Surface-enhanced Raman scattering (SERS) spectra of sialic acid (SA) benzyl, and methyl glycosides as well as natural sialylated glycoproteins from human cells of healthy donors and tumor patients have been analyzed in view of the fact that peripheral fragments of many bioactive glycoconjugates are SA residues. SA residues can be detected by SERS at concentrations as low as 10−6 M. The pattern of interaction of SA with the surface of a silver hydrosol involves the C-8 and C-9 hydroxy groups of SA. SERS spectroscopy is sensitive to changes in the content and type of branching of sialylated sugar chains in sialylglycoproteins. The differences in sialylated sugar-chain organization for α1-acid glycoproteins from healthy donors and tumor patients have been detected by means of SERS spectroscopy. The first example of the detection of SA residues for a suspension of living cells has been presented.
Konstantin V. Sokolov, Nargiz E. Byramova, Larisa V. Mochalova, Alexander B. Tuzikov, Svetlana D. Shiyan, Nicolai V. Bovin, and Igor R. Nabiev, "Detection of Sialic Acid Residues and Studies of Their Organization in Normal and Tumor α1-Acid Glycoproteins as Probed by Surface-Enhanced Raman Spectroscopy," Appl. Spectrosc. 47, 535-538 (1993)