Dissociative half-life

Enzyme Inhibitor Apparent k (M-V1) Apparent koS (s-1) Dissociation Half-life... 

The idea of drug-target residence time places less emphasis on the strength of receptor-ligand interaction and more emphasis on the duration of receptor-ligand interaction. The duration of interaction is defined as the residence time (t) of the ligand, which is equal to the inverse of koff (Equation 5.23). A closely related variable is dissociative half-life (/, 2), also defined by koll (Equation 5.24).31... 

Gadolinium-containing chelate Structure Charge Thermodynamic stability Kinetic stability (Dissociation half-life at pH 1.0) Amount of excess chelate (mg/ml)... 

However when high micromolar concentrations (200 micro M) of 5-HT or of 5-HT uptake inhibitors were used in determining the dissociation half life of H-imipramine, H-paroxetine and H-dtalopram dissociating from human platelet membrane preparations it appears that not only the dissociation half life was prolonged but also that the prolongation was different for each of the three labeled uptake inhibitors [24]. This led to the conclusion that the three labeled ligands each bind to a different domain on the 5-HT transporter. 

Furthermore the authors showed that the dissociation kinetics of H-citalopram in membrane preparations of human platelets and human brain (putamen) both appeared to be affected differently by different 5-HT uptake inhibitors at 200 micromolar concentration. For instance 5-HT, clovoxamine and fluvoxamine had no effect on the dissociation half life while indalpine shortened and other 5-HT uptake inhibitors prolonged the dissociation half life of H-citalopram in both transporter preparations [24],... 

One of the successful radical homopolymerizations of VPA was performed by Levin et al in DMF in the presence of AIBN as initiator, in a yield of 95%. PVPA was obtained in protic solvents both from pure VPA, crude VPA , and ester-containing crude VPA in the presence of initiator. Suitable protic solvents were water and aliphatic alcohols such as isopropanol, which keep the mixtures stirrable and workable. The free radical initiators that can be used are peroxides such as dibenzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl pero3gr-2-ethylhexanoate, and ammonium or potassium persulfate. The amount of initiator necessary is 1.5-4% versus monomer and depends directly on the amount of diluent. The authors recommend that the calculated amount of initiator be added in equal portions during the reaction, after the reaction temperature has been reached, because the polymerization is highly exothermic at the start when the monomer concentration is high and relatively higher residual monomer content could be obtained. The reaction temperature was maintained between 80 °C and 110 °C and depends on the dissociation half-life of the initiator. A reaction time of between 5 and 12 h is approximately inversely proportional to the concentration of VPA monomer in solvent. The yield of PVPA varied from 32% to 60% when peroxide initiators were used and from 3% to 6% when ammonium or potassium persulfate were used. Pure PVPA can be obtained by precipitation. The homopolymerization of VPA in methanol did not occur. ... 

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