CMAS Full-Length MS Protein Standard (NP_061156), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. Sialic acids are a family of nine-carbon sugars on cell surface glycoproteins and glycolipids that play a pivotal role in determining the structure and function of many animal tissues. The pattern of cell surface sialylation is highly regulated during embryonic development and N-glycosylation is a common post-translational modification during cellular differentiation. Sialic acids play important roles in cell-cell communications and immune responses. Sialylated glycoprotein and glycolipid formation requires the activation of a sialic acid to a cytidine monophosphate (CMP) diester by the enzyme encoded by this gene: CMP-N-acetylneuraminic acid synthetase.