Membrane arrays offer a multiplex approach to assaying protein expression. They are membrane-based assays that allow simultaneous screening of multiple proteins in a sample. Membrane antibody arrays are commercially available from many suppliers and can be constructed to assess less than 10 to hundreds of proteins in a pathway or biological system of interest. The arrays are convenient for assaying expression of proteins involved in inflammation, angiogenesis, apoptosis, cell signaling, and other cellular processes.
A membrane antibody array is a sandwich-style immunoassay, similar to an ELISA. The difference between the two is that the capture antibody is spotted on a membrane, instead of the bottom of the well of a dish for ELISA. The sample is applied to the membrane and any proteins that become bound to the capture antibodies are detected with a second set of labeled antibodies. The arrays are usually imaged using chemiluminescent signal.
Similarly, dot blots can be imaged and analyzed using chemiluminescence or fluorescence detection. A dot blot is a Western blot in which the sample is spotted onto a membrane. Dot blots speed the process of asking whether a protein is present in a sample by skipping the electrophoresis and transfer steps of a traditional Western blot. This facilitates the high-throughput screening of multiple samples but at the cost of losing information about protein size and the ability to differentiate noise from specific bands.
Analysis software is also able to help you analyze your membrane and antibody arrays. For this, Azure Biosystems offers AzureSpot Pro, a software which includes an analysis module to facilitates the analysis of membrane antibody arrays and dot blots, as well as plate-based assays. This module assists with presence/absence detection and normalization.
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Chemiluminescent detection (Figure 1) depends on an enzymatic reaction so timing and the amount of both enzyme and substrate used have important effects on data quality.