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What are the differences between HEPES (7365-45-9) and Tris (77-86-1) buffer?

2017-08-23 来源:亚科官网
23 August 2017
  In the biochemical experiment, the buffer solution plays an indispensable role, it can resist the effect of a small amount of strong acid and alkali, and maintain the pH value the most close to the physiological environment for the system. HEPES buffer and Tris buffer are commonly used in biological experiments buffer, and many people often have doubts: What is the difference between the two? This article will be a comparative summary.
Introduction and Application
  HEPES is a zwitterionic bio-buffer, belonging to the Good's buffer, the effective buffering range is 6.8 to 8.2, and can be widely used as a buffer reagent in a variety of biochemical reactions, and some cells culture medium. The final concentration of HEPES is 10~50mmol/L, the general culture medium containing 20mmol/L can achieve the buffer ability. In addition, HEPES buffers are commonly used in organelles and proteins and enzymes with mutability and pH-sensitivity, as well as biochemical diagnostic kits, DNA/RNA extraction kits and PCR diagnostic kits.
  Tris buffer: Tris is weakly alkaline, pKa is 8.1 at 25°C, and the effective buffering range is 7.0~9.2, the commonly used pH in biochemical experiments was 6.8, 7.4, 8.0, 8.8. It is often used as a buffer in the electrophoresis and gel experiments, or as nucleic acid and protein solvents, even the formation of nematodes intermediate fibers. Its derived buffers TE, TAE, TBE, etc. are commonly used in DNA stability, storage and extraction.
Characteristics of the two buffers
  HEPES buffers, and even all Good's buffers have the following characteristics:
PKa values are between 6.0 and 8.0;
high solubility in water;
With membrane impermeability, not easy to penetrate the biofilm;
The impact to biochemical reaction is limited, can be resistant to chemical action and enzymatic hydrolysis, and does not produce complexes or precipitation with metal ions;
Very low visible light and ultraviolet light absorption;
Ion concentration, solution composition and temperature have little effect on dissociation;
  Tris buffer solution has the following characteristics:
Alkaline, only Tris-HCl buffer system can be prepared pH range from acidic to alkaline buffer, and can be composed with other substances to form a variety of buffer systems, such as TE, TBS, TAE, TBE and other derivative buffer;
Interference with the biochemical process is very small, no precipitation with calcium, magnesium ions and heavy metal ions;
Affected by the solution concentration, dilution ten times, pH change greater than 0.1;
Affected by the environment, in general, when the temperature increases 1°C, the pH decreased 0.03; easy to absorb CO2.
Buffer preparation method
  The preparation of HEPES buffer solution, depending on the application, one is pure HEPES + NaOH and the other is HEPES + salt:
First, HEPES + NaOH (500 mL)
119.15g HEPES is dissolved in 400mL distilled water, add 0.5~1M NaOH aqueous solution to adjust the pH, and then make it 500mL with distilled water.
Second, HEPES + salt (500mL)
HEPES 6.5g, NaCl 8.0g, Na2HPO4·7H2O 0.198g, adjusted the pH with 0.5M NaOH aqueous solution and make it 500mL.
  There are two methods for the preparation of Tris-HCl buffer:
First, 0.05mol/L Tris and 0.05mol/L HCl solution were prepared and then mixed according to the volume listed in the usual table. As the standard concentration of dilute hydrochloric acid is not easy to prepare, so we commonly used the second method.
In the case of 1L 0.1mol/L Tris-HCl buffer: 12.11g of Tris base was dissolved in 950~970mL deionized water, and 4N HCl was added dropwise with stirring to determine the pH of the solution, and then add water to make it 1L.
  In summary, HEPES and Tris buffer have differences in the buffering range, application areas, as well as the characteristics and methods of preparation. In the specific experiment, the experimental conditions should be analyzed carefully. In addition, it should be noted that in the ion exchange chromatography, if the cation exchange column was used, Tris buffer should be avoided because of carrying positive charge, while HEPES belongs to zwitterionic buffer, caution and anion ion exchange chromatography are both applicable.
Related Links: Tris
Edited by Suzhou Yacoo Science Co., Ltd.