Target site, specificity labeling

Some problems with FCS technology concern the fluorescent label. Data collection is possible only if the label does not interfere with the structure of the labeled molecule or the binding of the target to the ap tamer. Also, the label should be site-specific, because molecules that are labeled at different positions may have different binding properties. Another problem concerns the molecular weight difference between the free and complexed molecule, which should be sufficient for... 

To examine the phosphorylation of the myc-tagged wild-type 5-HT3A receptor subunits from the guinea pig, stably transfected HEK 293 cells were meta-bolically labeled with [32P]phosphoric acid (158). It was demonstrated that both splice variants of the 5-HT3A receptor subunit were phosphorylated. Moreover, site-specific mutagenesis revealed that phosphorylation occurs at Ser409, a potential target of PKA. 

The special problems associated with labeling a specific target site in a heterogeneous mixture of proteins such as that which exists in cells can be examined in terms of the specificity equation (see Equation 35). In terms of specificity of labeling, the essential difference between label-... 

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