Crossed‐Beam Studies of Energy Dependence of Intermediate Complex Formation in an Ion–Molecule Reaction

1969 ◽  
Vol 51 (1) ◽  
pp. 452-454 ◽  
Author(s):  
Z. Herman ◽  
A. Lee ◽  
R. Wolfgang
Keyword(s):  
Complex Formation ◽  
Energy Dependence ◽  
Intermediate Complex ◽  
Molecule Reaction

Dynamics of the ion-molecule reaction D2O+ (NH3, NH2) HD2O+ from crossed-beam scattering experiments

1988 ◽  
Vol 53 (10) ◽  
pp. 2168-2174 ◽  
Author(s):  
Jan Vančura ◽  
Zdeněk Herman
Keyword(s):  
Collision Energy ◽  
Intermediate Complex ◽  
Atom Transfer ◽  
Molecule Reaction ◽  
Scattering Experiment ◽  
Critical Configuration ◽  
Beam Scattering

Dynamics of the HD2O+ formation in the reaction of D2O+ and NH3 was investigated in a crossed-beam scattering experiment. At T = 1·5 eV (c.m.) the product is formed simultaneously by two different collision mechanisms, by a direct H-atom transfer and by the decomposition of an intermediate complex (D2O.NH3)+; the probabilities of the two mechanisms are about equal at this collision energy. The scattering makes it possible to suggest that in the critical configuration the intermediate complex is a prolate, near-linear species D2OH+.NH2.

scholarly journals Cytochrome P-450 complex formation in rat liver by the antibiotic tiamulin.

1996 ◽  
Vol 40 (1) ◽  
pp. 50-54 ◽  
Author(s):  
R F Witkamp ◽  
S M Nijmeijer ◽  
A S van Miert
Keyword(s):  
Complex Formation ◽  
Selective Inhibition ◽  
Farm Animals ◽  
Intermediate Complex ◽  
Metabolic Intermediate ◽  
Dose Dependent ◽  
Cytochrome P 450 ◽  
Related Compounds ◽  
Substrate Concentrations ◽  
Different Doses

Tiamulin is a semisynthetic diterpene antibiotic frequently used in farm animals. The drug has been shown to produce clinically important--often lethal--interactions with other compounds. It has been suggested that this is caused by a selective inhibition of oxidative drug metabolism via the formation of a cytochrome P-450 metabolic intermediate complex. In the present study, rats were treated orally for 6 days with tiamulin at two different doses: 40 and 226 mg/kg of body weight. For comparison, another group received 300 mg of triacetyloleandomycin (TAO) per kg, which is equivalent to the 226-mg/kg tiamulin group. Subsequently, microsomal P-450 contents, P-450 enzyme activities, metabolic intermediate complex spectra, and P-450 apoprotein concentrations were assessed. In addition, effects on individual microsomal P-450 activities were studied in control microsomes at different tiamulin and substrate concentrations. In the rats treated with tiamulin, a dose-dependent complex formation as evidenced by its absorption spectrum and an increase in cytochrome P-4503A1/2 contents as assessed by Western blotting (immunoblotting) were found. The effects were comparable to those of TAO. Tiamulin induced microsomal P-450 content, testosterone 6 beta-hydroxylation rate, erythromycin N-demethylation rate, and the ethoxyresorufin O-deethylation activity. Other activities were not affected or decreased. When tiamulin was added to microsomes of control rats, the testosterone 6 beta-hydroxylation rate and the erythromycin N-demethylation were strongly inhibited. It is concluded that tiamulin is a potent and selective inducer-inhibitor of cytochrome P-450. Though not belonging to the macrolides, the compound produces an effect on P-450 similar to those of TAO and related compounds.

Sign in / Sign up

Export Citation Format

Share Document