CHEMICAL PROPERTIES 



735 



groups are modified, since one may say that the Cl~ ions are competing 

 with the SH groups for Hg++; this affects the dissociation constants for 

 R — S — Hg+ and R — S — Hg — S — R complexes (see page 740). In the sec- 

 ond place, the penetration of the inhibitor into cells will depend on the rel- 

 ative concentrations of these complexes. A few investigators have realized 

 the implications of such complexes and have attempted to take into ac- 

 count the equilibria under their experimental conditions. Jowett and Brooks 

 (1928) calculated the relative concentrations of the complexes in a 0.2 milf 

 solution of HgClg in Locke's medium in a study of the effects of HgClg on 

 tissue glycolysis and respiration, and concluded that the dominant pene- 

 trating species is HgClg, although they were uncertain as to the form ef- 

 fective on the enzymes. Barnes and Stanbury (1948) realized that Hg++ is 

 extremely low in sea water in their investigation of the toxic actions of 

 HgClg on a copepod, and assumed that the prevalent species were HgClg" 



100 



1000 



mM 



Fig. 7-2. Fraction of Hg in various forms in acid medium with varying Cl" 



concentration. The figures at the top give the concentrations of Hg++ and 



HgCl+ at selected Cl~ concentrations. 



and HgCl4=. Green and Neurath (1953) likewise discounted the importance 

 of Hg++ in the inhibition of trypsin in a medium containing 10 mikf CI". 

 In order to facilitate estimation of the relative concentrations of the com- 

 plexes in a narrower range of Cl~ concentration as commonly used in inhi- 

 bition studies. Fig. 7-2 is presented. However, before considering these com- 

 plexes further, it will be necessary to discuss their so-called hydrolysis in a 

 pH range around neutrality. 



