company news about Why should the prepared CAPS buffer solution be prevented from repeated freezing and thawing?

In experimental studies such as biochemistry and molecular biology, CAPS (3-cyclohexylamine-1-propanesulfonic acid) buffer solution is often used in experiments such as protein electrophoresis and enzyme activity determination due to its good buffering properties, providing a stable alkaline environment for biological molecules. However, in actual use, researchers often receive reminders to "avoid repeated freezing and thawing". Behind this requirement, the chemical properties of CAPS buffer solution, physical changes during freezing and thawing, and potential impact on experimental results are involved.

1. Characteristics and mechanism of action of CAPS buffer solution
CAPS is a commonly used biological buffer. Its molecular structure contains sulfonic acid and amine groups, which can maintain the relative stability of the solution pH in an alkaline environment through dissociation and protonation. When acidic or alkaline substances are added to the CAPS buffer solution, the CAPS molecules will bind or release protons accordingly, and adjust the hydrogen ion concentration in the solution through their own dissociation equilibrium, thereby controlling the pH value within a certain range.

2. Physical effects of repeated freezing and thawing on CAPS buffer solution
When CAPS buffer solution is frozen, the water in it will gradually crystallize to form ice crystals. The formation of ice crystals is not uniformly distributed, but grows preferentially at the edge of the solution and in areas where impurities exist. As the ice crystals continue to expand, the solutes in the solution will be squeezed into the unfrozen solution area, resulting in a local increase in the solute concentration. During the thawing process, the ice crystals melt and the solution volume is restored, but at this time the solute distribution inside the solution is no longer uniform. Repeated freezing and thawing causes this process to repeat continuously, and the solution volume frequently expands and contracts, destroying the uniformity of the solution.

3. Chemical effects of repeated freezing and thawing on CAPS buffer solution
(I) Decreased buffering performance
Repeated freezing and thawing may destroy the structure and stability of CAPS molecules. CAPS molecules play a buffering role in a specific conformation in the solution, and the temperature changes, solute concentration fluctuations and mechanical effects of ice crystals during the freezing and thawing process may cause degradation, polymerization or other chemical changes in CAPS molecules. These changes will change the dissociation characteristics of CAPS molecules, weakening or even losing their buffering capacity. When the buffering performance decreases, the CAPS buffer solution cannot effectively maintain pH stability when facing external acid-base changes, thus affecting the experimental results that rely on it to provide a stable environment.

(II) Chemical reaction with other components
Many CAPS buffer solutions will add other components when they are prepared to meet different experimental needs. Repeated freezing and thawing may promote chemical reactions between these components or between CAPS molecules. Some temperature-sensitive components may decompose during the freezing and thawing process, producing new impurities, which may interfere with the biological molecules in the experimental system and cause deviations in experimental results.

4 The impact of repeated freezing and thawing on experimental results
The use of CAPS buffer solutions that have been repeatedly frozen and thawed may lead to large errors in experimental results. For example, in protein research experiments, unstable pH environments can affect the charge and activity of proteins, making the separation, purification and identification of proteins inaccurate. In the long run, not only will experimental materials and time be wasted, but the direction of the experiment may also be misled.