Introduction: 4-hydroxyethyl piperazine ethosulfonic acid (HEPES) is an important hydrogen ion buffer, which has a good buffer ability in the pH range of 6.8 to 8.2, and can control a constant pH for a long time. Using a concentration of 10 ~ 50mmol/L, the general culture medium containing 20mmol/L 4-hydroxyethyl piperazine taurine can have a good buffer capacity, and has no toxic effect on cells. Application: HEPES (4-hydroxyethyl piperazinethesulfonic acid) is a non-ionic amphoteric buffer with high polarity, and is inert to a variety of chemical reagents and enzymes. It does not participate in and interfere with the process of biochemical reactions, and has no inhibitory effect on enzyme chemical reactions. Therefore, it can be used specifically for the research of proteins and enzymes that are highly volatile and ph-sensitive to organelles and very volatile. Buffer solution preparation: (1)hepes buffer can be directly added to the prepared culture medium according to the desired concentration, and then filtered to remove bacteria. 2.38 g HEPES was added to each 1000ml of culture medium, the pH was adjusted to 7.2 with lNNaOH after dissolution, and the bacteria were removed by filtration before use. At this time, the concentration of HEPES was 10mmol/L. (2) 100x storage solution (lmol/L) could also be prepared. Before use, 99ml culture solution was added to lml storage solution, and the final concentration was 10mmol/L. lmol/L (100x) hepes buffer was prepared as follows: 23.8gHEPES was dissolved in 90ml double distilled water, the pH was adjusted to 7.5-8.0 with lNNaOH, and then the water was fixed to 100ml, filtered to remove bacteria, divided into vials (2ml/ bottle), and stored at 4�ºC or -20�ºC. Purpose: 1.Biological buffer; Reaction buffer, prehybridization buffer and hybridization buffer for isolation and analysis of RNA nuclear fraction; For RNA with T4RNA 2.Molecular biology grade is used for RNA3' -end labeling with T4 RNA ligase 3.Cell-cell adhesion, short-term cell aggregation culture, cleaning of tissue and cell buffer