HEPES buffer is 2 - (4 - (2-hydroxyethyl) piperazine) ethanesulfonic acid, CAS 7365-45-9. This buffer is usually used in biochemical experiments to adjust the pH value of the reaction system, such as virus preservation solution or cell preservation solution.
There are two types of HEPES buffer on the market: powder reagent and solution reagent. The concentration of HEPES solution is 10-50 mmol / L, and the buffer capacity can be achieved when the culture medium contains 20 mmol / L HEPES. Moreover, this kind of buffer has many advantages over phosphate buffer. It is non-toxic to cells and can control the constant pH range for a long time. It is a good hydrogen ion buffer.
hepes powder
The dissociation constant of HEPES buffer is 7.65 (at 20 ℃), and the pH buffer range is 6.6-8.6, which is generally suitable for the reaction system with pH 6.8-8.2. It can be used directly with sodium hydroxide, or mixed with salt and adjusted pH with sodium hydroxide.
1、 500 ml of 1 mol / L HEPES, pH 7.0, stock solution: weigh 0.5 mol (119.15 g) of hydroxyethyl piperazine ethanesulfonic acid, then adjust to the required pH value with 0.5 m ~ 1 M sodium hydroxide, finally fix the volume with distilled water, and seal at 4 ℃.
2、 HEPES buffer 500ml with a small amount of salt: HEPES ＞ 6.5g, NaCl ＞ 8.0g, na2hpo4.7h2o ＞ 0.198g, adjust pH value with 0.5m NaOH ＞ water solution, finally fix volume and store at low temperature.
3、 Preparation of 2 × HEPES buffer salt solution: 1.6g NaCl, 0.074g KCl, 0.027g na2hpo4.2h2o, 0.2g glucan or dextran and 1g HEPES were dissolved in 90ml distilled water, adjusted to the required pH value with 0.5m NaOH, and then diluted to 100ml with distilled water.
Although the buffer system of HEPES is not as extensive as that of PBS, it has more advantages. The ionic strength of PBS is higher than that of HEPES, and the ionic strength will affect the solubility of other solutes in the mixed solution. In general, where PBS can be used, HEPES can be used, but where HEPES is used, PBS cannot be replaced.
HEPES buffer is similar to pipe, but the water solubility of pipe is poor, so it can be made into sodium salt of pipe. The two buffers provided by Desheng are powder reagents, which can also be prepared into ready-to-use buffer solutions with specific concentrations if required.
