from the histocheniical standpoint. Implicit in considération of substrate 

 design should be molecular geometry as well as the présence of certain 

 structural features. Among thèse the présence of peptide bonds, saturated 

 ring structures, halogen, azo, and quinone groupings hâve been shown 

 to enhance substantivity. The value of the aforementioned groups is 

 évident in the case of the post-coupling and fluorescent substrates. 



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