Endotoxins: What They Are, Why They Matter, and How to Read the Test
Bacterial endotoxins are one of the most overlooked contaminants in research peptides. Learn what endotoxins are, why they matter, and how to interpret your endotoxin report.
May 20, 2026 | 6 min read
What Are Endotoxins?
Endotoxins are lipopolysaccharides (LPS) — fragments of the outer membrane of gram-negative bacteria. They are released when bacteria die and their cell walls break apart. In peptide synthesis, bacterial contamination can occur at any stage of the manufacturing process, and even dead bacteria leave behind endotoxin fragments.
Endotoxins are extraordinarily potent biological agents. At concentrations as low as 1 nanogram per kilogram of body weight, they can trigger fever, inflammation, and in severe cases, septic shock. For in vivo research, even trace endotoxin contamination can completely invalidate experimental results by triggering immune responses that have nothing to do with the compound being studied.