Chapter 3 

 VITAMIN Bi, 



Page 



I. Nomenclature and Formulas 396 



II. Chemistry 397 



A. Isolation 397 



B. Chemical and Physical Properties 400 



C. Constitution 402 



1. 5,6-Dimethylbenzimidazole 402 



2. l-a-D-Ribofuranosido-5,6-dimethylbenzimidazole 404: 



3. Dg-l-Amino-2-propanol 406 



4. Nature of the Cobalt Complex 407 



5. jNIiscellaneous Degradation Reactions 414 



D. Synthesis 414 



1. Radioactive Modifications 416 



III. Industrial Preparation 417 



IV. Biochemical Systems 421 



A. Vitamin B^ and Nitrogen Metabolism in Animals 421 



B. Vitamin B12 and Thyrotoxicity 422 



C. Vitamin B12 and Liver Function 423 



D. Vitamin B]j and Tyrosine Metabolism 425 



E. Single-Carbon Units 425 



F. Relation of Vitamin B12 to the Metabolism of Choline and Methionine 432 



1. In Chicks. . . ^ 432 



2. In Rats 439 



G. Vitamin B12 and Tumors 443 



V. Specificity of Action 443 



A. Animal and Microbiological Metabolism 443 



B. Human Metabolism 445 



VI. Biogenesis 446 



VII. Estimation 448 



A. Physical 448 



B. Chemical 449 



C. Biological 452 



1. Assay with Chicks 452 



2. Assay with Rats 454 



D. Microbiological 455 



1. Tube Methods for Assay of Vitamin B12 457 



2. Cup-Plate Methods for Assay of Vitamin B12 466 



3. E'sc/jer/c/iza co/j Pad-Plate Method 468 



4. Sample Treatment 470 



VIII. Standardization of Activity 472 



IX. Occurrence in Food 476 



X. Effects of Deficiency 481 



A. Metabolic Aspects and Function of \'itamin B12 in Microorganisms . 481 



395 



