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#DMEM

2 public questions tagged with this topic.

Animal Tissue Culture 1

DMEM generally requires CO₂ concentration of:

Nutrient dense formulation of Dulbecco's Modified Eagle's Medium doubles concentration of essential and nonessential amino acids compared to MEM original Eagle minimal essential medium, quadruples vitamin concentrations niacinamide B3, pyridoxal B6, riboflavin B2 to support nucleotide and cofactor synthesis in rapidly proliferating transformed cells, increases glucose from 1 to 4.5 grams per liter to sustain high glycolytic flux, includes sodium pyruvate 110 mg per liter as additional carbon source, designed for plaque assays viral growth and high density cultures where cell number reaches 10^6 per ml producing substantial lactate titrating buffer. Buffer requirement increased correspondingly to 3700 milligrams per liter sodium bicarbonate equivalent 44 mM versus MEM 1000 mg 13 mM and RPMI 2200 mg 26 mM. Henderson-Hasselbalch equation pH equals 6.1 plus log([HCO3-]/[CO2]) predicts maintaining pH 7.4 with elevated numerator demands proportional rise in denominator dissolved CO2 achieved by raising incubator CO2 to 7.5 to 10 percent rather than standard 5 percent. Culturing DMEM high bicarbonate at low CO2 results alkaline pH 8.

Ref: Dulbecco & Freeman Virology 1959 DMEM 3700 mg/L bicarbonate requires 10% CO2; ATCC media guide MEM RPMI DMEM comparison.

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Animal Tissue Culture 1

The pink to yellow color change in DMEM indicates:

Metabolic basis for color change reflects shift toward glycolytic phenotype characteristic of rapidly dividing cells in vitro despite ample oxygen availability phenomenon termed Warburg effect observed initially in tumors but also in normal proliferating cultures. Cells convert glucose to pyruvate via glycolysis then lactate via lactate dehydrogenase tetramer reducing NADH to NAD+ maintaining redox balance, exporting lactate plus proton via monocarboxylate transporter MCT4 SLC16A3 electrogenic process acidifying extracellular milieu even when mitochondrial oxidative phosphorylation functional. Simultaneously citric acid cycle produces carbon dioxide diffusing across lipid bilayer hydrating to carbonic acid via membrane associated carbonic anhydrase IX expressed under hypoxia inducible factor one alpha. Both lactic acid pKa 3.86 and carbonic acid donate protons to bicarbonate buffer consuming HCO3- converting to H2CO3 that dissociates to CO2 plus water removed in incubator exhaust. Accumulation of protons lowers medium pH from 7.4 toward 6.8 shifting phenol red equilibrium to protonated yellow form as absorbance at 560 drops and 430 rises perceived yellow.

Ref: Eagle 1973 lactate acidification Warburg glycolysis MCT4; Gibco Cell Culture phenol red yellow acid pink alkaline contamination cue.

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