Solvent Perturbation Fluorescence Immunoassay Technique

The use of fluorescent dyes to label analyte In llgand binding assays affords the posslbllty of convenient, homogeneous assays. The homogeneous response depends upon a significant difference In a fluorescent property of bound compared to free labeled analyte. We have found that dodecyl sulfate quenches the emission Intensity of free fluorescein labeled gentamycin without Influencing the emission Intensity of labeled gentamlcln bound to gentamlcln antibody. This preferential quenching by detergent Is demonstrated to serve as the basis for a homogeneous fluorescence Immunoassay for gentamlcln requiring only simple Intensity measurements. The method may be used to measure other analytes when It can be demonstrated that the perturbing agent (In this case, detergent) preferentially Influences the intensity of free labeled analyte. This preferential perturbation may be assured by judicious choice of perturbing agent and labeling fluor so that the Interaction between labeled analyte and the perturbing agent occurs with the analyte moiety and not with the fluor moiety.