title: Controlling orientations of immobilized oligopeptides using N-terminal cysteine labels.
abstract: This letter reports a strategy of using N-terminal cysteine labels for controlling the immobilization of oligopeptides on aldehyde-terminated surfaces through the formation of stable thiazolidine rings. We also study the effect of cysteine position (either N-terminal or C-terminal) and lysine residue on the immobilization of oligopeptides. On the basis of our ellipsometry and quartz crystal microbalance (QCM) results, we conclude that the proposed immobilization strategy is highly site-specific. It works only when cysteine is in the N-terminal position, and the formation of thiazolidine is much faster than the formation of imines between lysine residues and aldehydes, even in the presence of a reducing agent such as NaBH(3)CN. By labeling an oligopeptide CSNKTRIDEANNKATKML with an N-terminal cysteine, we immobilize this oligopeptide on an aldehyde-terminated surface and investigate the enzymatic activity of trypsin acting on the oligopeptide. It is found that trypsin is able to cleave the immobilized oligopeptide having a single anchoring point at the N-terminal cysteine. No cleavage is observed when the oligopeptide is immobilized through multiple anchoring points at lysine residues.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576.
authors.forename: Xinyan
authors.initials: X
authors.lastname: Bi
authors.forename: Deny
authors.initials: D
authors.lastname: Hartono
authors.forename: Kun-Lin
authors.initials: KL
authors.lastname: Yang
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D001671:Biochemistry / Q000379:methods; D003460:Crystallization; D003545:Cysteine / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D008239:Lysine / Q000737:chemistry; D008956:Models, Chemical; D009842:Oligopeptides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D053778:Thiazolidines / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry
chemical_list: D000447:Aldehydes; D009842:Oligopeptides; D010455:Peptides; D053778:Thiazolidines; D014357:Trypsin; D008239:Lysine; D003545:Cysteine