Courses : Forest Ecology Lecturer :Frischa Adellia Semester : 4thSemester, 2022/2023 Session Precipitation with TCA ACID Precipitation with TCA (Trichloroacetic Acid) acid is one method commonly used to precipitate proteins from solution. In this method, TCA acid is added to the protein solution, which causes the protein to precipitate and separate from the solution. The deposition process with TCA acid is usually carried out in several stages: 1. Addition of TCA Acid: TCA acid is added to the protein solution in sufficient quantities to achieve the appropriate concentration. TCA acid acts as a protein precipitant because it stimulates the formation of water-insoluble protein-TCA acid complexes. 2. Incubation: After adding TCA acid, the solution is incubated at low or cold temperature for a certain period of time. This allows time for the proteins to settle and form a solid precipitate. 3. Separation: After incubation, the solution is then separated by centrifugation. Insoluble proteins will settle to the bottom of the centrifuge tube, while the supernatant (liquid above the sediment) contains other soluble substances. 4. Washing: The protein precipitate can then be washed with a suitable solution, such as acetic acid in ethanol, to remove contaminants or other substances that may still be attached to the protein. 5. Resuspension: The precipitated protein can then be resuspended or re-dissolved in a suitable solution for further analysis, such as gel electrophoresis or mass spectrometry. TCA acid precipitation is a method commonly used in purifying proteins from biological samples, because it is simple, cheap and efficient. This method can be used to separate proteins from a variety of solutions, including complex solutions such as cell or tissue extracts, and is often considered the first step in many protein purification protocols. The following is an example of the application of precipitation with TCA acid in protein purification: A laboratory is purifying proteins from bacterial cell extracts for further study. Here are the steps they took: 1. Sample Preparation: They start with a bacterial cell extract containing a mixture of proteins from the broken down cells. Such extracts can contain many cellular components, including proteins, nucleic acids, lipids, and other metabolites. 2. Addition of TCA Acid: To precipitate the protein from the solution, they added TCA acid to the bacterial cell extract. TCA acid is used in concentrations sufficient to induce protein precipitation in the form of water-insoluble protein-TCA acid complexes. 3. Incubation and Centrifugation: After adding TCA acid, they incubate the mixture at low or cold temperature for some time. This gives time for the proteins to settle. After incubation, they centrifuged the mixture to separate the protein precipitate from the supernatant. 4. Washing: The protein precipitate is then washed with an appropriate solution, such as acetic acid in ethanol, to remove contaminants or other substances that may still be attached to the protein. 5. Resuspension: The precipitated protein is then resuspended or re-dissolved in an appropriate solution, such as a protein stirrer or buffer solution, for further analysis. With these steps, they succeeded in precipitating and purifying proteins from bacterial cell extracts. The purified protein can then be used for further analysis, such as gel electrophoresis, chromatography, or protein structure studies. The TCA acid precipitation method has helped separate proteins from various other cellular components in samples, enabling more specific and accurate protein analysis.