Cetyltrimethylammonium bromide or hexadecyltrimethylammonium bromide (CTAB), is a cationic detergent commonly used in molecular biology to break down cell walls and membranes, making it easier to isolate nucleic acids. The chemical structure of CTAB consists of a long hydrophobic alkyl chain (hexadecyl group) attached to a positively charged nitrogen atom (trimethylammonium group), with a bromide ion as the counterion. When CTAB is dissolved in water, the molecules disperse. Each molecule has a hydrophobic (water-repelling) tail and a hydrophilic (water-attracting) head. As the concentration of CTAB increases, the molecules start to aggregate. When the concentration reaches a certain threshold, known as the Critical Micelle Concentration (CMC), the surfactant molecules spontaneously form micelles. Chemical structure and hydrophobic and hydrophilic region sectors of a strong cationic detergent CTAB and micelles. CTAB exists as individual monomers below CMC while as micelles above CMC.
CTAB is widely used to isolate DNA from a variety of biological samples such as bacteria, fungi, insects, mussels, and plants. Traditional CTAB protocols typically require the homogenization of plant samples in extraction buffer prior to centrifugation to pellet debris and polysaccharides. The supernatant is then extracted using chloroform, and DNA is precipitated with alcohol. The isolated DNA is typically very clean.
