Description_x000D_ General description_x000D_ SILu™Prot SOST is a recombinant, stable isotope-labeled human SOST which incorporates [13C6, 15N4]-Arginine and [13C6, 15N2]-Lysine. Expressed in human 293 cells, it is designed to be used as an internal standard for bioanalysis of SOST in mass-spectrometry. SILu™Prot SOST is a protein of 201 amino acids (including a N-terminal polyhistidine and tag), with a calculated molecular mass of 22.8 kDa._x000D_ Biochem/physiol Actions_x000D_ Sclerostin is a secreted Wnt signaling antagonist produced almost exclusively by osteocytes. It can selectively inhibit Wnt/ β-catenin, suppressing the activity of osteoblasts as well as the viability of osteoblasts and osteocytes. Lower sclerostin levels are associated with lower bone mineral content and bone. It was demonstrated that greater total limb bone mineral content was significantly associated with greater circulating levels of sclerostin. In addition, circulating sclerostin is a biomarker of osteoporosis severity in long-term, chronic paraplegia. Serum sclerostin was associated significantly, independently, and positively with bone mineral density of both cortical and cancellous bone. Sclerostin is considered to be one of the factors associated with chronic kidney disease-mineral and bone disorder in hemodialysis patients._x000D_ Sequence_x000D_ HHHHHHHHGGQQGWQAFKNDATEIIPELGEYPEPPPELENNKTMNRAENGGRPPHHPFETKDVSEYSCRELHFTRYVTDGPCRSAKPVTELVCSGQCGPARLLPNAIGRGKWWRPSGPDFRCIPDRYRAQRVQLLCPGGEAPRARKVRLVASCKCKRLTRFHNQSELKDFGTEAARPQKGRKPRPRARSAKANQAELENAY_x000D_ Physical form_x000D_ Supplied as a lyophilized powder containing phosphate buffered saline._x000D_ Legal Information_x000D_ SILu is a trademark of Sigma-Aldrich Co. LLC