanent Gases ◽  
Kinetics Of

The kinetics of the thermal decomposition of benzylamine were studied by a flow method using toluene as a carrier gas. The decomposition produced NH 3 and dibenzyl in a molar ratio of 1:1, and small quantities of permanent gases consisting mainly of H 2 . Over a temperature range of 150° (650 to 800° C) the process was found to be a homogeneous gas reaction, following first-order kinetics, the rate constant being expressed by k = 6 x 10 12 exp (59,000/ RT ) sec. -1 . It was concluded, therefore, that the mechanism of the decomposition could be represented by the following equations: C 6 H 5 . CH 2 . NH 2 → C 6 H 5 . CH 2 • + NH 2 •, C 6 H 5 . CH 3 + NH 2 •→ C 6 H 5 . CH 2 • + NH 3 , 2C 6 H 5 . CH 2 •→ dibenzyl, and the experimentally determined activation energy of 59 ± 4 kcal./mole is equal to the dissociation energy of the C-N bond in benzylamine. Using the available thermochemical data we calculated on this basis the heat of formation of the NH 2 radical as 35.5 kcal./mole, in a fair agreement with the result obtained by the study of the pyrolysis of hydrazine. A review of the reactions of the NH 2 radicals is given.

scholarly journals Temperature and pH effects on the kinetics of 2-aminophenol auto-oxidation in aqueous solution

2003 ◽  
Vol 1 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Dumitru Oancea ◽  
Mihaela Puiu
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Aqueous Solution ◽  
Ph Effects ◽  
Influence Of Temperature ◽  
First Order ◽  
Incremental Methods ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetics Of

AbstractThe kinetics of the auto-oxidation of 2-aminophenol (OAP) to 2-amino-phenoxazin-3-one (APX) was followed in air-saturated aqueous solutions and the influence of temperature and pH on the auto-oxidation rate was studied. The kinetic analysis was based on a spectrophotometric method following the increase of the absorbance of APX. The process follows first order kinetics according to the rate law—d[OAP]/dt=k′[OAP]. The experimental data, within the pH range 4–9.85, were analyzed using both differential and incremental methods. The temperature variation of the overall rate constant was studied at pH=9.85 within the range 25–50°C and the corresponding activation energy was evaluated.

AN INDEPENDENT METHOD FOR OBTAINING THE ACTIVATION ENERGY OF THERMOLUMINESCENCE GLOW PEAKS

2004 ◽  
Vol 18 (20n21) ◽  
pp. 2877-2885 ◽  
Author(s):  
M. S. RASHEEDY
Keyword(s):  
Activation Energy ◽  
Glow Peak ◽  
Independent Method ◽  
Heating Rates ◽  
First Order ◽  
First Order Kinetics ◽  
General Order ◽  
Luminescence Process ◽  
The Common ◽  
Kinetics Order

The activation energy E (eV) of the first-order thermoluminescence (TL) glow peak is currently obtained using a two heating rates method. However, this method having the common drawback, that it assumes the first-order kinetics in the luminescence process. In the present work, an equation is suggested to determine the activation energy E (eV) of any glow peak, independent on the kinetics order of the process. To apply this method, three heating rates (β1,β2,β3), the corresponding peak temperatures (T1,T2,T3) and intensities (I1,I2,I3) of the isolated glow peaks are required. The applicability of the suggested method is demonstrated here by taking some numerically computed first-, second- and general-order TL glow peaks.

The effect of temperature on the aggregation kinetics of partially bare gold nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (85) ◽  
pp. 82138-82149 ◽  
Author(s):  
Anushree Dutta ◽  
Anumita Paul ◽  
Arun Chattopadhyay
Keyword(s):  
Activation Energy ◽  
Gold Nanoparticles ◽  
Effect Of Temperature ◽  
Aggregation Kinetics ◽  
Temperature Dependent ◽  
Colloidal Aggregation ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of ◽  
Bare Gold

Temperature dependent aggregation reaction of partially bare gold nanoparticles showed a first order kinetics and prevalence of reaction limited colloidal aggregation with an activation energy equal to 36.2 ± 3.0 kJ mol−1.

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