The BLUelf Prestained Protein Ladder is a three-color protein standard with 13 prestained proteins covering a wide range molecular weights from 3.5 to 245 kilodalton (kDa). Proteins are covalently coupled with a blue chromophore except for two reference bands (one green and one red band at 25 kDa and 75 kDa respectively) when separated on SDS-polyacrylamide gel electrophoresis (SDSPAGE) with Tris-glycine-SDS running buffer. The BLUelf Prestained Protein Ladder is designed for monitoring protein separation during SDS-PAGE, verification of Western transfer efficiency on membranes (PVDF, nylon, or nitrocellulose) and for approximating the size of p roteins. The ladder is supplied in gel loading buffer and is ready to use. Do not heats, dilute, and add reducing agent before loading.