Chemistry and Biochemistry at Low Temperatures 179 



such as enzymes are soluble in some non-aqueous solvents and that a few 

 enzymes can be recovered with virtually their full potency. Since some of the 

 solvents have melting points below that of water they can be utilized for investi- 

 gations of solutions of proteins at relatively low temperatures. It appears 

 entirely possible that had the solution process been carried out at lower tempera- 

 ture a larger fraction of the enzymes would have been recovered without 

 deterioration. Indeed it may prove fruitful to undertake studies at low tempera- 

 tures of the first stages of reactions which are toxic at ordinary temperatures 

 since the toxic substances may be removed at temperatures so low that httle 

 permanent injury is done to the enzyme or organism. 



In analogy with the dissolution of finely divided chlorophyll and iodine 

 by solvents at low temperatures it is to be expected that at low temperatures 

 heterogeneous reactions are also possible between substances in solution and 

 biological materials having high specific areas. Ready-made for such reactions 

 with solutions seem sections of tissue with water removed by freeze-drying. 

 Likewise Becquerel's procedure of removing water by pumping at room 

 temperature would prepare material for reaction at low temperature. Some 

 of the reactions with the surfaces constitute a generalized staining. Many 

 staining processes are acid-base reactions and would be expected to be rather 

 rapid at low temperatures. As has been remarked, molecular steric factors are 

 as a rule more specific at the lower temperatures in general; hence finer dis- 

 criminations between structures within the surfaces are to be anticipated. 



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