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Wednesday, October 10, 2012

QSAR History

More than a 120 year ago, Crum-Brown and Fraser expressed the idea that the physiological action of a substance was a function of its chemical composition and constitution.4 A few decades later, in 1893, Richet showed that the cytotoxicities of a diverse set of simple organic molecules were inversely related to their corresponding water solubilities4.
At the turn of the 20th century, Meyer and Overton independently suggested that the narcotic (depressant) action of a group of organic compounds paralleled their olive oil/water partition coefficients. In 1939 Ferguson introduced a thermodynamic generalization to the correlation of depressant action with the relative saturation of volatile compounds in the vehicle in which they were administered. The extensive work of Albert, and Bell and Roblin established the importance of ionization of bases and weak acids in bacteriostatic activity4. Substituent effects on organic reactions, led by the seminal work of Hammett, which gave rise to the “sigma-rho”culture. Taft devised a way for separating polar, steric, and resonance effects and introducing the first steric parameter, The contributions of Hammett and Taft together laid the mechanistic basis for the development of the QSAR paradigm by Hansch and Fujita5.
 In 1962 Hansch and Muir published their brilliant study on the structure-activity relationships of plant growth regulators and their dependency on Hammett constants and hydrophobicity .Using the octanol/water system, a whole series of partition coefficients were measured, and thus a new hydrophobic scale was introduced. The parameter p, which is the relative hydrophobicity of a substituent, was defined in a manner analogous to the definition of sigma.Fujita and Hansch then combined these hydrophobic constants with Hammett’s electronic constants to yield the linear Hansch equation5.
              Below, a chart of Qsar History is given. It is nice and in brief. So it is easy to remember.



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