Protein extraction and purification seeks to isolate a single type of protein from a mixture in order to determine its function, structure, and interactions. Plant cells are disrupted (lysed) using physical or chemical methods. Extracted proteins can then be used for procedures like Western blotting, 2D gels, and enzyme analysis. Sigma-Aldrich offers a variety of reagents and kits for effective plant protein extraction, considered to be the most critical step of proteomic analysis.Various methods are used to extract specific proteins from plant tissues for downstream proteomic applications. One extraction technique isolates intact chloroplasts from plant leaves. The procedure involves mechanical cell wall and cell membrane breakage, removal of cell debris and leaf tissue by filtration, collection of total cell chloroplast fraction by centrifugation, and the separation of intact chloroplasts from broken chloroplasts. Sigma-Aldrich has a variety of products designed to help researchers extract proteins efficiently and without degradation.