Hello Fan Janice

MOMIPP precipitates when diluted with PBS or culture media because it is a hydrophobic, water-insoluble compound that is typically dissolved in an organic solvent like DMSO for storage. When this stock solution is added to an aqueous, salt-rich medium like PBS or cell culture media, MOMIPP's low solubility causes it to come out of the solution and form a precipitate. You should prepare MOMIPP stocks at very high concentrations (such as 50mM) in DMSO to allow for small, precise additions to cell cultures. However, if the final concentration of MOMIPP exceeds its solubility limit in the aqueous media, precipitation is inevitable.

To dissolve MOMIPP for cell culture, you may use the "solvent shift" method by first dissolving a concentrated amount of MOMIPP in a small volume of DMSO, then diluting this stock into your cell culture medium to achieve the desired final concentration. This technique is effective for poorly soluble compounds like MOMIPP, enabling the creation of a supersaturated solution that resists precipitation and can be directly used in cell-based assays.

You may follow the below protocol.

1. Add an appropriate volume of high-purity DMSO to achieve a very concentrated stock solution (50mM).

2. Vortex until the MOMIPP is completely dissolved. If it doesn't dissolve immediately, you can briefly warm the solution to 37°C.

3. Before treating the cells, perform an initial dilution by adding the MOMIPP/DMSO solution dropwise into a portion of warm cell culture medium or warm FBS while gently mixing. Mixing during addition is critical to prevent sudden precipitation.

4. To aid in dispersing the compound, some protocols suggest a preliminary dilution into warm FBS (at 50°C) before adding it to the final medium.

5. Add this intermediate dilution to the full volume of pre-warmed cell culture medium needed for your experiment.

6. Finalize the concentration of MOMIPP and ensure the final concentration of DMSO in the cell culture medium is very low (typically less than 0.1%) to avoid solvent-induced cellular toxicity.

Please note that adding the concentrated DMSO stock dropwise to a large, warm volume of culture medium while mixing is the key to the "solvent shift" working effectively. Adding the stock too quickly or to a cold culture medium can cause the MOMIPP to precipitate out of solution.

Best,