Fluorescence-based analysis of cellular protein lysate arrays using quantum dots.

Reverse-phase protein microarrays (RPPMAs) enable heterogeneous mixtures of proteins from cellular extracts to be directly spotted onto a substrate (such as a protein biochip) in minute volumes (nanoliter-to-picoliter volumes). The protein spots can then be probed with primary antibodies to detect important posttranslational modifications such as phosphorylations that are important for protein activation and the regulation of cellular signaling. Previously, we relied on chromogenic signals for detection. However, quantum dots (QDs) represent a more versatile detection system because the signals can be time averaged and the narrow-emission spectra enable multiple protein targets to be quantified within the same spot. We found that commercially available pegylated, streptavidin-conjugated QDs are effective detection agents, with low-background binding to heterogeneous protein mixtures. This type of test, the RPPMAs, is at the forefront of an exciting, clinically-oriented discipline that is emerging, namely tissue or clinical proteomics.