FOREWORD 



The past fifty years have seen an astounding increase in our understanding 

 of the nature of the physical world. Only fifty years ago was it discovered 

 that an atom consists of a small heavy nucleus and some electrons surround- 

 ing the nucleus. A tremendous amount of knowledge has been gathered dur- 

 ing this period of fifty years about the structure of atoms and of simple 

 molecules. 



It is now becoming possible to extend the experimental techniques that 

 have been applied to simple molecules to the more complicated molecules 

 that are found in living organisms. Some information has already been gath- 

 ered about the structure of the simplest proteins, but the job of making 

 a complete three-dimensional structure determination for a protein molecule 

 has not yet been carried through to completion. Nevertheless, it is evident 

 that this job will soon be done. During the past year great progress has been 

 made by John Kendrew of Cambridge University in the determination of 

 the positions of the atoms in the molecule of myoglobin, and the techniques 

 of X-ray diffraction that he and other investigators in the field of protein 

 structure are now applying can be expected to lead in another decade or 

 two to the complete determination of the structure of many globular 

 proteins. 



The enzymes constitute a class of protein molecules of extraordinary 

 significance. Just as deoxyribonucleic acid may be said to be the substance 

 that we need to understand if we are to know in its atomic detail the mech- 

 anism by means of which organisms reproduce themselves, so are the 

 enzymes the molecules that we must understand to know how organisms 

 carry on their metabolic activities. 



No one knows the precise molecular structure of any enzyme and the 

 exact way in which the enzyme carries on its characteristic function of 

 catalyzing chemical reactions. During the next fifty years we can be assured 

 that this knowledge will be gained, in large part probably through structure 

 determinations made by the X-ray diffraction technique. Nevertheless, even 

 though detailed structural information is still lacking, a very great deal has 



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