The conference on "Chemical Structure-Biological Activity: Quantitative Approaches" was held in Prague, Czechoslovakia, on June 27-29, 1973. It took place under the auspices of the J .E. PurkynC! Czechoslovak Medical SOciety, the Czechoslovak Chemi­ cal SOciety, and the International Society of Quantwn Biology (Organizing Commit­ tee: A. David, Chairman; M. Tichy, Secretary General; K. Bo~ek, J. Kopeck~·, R. Zahradnik). This volume contains the lectures and communications presented at the conference. There has been an ever increasing interest, especially during the last eight years, in the study of the quantitative relationships between the chemical structure of substan­ ces and their biological activity (QSAR - quantitative structure-activity relationships). One of the reasons for this increasing interest has been the desire to fmd ways of estimating the quantitative characteristics of a given biological activity as well as to shorten time and reduce the costs of research into optimally active compounds. In contrast to qualitative studies seeking the critical biologically active group, the QSAR approach involves the search for that property, or those properties, which determine the magnitude of the biological effect. Methods of physical chemistry and quantum chemistry appear to be suitable for estimating the quantitative characteristics of the biological activity of different compounds. Forecasting the specific activity of a certain substance by means of theoretical methods is still a matter of future devel­ opment. One of the basic ideas of QSAR studies is to work with a series of chemical compounds thereby enabling the collection and classification of experimental data.

Mathematical Empirical Models of Free Wilson Type, Four-Parameter Equation and Related Topics, Hansch Approach.- Quantum Pharmacology and Quantitative Structure-Activity Relationships: A Brief Review.- On the Parabolic Relationship Between Biological Activity and Hydrophobicity of Drugs: Transport or Protein Binding?.- Quantitation of Chemical and Biological Effects in Steroids by Hansch-Type and Molecular Orbital Calculations.- In Vitro Dissolution Rate as a Parameter in Structure-Activity Studies.- Substructural Analysis in Drug Design.- Stucture-Activity Relationships in a Series of Cinnamic Acids in the Stabilizing Action on Erythrocyte Membrane.- Relationship Between R M Values from Paper Chromatography and Partition Coefficients of Dissociable Compounds.- The Influence of Lipophilicity on the Antibacterial Activity of Rifamycins.- Hansch Analysis in a Series of Substances with Antifungal Activity.- Lipophilicity of Isothiocyanates as a Criterion of their Antimicrobial Spectrum.- The Prediction of New Biologically Active Compounds Using Physicochemical Properties-Activity Relations.- Use of Structure-Activity Relationships to Estimate Toxicity of Inorganic Cations.- Statistical Approaches in Fitting Models.- Some Comments on Possible Types of Analogy Models in the Study of Relations Between Chemical Structure and Biological Activity.- Correlations Between Various Physico-Chemical Properties and Biological Activities.- Correlation Between Physico-Chemical Properties of Chemical Compounds and Indices of their Toxic Action: Use for Prediction.- Relationships Between Some Biological and Physico-Chemical Properties in a Series of Derivatives of Trimepranol [1-(2,3,5-Trimethyl-4-Acetoxyphenoxy)-3-Isopropylaminopropane-2-OL].- Structure-Activity Correlations in aHomologous Series of 2-Substituted Isonicotinic Acid Hydrazides.- Substituent Effects on the Algicidal Activity of Phenyl Thiolacetates.- Interaction of Foreign Compounds with Hemiproteins and Isolated Ferriprotoheme.- Structure-Toxicity Relationships.- Interdependence of Various Types of Pharmacological Activity in Case of Some 4H-Pyrido (1, 2a) Pyrimidine Derivatives.- Structural Dependence of Epileptogenic Action of Penicillins.- Correlations Between Electronic Indices from M.O. Calculations and Biological Activities.- Molecular Orbital Predictions of Properties Influencing Biological Phenomena.- Chemical Structure-Biological Activity Relationships in the Phenoxyacetic Acid Series.- Correlation Between Pharmacological Activity Indices and Quantum Chemical Indices of Some Phenylethylamine Derivatives.- Correlation Between Electronic Indices from Molecular Orbital Calculations and Antiradiation Activity of Thiazolidines.- An Investigation of the Possible Relationship Between Electronic Structure and Antirheumatic Activity in the Hydroxybenzoic Acids.- CNDO/2 Study of the Conformational Properties of the Tricyclic Antidepressants.- Theoretical Studies of Thyroid Hormone Analogs.- A Semi-Empirical Study of the Structural Effects of Ionic Defect Formation in a Model ?-Helical System.- AB INITIO Molecular Orbital Studies in Quantum Biology. Electronic Characteristics of Indole and Benzofuran.- The Application of Hückel Molecular Orbital Calculations to Study of Antituberculotic Activity of Thioamides.- Discussion of the Most Significant Characteristics Used in the Correlations in Terms of a Theoretical Approach.- Calculations of Henry Constants and Partition Coefficients Using Quantum Chemical Approach.- Relationships Among Activity Coefficients, Partition Coefficientsand Solubilities.- Binding of Small Molecules to Sephadex G-10 as a Model Surface. Correlations with Extrathermodynamic Parameters.- Correlations Between Dipole Moments and Biological Activities of Cardiotonic Steroids.