Magnetic bead extraction of nucleic acids is an efficient and widely used experimental technology, mainly used to isolate and purify DNA or RNA from biological samples. This method is based on the specific binding between the magnetic beads and the target molecule, and uses the action of a magnetic field to achieve the extraction of nucleic acid. The magnetic bead method is not only simple to operate, but also has high extraction efficiency. It is one of the common nucleic acid extraction techniques in modern molecular biology experiments.
1. Structure and Characteristics of Magnetic Beads are the core components of nucleic acid extraction of magnetic bead method, usually composed of internal magnetic substances (such as Fe3O4, γ-Fe2O3) and external cladding. Among them, magnetic substances enable the magnetic beads to gather and disperse under the action of an external magnetic field, which facilitates operation; while the cladding layer determines the binding ability of the magnetic beads to nucleic acids. The cladding layer usually includes a SiO2 layer and specific functional groups (such as amino, carboxyl, hydroxyl, etc.) modified on the surface of the silicon layer, which are capable of interacting with nucleic acid molecules.
2. Principle of binding between nucleic acid and magnetic beads 1. Ion exchange effect: Under appropriate buffer conditions, the phosphate groups in the nucleic acid molecule bear negative charge. Functional groups (such as amino groups) modified on the surface of the magnetic bead can be protonated at a specific pH value and have a positive charge. Through electrostatic attraction, the phosphate groups of the nucleic acid molecule bind to the cations on the surface of the magnetic beads. 2. Hydrogen bonding: The bases in nucleic acid molecules, hydroxyl groups on ribose or deoxyribose can form hydrogen bonds with the functional groups on the surface of the magnetic beads. This hydrogen bonding function plays an auxiliary and stable role in the binding process of nucleic acids and magnetic beads. 3. Hydrophobic effect: The nucleic acid molecule itself has a certain hydrophobic region, and some hydrophobic groups on the surface of the magnetic bead can interact with the hydrophobic part of the nucleic acid. In the buffer environment, this hydrophobic effect helps the nucleic acid molecules approach the surface of the magnetic beads, thereby achieving tight bonding through other stronger forces such as ion exchange and hydrogen bonding.
3. Steps for nucleic acid extraction by magnetic bead method 1. Lys the cells and release nucleic acids: lyse the cells in the sample (such as blood, tissue, cell culture medium, etc.) to release the nucleic acid into the solution. Lysates usually contain components such as detergents (such as sodium dodecyl sulfate, SDS), proteases (such as protease K), and salts to destroy cell membranes and nuclear membranes, degrade proteins bound to nucleic acids, and maintain appropriate ionic strength. 2. Binding of magnetic beads to nucleic acid: Add magnetic beads to the lysate containing nucleic acids, and adjust the pH value, ionic strength and other conditions of the buffer, so that the functional groups on the surface of the magnetic beads can effectively bind to nucleic acid molecules. Generally, it can achieve better combination effect by shaking at room temperature for several minutes (such as 5 to 10 minutes). 3. Wash and remove impurities: After the nucleic acid is combined with the magnetic beads, impurities need to be removed through the washing step. The washing solution is generally a solution containing a specific concentration of salt and buffer components. It can wash away impurities such as proteins, polysaccharides, salt ions and other impurities in the lysate without destroying the binding of nucleic acid-magnetic beads. The washing process is usually repeated multiple times (such as 2 to 3 times) to ensure that impurities are fully removed. 4. Elution of nucleic acid: By changing the conditions of the buffer (such as pH, ionic strength, etc.), the nucleic acid is removed from the surface of the magnetic beads. The eluent is generally low-salt buffer or water. Place the magnetic bead-nucleic acid complex in the eluent, and adjust the pH value of the eluent and other conditions to make the nucleic acid eluent eluent eluent eluent. The eluted nucleic acid solution can be used in subsequent molecular biology experiments, such as polymerase chain reaction (PCR), gene sequencing, etc.
4. Advantages of nucleic acid extraction of magnetic bead method 1. High purity: nucleic acid extraction of magnetic bead method can effectively remove impurities through multiple washing steps and improve the purity of the extracted nucleic acid. 2. High recovery rate: The binding of magnetic beads to nucleic acids is specific and efficient. Under suitable conditions, most nucleic acids can be adsorbed by magnetic beads and effectively recovered. 3. Automation potential: Magnetic beads can be easily separated and transferred under the action of magnetic fields, making it easy to automate the extraction of nucleic acids of magnetic beads. This has significant advantages in large-scale genetic screening or clinical diagnostic laboratories.
The principle of extracting nucleic acids by magnetic bead method is based on the specific binding effect of magnetic beads and nucleic acid molecules, and the efficient extraction of nucleic acids is achieved through cleavage, binding, washing and elution. This method has the advantages of high purity, high recovery rate and easy automation, and is widely used in biomedical research and clinical diagnosis.
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