N,N'-DI-L-LYSYL-L-CYSTINE DIHYDROCHLORIDE, with the CAS number 2920735-07-3, is a high-performance peptide derivative, also known as CQ rex® KC. Its molecular formula is C₁₈H₃₈Cl₂N₆O₄S₂, and its molecular weight is approximately 517.48 g/mol. Composed of two L-lysine molecules and one L-cystine molecule linked by peptide bonds, with two hydrochloride groups, it is specifically designed to overcome the low solubility limitation of free L-cystine, featuring excellent stability and biocompatibility, widely applied in bioprocessing, biochemistry, and pharmaceutical fields.
Physically, it appears as a white to off-white crystalline powder. It has a high solubility in water—about 1000 times more soluble than free L-cystine at neutral pH—and is slightly soluble in methanol and ethanol, insoluble in non-polar solvents. It is optically active and stable under normal temperature and pressure, with low hygroscopicity, making it easy to handle and suitable for formulating concentrated cell culture media without precipitation issues.
Chemically, its hydrochloride form enhances solubility and stability, while the peptide bond structure ensures it remains stable in aqueous and physiological environments. It can be hydrolyzed under appropriate conditions to release L-lysine and L-cystine, both essential for protein synthesis and intracellular redox balance. Unlike free L-cysteine, it avoids rapid oxidation and reduces reactive oxygen species (ROS) formation, minimizing cytotoxicity even at high concentrations.
Its core application lies in bioprocessing and cell culture, where it serves as a high-efficiency cystine source in chemically defined media. It enables the preparation of highly concentrated feeds, simplifies bioprocesses, and improves cell viability and antibody titer in CHO cells and other cell lines used for monoclonal antibody production. It also acts as a biochemical reagent for studying redox homeostasis and peptide metabolism, and as an intermediate in pharmaceutical synthesis.
Safety-wise, it is a mild irritant; contact with skin, eyes, or respiratory tract should be avoided. Proper protective equipment is recommended during handling. It should be stored in a sealed, cool, dry, and dark environment at 10-25℃, away from oxidants and moisture, to maintain its stability and purity. With its superior solubility and performance, it is an indispensable raw material for advanced bioprocessing and life science research.
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