886 17. PLANNING AND REPORTING INHIBITION STUDIES 



(2) Present the inhibitions in inhibition studies. It greatly aids the reader 

 if inhibitions are calculated, reported, and averaged if feasible, rather 

 than giving only the experimental data. Of course, the raw data may 

 in certain cases be quite important. The presentation of only rate curves 

 makes it frequently very laborious for the reader to calculate inhibitions 

 and interpret the results quantitatively. 



(3) Express concentrations in molar terms. The concentrations in many 

 reports on inhibitors are given in terms of weight per volume. Such con- 

 centrations are occasionally ambiguous because one doesn't know the 

 salt used or the assumed hydration. Furthermore, it is difficult to compare 

 different reports when the units of concentration are not expressed uni- 

 formly. Another common practice it to state the amount of material in 

 the reaction vessel; e.g., 20 //moles of succinate per vessel, or 3 //moles 

 of ATP in 3.3 ml of the medium. In some cases there is justification for 

 this but usually one wishes to know the molar concentrations. It makes 

 little difference whether the concentrations are given in M, milf or juM, 

 but it must be remembered that these are abbreviations for concentrations 

 and not for actual quantities, which must be written out as moles, milli- 

 moles, or micromoles (//mo.^es). 



(4) Compare the relative potencies of different inhibitors on a molar basis. 

 If several inhibitors are to be compared with regard to their actions on an 

 enzyme or metabolic process, the concentrations producing chosen effects 

 must be on a molar basis rather than a weight per volume basis. This is 

 actually what one does in the determination of different K/s. 



SUGGESTIONS OF A GENERAL NATURE 



(1) Dont use inhibitors without adequate hnmvledge of their properties. 

 One cannot either use inhibitors properly or interpret the results of their 

 actions if one does not understand the nature of the inhibitions and the 

 ranges of the inhibitor actions. In particular it is important to know the 

 specificity as far as is possible. The initial choice of the inhibitors to be used 

 will, of course, depend on such knowledge and there are many examples 

 where more informative data would have been forthcoming if more care 

 had been devoted to the selection of inhibitors. 



(2) Use inhibitors with specific and rational purposes. As in any field of 

 scientific investigation, one should have a good reason for the use of a 

 particular procedure. In many studies involving inhibitors, especially in 

 the characterization of enzymes, it would appear that the inhibitors used 

 are those that happen to be on the shelves and, as a result, the useful in- 

 formation derived is less than one might hope. Naturally there are cases 

 where exploratory testing is necessary because the investigated system is 



