32 Applied Biophysics 



we study the nature of the reactions, but not their dynamic 

 aspects in relation to the Hving system. The so-called "law of 

 homologous series/' which expresses the regularity with which 

 pharmacological activity increases with the length of hydro- 

 carbon chain, is possibly due to the close association of the 

 lipids and enzyme receptors at the site of drug action. The 

 primary role of the structural lipids may be the storage and 

 presentation of drug to the active groups in the enzyme system. 

 The characteristic rise and fall in activity as a series of 

 homologous drugs is ascended, for example, with the maximum 

 pressor activity in the aliphatic primary amines ; antiseptic ac- 

 tivity of the alkyl phenols, ^^ resorcinols -"^ ; and bactericidal and 

 fungicidal activities of alkyl derivatives of o- and /^-chlorphenols 

 investigated by Klarman, Shternov, and Gates,^- may simply 

 be due to some optimal association of the drugs with the struc- 

 tural lipids or lipoproteins, which is consistent with maximum 

 access or presentation of the drugs to the associated enzyme 

 complex. This concept would also explain how the maximum 

 activity in a homologous series of drugs may vary in different 

 tissues and organisms. 



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