IGF-LR3 — 1 mg

Long R3 IGF-I is an engineered version of human insulin-like growth factor I. Sigma identifies two changes: replacement of the third-position glutamate with arginine and addition of a thirteen-amino-acid amino-terminal extension. Together, these produce the 83-residue molecule commonly sold as IGF-1 LR3. The supplier developed its recombinant material as a growth-factor supplement for low-serum or serum-free culture and documents biological activity through protein-synthesis responses in L6 myoblasts. These specifications provide a concrete molecular meaning for an otherwise abbreviated product name.

Umbrella Labs explicitly labels its related vial IGF-1 LR3 and describes diminished interactions with IGF-binding proteins and increased activity in cell culture. The company also describes the analogue as longer acting; that seller characterization should not be converted into a universal human half-life claim without a matching pharmacokinetic study. The core research application is manipulation of IGF signaling under controlled laboratory conditions. Native IGF-I, des(1–3)IGF-I, and IGF-II remain distinct comparison materials, and the requested abbreviation is best expanded to IGF-1 LR3 only where the underlying product specification confirms that identity.