Hydrophobic region of proteins

Polymers of the naturally occurring amino acids alanine, leucine, and methionine all show interactions which depend on the relative directions of the backbones. In contrast, poly(L-norleucine) shows less specific interactions clearly for the hydrophobic regions of proteins to function in a precise manner the natural amino acids are most suitable. 

Polystyrene beads are known for their capacity to bind immunoglobin G globulins nonspecifically, by hydrophobic interaction, so that the immu-nospecificity of the Fab region is preserved. Because of the dipolar nature of the phenyl ring, polystyrene probably represents a surface capable of extraordinary interaction with hydrophobic regions of proteins. 

The second fluorescent stain, which needs mention, is anilinonaphthalene sulphonate (ANS) which does not fluoresce in water. It does, however, fluoresce when dissolve in organic solvents or when it becomes bound to the hydrophobic regions of proteins.The stain is not as sensitive as fluorescamine and the lowest detection limit Is only 20 mg. The method involves incubation of the gels in 3N HCI for about 5 minutes to denature the proteins. After this the gels are incubated in a buffered solution of the stain. If sensitivity is not such a big limitation, i.e., if the quantity of protein separated is high, one may bypass the acid denaturation step. This allows the final recovery of proteins in the active form. 

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