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Determination of availability of ligand binding site at steady state for topological assessment of receptors with the aid of microcomputers
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The results of testing revealed that the students after the coarse of Clinical pharmacology have a better knewledge on drugs (especially the ones used in general practice) and drug therapy. They are also more critical in the drug assessment of drug effects. In addition to the objective assessment, we are presenting our teaching experience, too.
etermination of ava~la~ili~of ligan assessment of re Chou T.-C. and Chou *, J. Laboratory of Biochemical Pharmacology. Memorial Sloan-Kettering Cancer Center, Cornell University Graduate School l qf Medical Sciences, New York, N. Y. 10021 and * Department of Biochemistry and Molecular Biology, Harvard University, Cambridge M.A. 02138 U.S.A.
By using enzyme kinetic models and the median-effect principle (MEP) of the mass-action law (Chou. 1976) and by combining i) availability of ligand binding site (Chou, 1977); ii) exclusivity of ligand binding (Chou and Talalay, 1977;1981) and iii) competitiveness of ligand binding (Lineweaver-Burk plot). New procedure for topological assessment of receptors can now be made with the aid of a microcomputer software using IBM PC (Chou and Chou, US Copyright, 1989). Fractional availability of ligand binding site at steady state can be determined by Ki/l,, = EJE,, where Ki is the receptor-inhibitor dissociation constant, I,, is the concentration of the inhibitor for 50% inhibition, E, is the amount of receptor available for inhibitor binding and E, is the total amount of receptor. (Chou. 1974) as illustrated by Chou 1977. The exclusivity (mutually exclusive or mutually nonexclusive) of ligand binding, whether in the first order (hyperbolic) or higher order (sigmoidal) can be determined hy the median-effect plot (Chou. 1976; Chou and Talalay, 1984) of MEP with a plot of x = log (inhibitor concentration) vs Y = (fractional inhibition/fraction uninhibited). When the slope of the plot for constituents inhibitors are parallel with the serially diluted mixtime of the inhibitors, the topological relationship is termed mutually exclusive, if the mixture is a concave upward pattern it is termed mutually nonexclusive. The competitiveness (Competitive, noncompetitive and uncompetitive) can be determined by the classical Michaelis-Menten equation with Lineweaver-Burk plot or other plots. Computer software (Chou and Chou, see above) can be used to aid all of the above determinations and graphics. For one agonist and two antagonists, a total of eight possible different topological binding patterns can be differentiated (Chou and Chou, 1988). Conclusion: By combining the above procedures, new methodology for the topological assessments on receptor ligand interaction can now be made which can then be correlated with more detailed physical chemical findings.
References Chou, T.-C. Mol. Pharmacol. 10: 235-247, 1974. Chou, T.-C. J. Theor. Biol. 39: 253-276, 1976. Chou, T.-C. J. Theor. Biol. 65: 245-256, 1977. Chou, T.-C. and Talalay, P.J. Biol. Chem. 252: 6438-6442, 1977. Chou, T.-C. and Talalay, P. Eur. J. B&hem. 115: 207-216, 1981. Chou, T.-C. and Talalay, P. Adv. Enz. Regal 22: 29-55, 1984. Chou, T.-C. and Chou J. FASEB J.2:A1778.1988. Chou, J. and Chou. T.-C. “Dose-Effect Analysis with Microcomputers,” Elsevier-Biosoft. Cambridge, UK. 1989.
The results of testing revealed that the students after the coarse of Clinical pharmacology have a better knewledge on drugs (especially the ones used in general practice) and drug therapy. They are also more critical in the drug assessment of drug effects. In addition to the objective assessment, we are presenting our teaching experience, too.
etermination of ava~la~ili~of ligan assessment of re Chou T.-C. and Chou *, J. Laboratory of Biochemical Pharmacology. Memorial Sloan-Kettering Cancer Center, Cornell University Graduate School l qf Medical Sciences, New York, N. Y. 10021 and * Department of Biochemistry and Molecular Biology, Harvard University, Cambridge M.A. 02138 U.S.A.
By using enzyme kinetic models and the median-effect principle (MEP) of the mass-action law (Chou. 1976) and by combining i) availability of ligand binding site (Chou, 1977); ii) exclusivity of ligand binding (Chou and Talalay, 1977;1981) and iii) competitiveness of ligand binding (Lineweaver-Burk plot). New procedure for topological assessment of receptors can now be made with the aid of a microcomputer software using IBM PC (Chou and Chou, US Copyright, 1989). Fractional availability of ligand binding site at steady state can be determined by Ki/l,, = EJE,, where Ki is the receptor-inhibitor dissociation constant, I,, is the concentration of the inhibitor for 50% inhibition, E, is the amount of receptor available for inhibitor binding and E, is the total amount of receptor. (Chou. 1974) as illustrated by Chou 1977. The exclusivity (mutually exclusive or mutually nonexclusive) of ligand binding, whether in the first order (hyperbolic) or higher order (sigmoidal) can be determined hy the median-effect plot (Chou. 1976; Chou and Talalay, 1984) of MEP with a plot of x = log (inhibitor concentration) vs Y = (fractional inhibition/fraction uninhibited). When the slope of the plot for constituents inhibitors are parallel with the serially diluted mixtime of the inhibitors, the topological relationship is termed mutually exclusive, if the mixture is a concave upward pattern it is termed mutually nonexclusive. The competitiveness (Competitive, noncompetitive and uncompetitive) can be determined by the classical Michaelis-Menten equation with Lineweaver-Burk plot or other plots. Computer software (Chou and Chou, see above) can be used to aid all of the above determinations and graphics. For one agonist and two antagonists, a total of eight possible different topological binding patterns can be differentiated (Chou and Chou, 1988). Conclusion: By combining the above procedures, new methodology for the topological assessments on receptor ligand interaction can now be made which can then be correlated with more detailed physical chemical findings.
References Chou, T.-C. Mol. Pharmacol. 10: 235-247, 1974. Chou, T.-C. J. Theor. Biol. 39: 253-276, 1976. Chou, T.-C. J. Theor. Biol. 65: 245-256, 1977. Chou, T.-C. and Talalay, P.J. Biol. Chem. 252: 6438-6442, 1977. Chou, T.-C. and Talalay, P. Eur. J. B&hem. 115: 207-216, 1981. Chou, T.-C. and Talalay, P. Adv. Enz. Regal 22: 29-55, 1984. Chou, T.-C. and Chou J. FASEB J.2:A1778.1988. Chou, J. and Chou. T.-C. “Dose-Effect Analysis with Microcomputers,” Elsevier-Biosoft. Cambridge, UK. 1989.