viii CONTENTS 



B. Ribonucleic acids and protein synthesis 63 



1 . Plurality and Metabolic Heterogeneity of cellular RNAs 63 



2. Metabolism of RNA and protein synthesis 66 



3. Importance of the structural integrity of RNAs 70 



(a) Effects of ribonuclease 70 



(b) Modification of RNAs by analogues of purines and 



pyrimidines 73 



(c) Summing up 78 



4. RNA as the genetic messenger 79 



(a) Do RNA molecules carry genetic information? 80 



(b) Is cytoplasmic RNA made in close contact with DNA? 83 



(c) Where is the genetic messenger? 89 



5. Concluding remarks 90 



Chapter IV. Chemical Pathways of Protein Biosynthesis 



A. Energy requirement 92 



B. The activation of amino acids 96 



1. Amino acid activation enzymes 96 



2. Transfer RNA 102 



C. Other factors involved in protein synthesis 109 



D. The sequential condensation of amino acids into polypeptides 112 



1. Are there free peptide intermediates? 113 



2. Are polypeptides made on a template? 117 



E. Formation of the protein molecule 



(a) Folding 122 



(b) Disulphide bridges 123 



(c) Association of polypeptides 123 



(d) Further transformations 123 



(e) Integration of proteins into structures 124 



Chapter V. Regulation of Protein Synthesis 



A. Enzymic adaptation 126 



1. Induced synthesis of enzymes in micro-organisms 127 



2. Repression of enzyme synthesis in micro-organisms 130 



3. Mechanisms of repression and induction 131 



4. Induced transformation of an enzyme 137 



5. Permeases and enzyme synthesis 138 



6. Enzymic adaptation in animal tissues 139 



B. Non-mendelian hereditary factors in enzyme synthesis 141 



C. Changes in protein synthesis during differentiation 150 



D. The formation of antibodies 156 



Subject Index 197 



Author Index 207 



