How to operate the "repeated freeze-thaw" process mentioned in tissue or cell sample processing?

Tissue sample: After finishing tissue grinding, place it at -80℃ for 1h/ liquid nitrogen for 0.5h, and then gently shake it in a water bath at 30℃ to melt it quickly. Repeat this operation 1-2 times. Cell sample: Repeat the above freeze-thaw operation 2-3 times. If it is a membrane protein, it can be appropriately sonicated, but the temperature and frequency of ultrasound need to be controlled. It is recommended to add protease inhibitors to the sample in advance. PMSF(Cat.E-EL-SR002) is generally recommended.