Protein microarray technology

Following the completion of the human genome sequencing project, well-established DNA microarrays and sophisticated bioinformatic platforms now allow scientists to take a global view of biological systems. The different physiological states of cells correlates with different cellular protein expression and with differences in protein function–known as the cellular proteome. The interactions between a cell and its environment are influenced by several parameters in parallel (e.g., cell signaling molecules, cell–cell and cell–matrix interactions). Cellular processes controlling and defining the physiological state of a cell regulate messenger RNA (mRNA) and protein expression, control protein modification and localization and therefore regulate protein function (FIGURE 1) [1]. Nowadays, several different technologies are applied to analyze the complex and highly dynamic protein content of biological systems. None of these technologies have the potential to deal with the whole complexity and the huge dynamic range (107) of protein expression in cells [2]. The most widely used separation technology for the simultaneous examination of large numbers of proteins is 2D polyacrylamide gel electrophoresis (PAGE), which suffers from low sample throughput, a small dynamic detection range and severe difficulties in the analysis of hydrophobic, small and very basic or acidic proteins. Multidimensional chromatography approaches (e.g., multidimensional protein identification technology) and different affinity capture chromatographic methods (isotope-coded affinity tagging, metal chelates) are used as alternatives to 2D-PAGE for the separation of analytes and reduction of complexity prior to mass spectrometry-based protein identification [3,4]. But despite these very impressive developments in proteome analysis technologies, there is still an urgent need for alternative tools that allow a global view into the proteome. Microarray technology has the potential to monitor complex intracellular gene and protein expression and to simultaneously study the interaction between proteins and a large number of potential interaction partners (FIGURE 1).