Vlll CONTENTS 



V. Controlling Mechanisms of Enzyme and Protein Synthesis ... 128 



A. Introduction 128 



B. Genetic Controls 129 



C. Some Nutritional Phenomena 135 



D. The Induced Biosynthesis of Enzymes 137 



VI. Biochemical Mechanisms of Polymer Formation 151 



A. Phosphate Transfer 153 



B. Polysaccharide Biosynthesis 163 



C. Phospholipid Synthesis 167 



D. Mechanisms of Peptide Synthesis 168 



E. The Biosynthesis of Nucleic Acid Intermediates 176 



F. Biosynthesis of the Nucleic Acids 183 



VII. Problems of Polymer Duplication 191 



A. DNA DupUcation and Partition 192 



B. The Transfer of Biological Information 196 



VIII. Conclusion 202 



Keferences 203 



in. The Physical Properties of Infective Particles by Howard K. 



SCHACHMAN AND RoBLEY C. WiLLIAMS 223 



I. Introduction 224 



II. Physical Methods 227 



A. Hydrodynamic and Thermodynamic Methods 227 



B. Optical Methods 271 



III. Application of Physical Methods to Virus Studies 297 



A. Homogeneity and Purity as Related to Virus Identification 297 



B. Identification of Physical Particles as Infective Agents .... 299 



C. Physical Properties of Well-Studied Viruses 303 



References 323 



IV. Quantitative Relationships between Virus Particles and Their 



Functional Activity by Carlton E. Schwerdt 329 



I. Introduction 329 



II. Titration of Virus Infectivity 330 



A. Assay Based on All-or-None Response 331 



B. Assay by Local Lesion Count 333 



C. Factors Affecting Virus Infectivity Titrations 337 



III. Methods of Determining Total Virus Particle Concentrations 339 



A. Direct Methods: Electron Microscopy 339 



B. Indirect Methods 342 



IV. Relationships between Total Particle Count and Biological 

 Function 346 



A. Initiation of Infection by a Single Virus Particle 346 



B. Observed Ratios between Virus Particle Count and In- 

 fectious Units 349 



