SPECIAL PART 



I. Optical measurement of hydrogenation and dehyrogenation 



No one who has not worked in biochemistry before the hydrogentransferring 

 function of nicotinamide was discovered can fully appreciate the significance of 

 a method that is based on the absorption of light by the dihydropyridine nucleo- 

 tides in the near ultraviolet ränge, at 340 ma. It is no exaggeration to say that 

 this method has reduced the time previously required for detecting and measuring 

 the most important metabolic reactions to about onehundredth. The method is 

 not limited to hydrogenation and dehydrogenation but can be extended to degra- 

 dations, phosphorylations, and all processes that can be coupled in any way with 

 hydrogenation or dehydrogenation. Paper {2) in this collection illustrates the 

 foregoing for fermentation reactions. 



If c is the concentration of dihydronicotinamide, d the path of light of wave- 

 length 340 m\i, and ß the absorption constant of the dihydronicotinamide, then 



In — — = ß X c X d 

 i 



If we express c in micromoles per cubic centimeter and d in centimeters, the 

 dimension of ß becomes Square centimeters per micromole. The numerical value 

 ofjS 



ß = 14 



cm- 



//mole 



is one of the most important and most frequently used quantities in biochemistry. 

 If this value is known, one may immediately derive from it, by means of the 

 following expression, the number of micromoles of hydrogen per cubic centimeter 



20 



that were transferred in any one liquid, provided has been measured : 



z'o 



I /// 

 1 

 Ac 



ß x d 



//mole 



cm- 5 



For instance, if — = 2 and d = - 1 cm, then 



i 



■Un — 



i 0,7 



ß x d 14 



//mole 



crrr 



from which it may be seen that the optical method is very sensitive, approximately 

 10 times as sensitive as our biological manometry. 



The directions for carrying out this method have not changed since 1935-, 

 since the function and the UV-bands of dihydronicotinamide were discovered. 

 However, this method did not become generally accessible until our photoelectric 

 cell was replaced by the spectrophotometer of Beckman and Zeiss-Oberkochen 

 and until the firm of Böhringer began to market pure metabolic enzymes. 



