DOUGLAS M. SURGENOR 



which participate in the binding reaction. Similarly, the 

 effect of />H, temperature, and competing substances can be used 

 to deduce certain of the features of the participating groups of 

 the protein. Klotz (19), for example, has suggested that methyl 

 orange and azosulfathiazole interact with albumin through the 

 e-amino groups of lysine. Obviously this suggestion requires 

 amplification in order to differentiate between binding by albu- 

 min and lack of binding by 7-globulin, since both contain 

 appreciable amounts of lysine. The analogy to the enzymes is 

 of course evident, but particularly in the case of albumin 

 because of the wide range of interacting substances, many of 

 which apparently fail to share any common property, attempts 

 to find a rational theory have thus far been fruitless. The 

 frustrating nature of the problem is epitomized by the inter- 

 action of albumin with chloride ions (32). At physiological 

 concentrations approximately six chloride ions are bound per 

 molecule of albumin, but no experimental evidence has been 

 obtained concerning the mechanism of this interaction. 



Defense against Infection 



The study of the various mechanisms by which the organism 

 combats infection has long been a separate and specialized area 

 of investigation which is beyond the scope of this discussion. 

 Some recent developments warrant comment, however, because 

 of their bearing on some of the biochemical aspects of the 

 problem. Recently in the course of investigations on the purifi- 

 cation of the components of complement, Pillemer (29) dis- 

 covered a new factor, intimately involved with the functions of 

 complement, but readily separable therefrom by adsorption on 

 zymosan. Termed properdinj, this new component apparently 

 acts only in combination with complement and magnesium ions, 

 and is essential for the bactericidal and antiviral properties of 

 normal serum. Of even greater interest is the finding that 

 properdin levels dropped sharply following irradiation, whereas 

 complement levels were unaffected or even increased slightly. 



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