40 DEOXYPENTOSE NUCLEOPROTEINS AND PROSTHETIC GROUPS 



and several things can be seen in a clarity and illumination that 

 almost distort their significance. But at the same time we have 

 lost our dark-adaptation; and since we all have a tendency to fol- 

 low the light, we have moved into these cosy corners, to the 

 detriment of the rest, which still is, by far, the major part of 

 nature. In pointing this out one runs the risk of being accused of 

 trying to spread darkness. 



As concerns the subject of the present conference, it will 

 become clear that the biological significance of fibrous proteins 

 can best be defined in those instances to which I have referred 

 above as very special, for instance, in muscular contraction or in 

 blood coagulation. With regard to other conjugated proteins, 

 among which must be counted the nucleoproteins, it is their very 

 ubiquity that has made difficult the recognition of their function, 

 unless one is satisfied with the trite assignment of an essentially 

 mechanical task; but this amounts to no more than saying that 

 these proteins are, because they are. What could, of course, be 

 questioned is whether a purely teleological search for "functions" 

 is likely to prove adequate for the future development of our 

 science. While substances and reactions endure, interpretations 

 often perish with unseemly rapidity; and few things have as short 

 a half-life time as the premature assignment of a function. 



One more introductory remark: When speaking of nucleo- 

 proteins as fibrous proteins, one must specify that this desig- 

 nation refers principally to the deoxypentose nucleoproteins, 

 though some fibrous pentose nucleoproteins are known. Further- 

 more, there is little indication that the carrier proteins themselves 

 are fibrous. This character is conferred on the conjugated protein 

 by the shape of the prosthetic group it contains, namely, the 

 deoxypentose nucleic acids. And, strictly speaking, why these 

 nucleic acids, or for that matter many other macromolecules of 

 natural occurrence, exist as fibers of so marked an anisometry 

 cannot yet be explained satisfactorily on chemical grounds. 



In the following pages a brief survey of the chemistry of those 

 nucleoproteins that can be classified as fibrous, namely, the 

 deoxypentose nucleoproteins, will be followed by the consider- 



