CHAPTER 3 



The Reactions of Fixatives with 

 Proteins 2. The Chemical Changes 



The most familiar fixative substances will be considered one by 

 one, from all points of view connected with their use as fixatives, 

 in chapters 5 and 6 (pp. 89 and iii). Their chemical composition 

 and the ions they form when dissolved in water wdll be mentioned 

 there. To prevent unnecessary repetition, this information will 

 not be given in the present chapter. 



It is important to explain certain terms and conventions that 

 will be used in this chapter and throughout the rest of the 

 book when reference is made to the chemical structure of pro- 

 teins. 



A protein has two constituent elements, which will be called the 



NH 

 HCH glycine 





NH 



I 

 HC.CH.,SH cvsteine 



r° 



NH 



HC(CH2)4NH2 lysine 



c=o 



A small part of a protein chain. The atoms of the 

 backbone are shown in bold letters. 



backbone and side-groups. The backbone is made up of those parts 

 of the amino-acids that are the same in all. These are repeated 



44 



