DESOXYRIBONUCLEIC ACID 



98 



DEUTERIUM 



Biol. Chem. 1940, 133, 593-604) set up 

 10 8" X 1, pyrex tubes as below. 



1 3 ml. DNA extract from aliquot 1 + 6 ml. blank 



Dische 



2 3 ml. DNA extract from aliquot 2 + 6 ml. blank 



Dische 



3 3 ml. DNA extract from aliquot 3 + 6 ml. blank 



Dische 



4 4 ml. DNA extract from aliquot 4 + 6 ml. blank 



Dische 



5 3 ml. DNA extract from aliquot 1 + 6 ml. Dische 



reagent 



6 3 ml. DNA extract from aliquot 2 + 6 ml. Dische 



reagent 



7 3 ml. DNA extract from aliquot 3 + 6 ml. Dische 



reagent 



8 3 ml. DNA extract from aliquot 4 + 6 ml. Dische 



reagent 



9 3 ml. 6% perchloric acid + 6 ml. blank Dische 

 10 3 ml. 6% perchloric acid + 6 ml. Dische reagent 



Heat tubes 10 minutes at 100°C., cool 

 to room temperature and read optical 

 density (D) at GOO m/i. Read unknowns 

 against corresponding blanks set at zero, 

 as below: 



5 10 



C D C D — = Corrected DNA concentration of 



1 ® tube 5 



a in 



Q J) Q J) = Corrected DNA concentration of 



tube 5 against tube 1 as a blank 

 tube 6 against tube 2 as a blank 



tube 7 against tube 3 as a blat 



(°t) 



tube 8 against tube 4 as a blank ( D — I 



/ 10\ 

 tube 10 against tube 9 as a blank 1 D — I 



The nucleic acid concentrations (C) 

 corresponding to the five D readings 

 are then obtained from a standard 

 curve. The latter is constructed in 

 the usual manner from at least 20 points, 

 by subjecting various concentrations of 

 a standard DNA to the Dische pro- 

 cedure and plotting the resulting D 

 readings against these concentrations. 

 The solvent (O.OIN NaOH or hot 6% 

 perchloric acid) plus Dische reagent 

 is used as a blank. Beer's law should 

 be closely obeyed in the useful range. 



The DNA concentration correspond- 

 ing to the D reading of tube 10 against 



tube 9 ( C D^ ) is the correction for 



color developed by the reagents alone 

 and is subtracted from the concentra- 

 tions found for the unknowns. 



tube 6 



etc. 



The volumes of DNA extracts are 

 measured and the total DNA per aliquot 

 thus found. This value is divided by 

 the number of nuclei per aliquot (ho- 

 mogenate nuclei minus supernate nu- 

 clei) to obtain the average DNA content 

 per nucleus, most conveniently ex- 

 pressed in fifig (mgm. X 10 — 9). This 

 will usually range from 5-10 nixg., de- 

 pending upon the purity of DNA em- 

 ployed in constructing the standard 

 curve. The values of the four aliquots 

 should agree within 5%. 



If an efficient means could be found 

 of separating the various nuclear types 

 of a given tissue, the value of this 

 technique would be greatly enhanced. 

 A method for determination of De- 

 soxyribonucleic Acid in isolated nuclei 

 of tumor cells (Dounce, A. L., J. 

 Biol. Chem., 1943, 151, 235-240). 

 Same as DNA and Thymonucleic 

 Acid. The structure of this acid in 

 relation to the cytochemical significance 

 of methyl green-pyronin staining is 

 carefully considered by Vercauteren, 

 R. , Enzymologia, 1950, 14, 134-140. See 

 Nucleic Acid. 



Destin's fixative. 1% aq. chromic acid, 99 

 cc; formalin, 6 cc; glacial acetic acid, 

 2 cc. After standing for a few days it 

 becomes green when it can be used. 



Detergents, see discussion of cutaneous 

 detergents by Lane, C. G. and Blank, 

 I. H., J.A.M.A., 1942, 118, 807-817. 

 See Aerosol. 



Deuterium is heavy hydrogen. It is an iso- 

 tope having atomic weight of 2.0135 and 

 the symbol H^. Schoenheimer, R., 

 Harvey Lectures, 1937, 32, 122-144 em- 

 ployed deuterium combined with oxy- 

 gen as heavy water H|0 to mark fatt}'- 

 acids. In his experiments on mice, 

 held on a carbohydrate diet plus heavy 

 water the fatty acids of the body are 

 replaced by new fatty acids containing 

 deuterium. The rate of replacement of 

 fatty acids can therefore be deter- 

 mined. For further experiments along 

 this line see Symposium on Interme- 

 diate MetaboUsm of Fats. Biological 

 Sj'mposia Lancaster: Jaques Cattell 

 Press, 1941. Leading references on 

 deuterium: Cope, O., Blatt, H. and 

 Ball, M. R., J. Clin. Invest., 1943, 22. 

 111-115; Flexner, L. B., Gellhorn, A. 

 and Merrell, M., J. Biol. Chem., 1942, 

 144, 35-40; Stern, K. and Dancey, T. E., 



