Macromolecules in tissues

This procedure has been developed for quantification of the three types of macromolecules in tissue extracts, where other hiomolecules are also present. Small dissolved amounts of DNA, RNA, or protein, especially when no material should be consumed and no interfering substances are in the solution, maybe estimated by UV photometry, but a discrimination between DNA and RNA is impossible by reading absorbencies (cf. Protocol 1.2.5). 

Only lysine residues on the exterior of the protein molecule are thought to react and these usually account for 40-60% of the total lysyl residues.29 Formalin does not precipitate proteins and only slightly precipitates other components of the cell it is also a good fixative for complex lipids but has no effect on neutral fats and neither preserves nor destroys adipose tissue. Formalin also traps carbohydrates because it preserves proteins so that they hold glycogen, which is otherwise readily leached from the cell. Another advantage of the compound is that it does not produce large bands that obscure the major bands associated with the macromolecules in tissue samples. Furthermore formalin is inexpensive and available in most laboratories. 

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