Supplements & Reagents FAQs

Both freezing media are formulated for use on typical cell lines found in the laboratory. For some cell lines, the higher concentration of fetal bovine serum in Cell Freezing Medium II provides more cryoprotection and better yields of viable cells upon thawing. More hardy cell lines can be cryopreserved adequately in Cell Freezing Medium I at a lower cost. The choice should be made based on past experience with the specific cell line.

HEPES (N-2-hydroxyethylpiperazine-N’-2-ethanesulfonic acid, pKa@37°C=7.3, useful range pH 6.6 – 8.0) is one of several biological buffers that can be used to stabilize the pH of cell culture medium. As cells grow and metabolize the cell culture medium nutrients, they typically produce excess acid – that lowers the pH of the medium. This lowering of pH can be detrimental to the continued growth of cells in culture. HEPES provides more “buffering” capacity than the bicarbonate normally found in cell culture medium – thus slowing the decline in pH as cells metabolize the nutrient medium. For some cell lines this extends the time between “feedings” and promotes healthier cell growth. HEPES can show toxicity with some cell lines, so it is not a universal panacea. Other useful biological buffers include MOPS (pKa@37°C=7.0), TRIS (pKa@37°C=7.8), and PIPES (pKa@37°C=6.7).

L-glutamine is an essential amino acid and plays a major role for the growth and function of cells in culture. Although L-glutamine is stable in crystalline form, it has the tendency to degrade non-enzymatically and irreversibly in solution within a short time period. The rate of this L-glutamine breakdown is dependent on pH, temperature and the presence of various anions

One of the by-products, ammonia, may act as a toxin or growth inhibitor for the cultured cells.

Because of its chemical instability and significance for cell growth, it is important that the delivery of L-glutamine be optimized to each specific cell culture application.

A recommended way of achieving reliable delivery of L-glutamine to the cells in culture is the use of stable derivatives of L-glutamine in cell culture media.

Atlanta Biologicals brand GlutaminePlus, a derivative of L-glutamine obtained by a chemical reaction of L-alanine with L-glutamine, is available in liquid form or as an ingredient in ready-to-use Atlanta Biologicals brand cell culture media (media with stable L-glutamine).

GlutaminePlus is metabolized within the cells to yield L-glutamine plus the second amino acid. This results in more consistent delivery of L-glutamine to cells in culture and avoids toxic buildup of ammonia in cell cultures. This feature can be especially important for ammonia sensitive cell lines.