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Scientific FAQs

Jul 28,2014 08:07  |  Resource

FAQs


Question 1: How stable is a compound in typical cell culture media?  For cell culture, do I need to change media every day?

Answer: Chemical compounds are typically stable in cell culture media for at least a couple of days. In most scenarios, compounds are freshly added to the media each time when you re-constitute or change the culture condition (e.g., in every medium change). In some cases, you can store the compound and other supplements constituted media in cold room for longer period of time (e.g., 1-2 weeks) for more convenient routine medium change. Normally you do not need to change media every day unless it is specially noted in the original publication or you notice a clear decrease of its effect after one day. All of our provided chemical compounds were used in published studies, which should serve as your references in designing your experiments.

 

Question 2: Are compounds sensitive to freeze-thaw cycle?

Answer:  Unlike proteins (e.g., growth factors or peptides), most of small molecule compounds are not sensitive to freeze-thaw cycle. Their stock solution (e.g., in DMSO) can be frozen and thawed multiple times. However, we suggest you aliquot your 10 mM DMSO stock solution into 50 ul aliquots if you freeze them. Occasionally, certain chemical compounds may precipitate out in low temperature, and they need to be fully re-dissolved upon warming up (tapping or gentle vortexing the tube or vial).   

 

Question 3: Is a compound soluble in another solvent other than DMSO?

Answer: You will need to email us about your specific compound’s solubility question: info@xcessbio.com. Different compound has different solubility characteristics. Generally the most commonly used solvent for dissolving a chemical compound is DMSO, which is suitable for most applications. For making DMSO stock solution, we suggest you to make a 10 mM or higher concentration of a compound, thus typically a more than 1000X dilution would be applied when making the final concentration of the compound in cell culture media to minimize any solvent effect on your cells (typically less than 0.5% of DMSO might be tolerable by most of cell types).

 

In some cases, you may consider dissolving compounds in ethanol, which however is a lot more volatile and may not work well with precise pipetting of low volume.  Most compounds would not be soluble in solely water-based solution (e.g., PBS or cell culture media) at high concentrations (e.g., over 50 uM).

 

Question 4: If I want to make a stock of DMSO solution of a compound, what is the stock concentration of a compound you’d suggest to use?

 Answer: 10 mM or higher.

 

Question 5: Can I make intermediate dilutions of a compound in water-based solution and store them for regular use?

Answer: No, in most cases. Most compounds would not be soluble in solely water-based solution (e.g., PBS or cell culture media) at high concentrations (e.g., over 50 uM). We suggest you directly dilute your compound’s DMSO stock solution into final concentration in the cell culture media.

 

Question 6: What should I do if I ordered a DMSO solution of a compound and see precipitation?

Answer: Due to temperature and pressure changes during shipping, especially on international flight, certain compounds may precipitate from the DMSO solution. For international orders, we suggest you order solid form of a compound. If you see compound precipitation upon receiving, please try to fully re-dissolve it upon warming up and tapping or gently vortexing the tube or vial.   

 

To keep the right concentration in a solution, please do not filter the precipitated compound out. Certain compounds will precipitate after freeze-thaw cycle. We will notify you about those compounds specifically upon shipping them. For those compounds, leave the solutions at room temperature and do not freeze them.

 

Question 7: What should I do if have ordered the solid form of a compound for my in vitro assay?

Answer: Typically if you do not intend to use all of the compound at once, you’d dissolve it in an appropriate solvent (e.g., DMSO or read relevant Q&A above) to make 10 mM or higher stock concentration of the compound for your regular use. 

 

Question 8: What is the highest DMSO concentration to use in cell culture?

Answer: Typically <0.5-1% DMSO is tolerable by many cancer cells in culture. For more sensitive cells such as primary cells, try to use <0.1% DMSO in the cell culture.