It's a lyophilized protein, buffered from a 0.2 um filtered solution of 20mM PB, 150mM NaCl, at pH 7.4. It's advised not to reconstitute it to a concentration below 100UG/ml. Dissolve the lyophilized protein in ddH2O. Its purity is over 95%, as confirmed by reducing SDS-PAGE, and the endotoxin level is less than 0.1 ng/ug (1 IEU/ug), as determined by the LAL test.