Overview of the detection methods for equilibrium dissociation constant KD of drug-receptor interaction

Drug-receptor interaction plays an important role in a series of biological effects, such as cell pro- liferation, immune response, tumor metastasis, and drug delivery. Therefore, the research on drug-re- ceptor interaction is growing rapidly. The equilibrium dissociation constant （KD） is the basic parameter to evaluate the binding property of the drug-receptor. Thus, a variety of analytical methods have been established to determine the KD values, including radioligand binding assay, surface plasmon resonance method, fluorescence energy resonance transfer method, affinity chromatography, and isothermal ti- tration calorimetry. With the invention and innovation of new technology and analysis method, there is a deep exploration and comprehension about drug-receptor interaction. This review discusses the differ- ent methods of determining the KD values, and analyzes the applicability and the characteristic of each analytical method. Conclusively, the aim is to provide the guidance for researchers to utilize the most appropriate analytical tool to determine the KD values.

Determining PPARg-ligand binding affinity using fluorescent assay with cis-parinaric acid as a probe

Upon the study of small-molecules binding to proteins, the traditional methods for calculating dissociation constants (Kd and Ki) have shortcomings in dealing with the single bind- ing site models. In this paper, two equations have been derived to solve this problem. These two equations are independent of the total concentration or initial degree of saturation of receptor and the activity of the competitive molecule. Through nonlinear fitting against these two equations, Kd value of a probe can be obtained by binding assay, and Ki value of a ligand can be obtained by competitive assay. Moreover, only the total concentrations of receptor([R]t), ligand([L]t) and probe([P]t) are required for the data fitting. In this work, Ki values of some typical ligands of PPARγ were successfully determined by use of our equations, among which the Ki value of PPARγ-LY171883 was reported for the first time.

EffectofElectroacupunctureonPulmonaryβ－AdrenoceptorinAllergicAsthmaGuinea－Pigs

Twenty four male guinea-pigs were randomly divided into 3 groups: Group A, allergic asthmaguinea-pigs prepared by peritoneal injection and spraying inhalation of albumin; Group B, allergic asthmaguinea-pigs treated with electroacupuncture through stimulating the acupoint Feishu (UB13 ) and Group C, thecontrol group. With[3H] -DHA as a radioligand, pulmonary adrenoceptor ( AC) in the 3 groups of guinea-pigs were detrermined by radioligand binding assay technique. The results showed that: ( 1 ) The maximumbinding volume of receptor ligand ( Bmax, fmol/mg prot. ) of pulmonary AC in Group A (123. 86 42. 91 )was significantly lower than that in group C (199 . 54 37. 03 , P< 0. 05) , while the difference between groupB ( 142. 00 42. 91 ) and group C was not significant ( P > 0. 05 ) . ( 2 ) The Kd ( nM) of pulmonary AC ingroup A, B and C were 5 . 10 1 . 39 , 6. 53 2 . 41 and 8. 72 2 . 02 respectively, and the differences amongthe three groups were not significant ( P >0. 05) . The results indicated that the decrease of the content anddysfunction of pulmonary AC in allergic asthma guinea-pigs might be regulated by electroacupuncture thera-py.