Chapter 29 

 Deoxyribonucleic Acids as Macromolecules 



C. L. Sadron 



University of Strasbourg and The Center of Research 

 on Macromolecules, Strasbourg, France 



I. Introduction 1 



II. A Brief Survey of the General Principles of the Determination of Weight, 



Shape, and Dimensions of Large Molecules in Solution 2 



1 . Hydrodynamical Methods 3 



2. Optical Methods 6 



III. DNA Particles in Dilute Solutions 15 



1. The Effect of Inter- and Intramolecular Interactions: Rigidity of DNA 

 Particles 16 



2. Light Scattering in DNA Solutions 19 



3. Hydrodynamical Methods 30 



IV. Conclusions 33 



I. Introduction 



One knows that it is possible through proper means to extract from the 

 cell nucleus a substance called deoxyribonucleic acid (DNA) which plays 

 a prominent role in the fundamental processes of life. The extraction is 

 performed by means of physicochemical operations that can vary, accord- 

 ing to the authors, either in the principles themselves (Hammarsten, Signer, 

 and Schwander, Sevag, Butler, etc.), or in minor details (Vendrely, 

 Pouyet). 



The result is a dispersion of the substance in an aqueous solvent of a 

 given pH at a given concentration in an electrolyte such as NaCl. The 

 problem then is to describe the dispersed particles as individuals. We shall 

 see that these particles can be considered macromolecules or sometimes as 

 aggregates of macromolecules which can be separated into their constit- 

 uents. 



In the case of DNA — as it is in general — the complete knowledge of a 

 given macromolecule implies two types of notions. 



First, we need to know the chemical composition of the substance as 

 well as the relative position of the atomic groups which it contains. 



Second, we have to know the weight as well as the shape, configuration, 

 and dimensions of the macromolecule. For that purpose we have to use 



1 



