Application of hydroxyethylpiperazine ethanesulfonic acid (HEPES) in biology
Hydroxyethylpiperazine ethanesulfonic acid (HEPES) is a widely used buffer with strong buffering capacity (pH 6.8 ~ 8.2), and it is not affected by external factors and does not form a buffer-metal ion complex. It is widely used in physiological, biochemical and pharmacological research. In fact, it is not limited to these applications, it also has its traces in our biology.
Block anion channel
HEPES is a commonly used perfusate pH stabilizer. Perfusate containing 155mmol/L HEPES (abbreviated as HBM) can block the depolarizing current of cochlear neurons permeabilized by acetylcholine. 10mmol/L HEPES HBM can produce a voltage-dependent blocking effect on the Cl- channel of Drosophila neurons, which is manifested as a decrease in channel current. When the inner surface of the cell membrane is exposed to HBM, the blocking effect is particularly significant, and this effect can be cancelled after washing with perfusate without buffer. The blocking effect of HEPES on the outward rectifying anion channel. Whether it is the inside or outside of the cell membrane, HEPES has a blocking effect on this channel.
Affect the growth of cultured cells
When endothelial cells are cultured in HEPES medium, cell growth is inhibited, endothelial cells can produce O2-, and HEPES promotes the increase of O2- production. Excessive O2- causes an increase in toxic products such as H2O2, OH- and other substances in endothelial cells, which inhibits and poisons the growth of endothelial cells. HEPES can also cause abnormal RNA transcription in cultured cells.
Inhibit smooth muscle strength
Compared with BBM at 5.0mmol/L HBM, the contractility of rat aortic strips in HBM induced by norepinephrine (NE) was significantly lower than that of the control group in BBM, and the frequency of spontaneous contraction of blood vessel strips was correspondingly slower. , Replacing HBM with BBM can completely cancel this effect. Using a variety of receptor blockers can not remove the inhibitory effect of HEPES, indicating that this inhibition may not be mediated by the receptor. A similar effect was observed in the rat vas deferens.
Affect blood clotting time
Clinically, HEPES is sometimes used as a stabilizer for plasma samples in coagulation experiments. Studies have found that HEPES can shorten prothrombin time and fibrin polymerization time (FMP) to the extent that it masks abnormal results. For some liver diseases (with hypofibrinemia) and some acquired hypofibrinemia, HEPES conceals the abnormality of FMP, thereby correcting the prolonged clotting time, which makes the correct diagnosis impossible.
Other effects of HEPES
In the experiment of the effect of Ach on the firing rate of neuronal impulse of frog semicircular canal with HEPES as a buffer, Ach can have a two-way effect on the firing rate of neuronal impulse in BBM, while in HBM, Ach only produces inhibition. This effect is consistent with the effect of adding atropine. The author believes that HEPES is a derivative of piperazine, piperazine has anticholinergic effect, so HEPES may have M receptor antagonism.
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