Immunofluorescent labeling of proteins in cultured cells with quantum dot secondary antibody conjugates

Our understanding of the level and distribution of gene and protein expression in cells is a key component of modern cell biological and medical research. Detecting intracellular proteins with labeled antibodies or genes with labeled oligonucleotide sequences by fluorescence microscopy requires fixation of the target molecule in its natural distribution and the penetration of the probe to the target. This typically involves chemical fixation followed by a detergent treatment that renders the cell membrane permeable to a labeling antibody. The advantages of using quantum dots (QDs) over organic dyes to detect expression, such as high brightness, stability, and simplified multiple target labeling has been described in previous publications. However, QDs are structurally larger than organic dye probes and require different fixation and permeabilization conditions for optimum labeling. In the chapter, we describe several protocols for labeling proteins in nuclear, cytoplasmic, and membranous compartments with QD conjugates.