29. DEOXYRIBONUCLEIC ACIDS AS MACROMOLECULES 



27 



M w heated 



12 4 6 8 10 12 hours 9 



Fig. 11. Effect of heat on a solution of DNA not treated with chymotrypsin. M w 

 drops from 14 X 10 6 to 7 X 10 5 after 20 minutes of heating at 75°C. M w remains con- 

 stant ([77] decreasing) for times of heating less than 1 hour. Afterward, the normal 

 process of degradation occurs (sample CV51 in 1 X 10~ 2 molar NaCl). 



TABLE III" 



Molecular Weights of Some DNA Samples Before and 

 After Treatment with Chymotrypsin 



'■ J. Hermans, Jr., Thesis, Leiden (1958); Biochim. el Binphys. Acta 32, 301 f 1959) . 



