https://pages.htgaa.org/2026b/caleb-seward/week-03-hw-cfps/index.htmlA. Comparing compositions Potassium vs magnesium glutamate Magnesium glutamate is more sensitive. Potassium glutamate just sets the ionic background, approximating the cytoplasm the ribosome evolved in. The optimum is broad, so published values scatter from 130 mM in PANOx-SP to 362 mM in Olsen’s RFopt. Magnesium is a catalytic cofactor with a narrow window: free Mg2+ drives 30S/50S association, holds tRNA tertiary structure together, and is the catalytic metal for T7 polymerase and the synthetases. Too little and ribosomes don’t assemble, too much and elongation slows and fidelity drops. Across those same formulations it barely moves, 7 to 10 mM everywhere.Hugoen