title: Affibody protein capture microarrays: synthesis and evaluation of random and directed immobilization of affibody molecules.
abstract: Affibody molecules, 58-amino acid three-helix bundle proteins directed to different targets by combinatorial engineering of staphylococcal protein A, were used as capture ligands on protein microarrays. An evaluation of slide types and immobilization strategies was performed to find suitable conditions for microarray production. Two affibody molecules, Z(Taq) and Z(IgA), binding Taq DNA polymerase and human IgA, respectively, were synthesized by solid phase peptide synthesis using an orthogonal protection scheme, allowing incorporation of selective immobilization handles. The resulting affibody variants were used for random surface immobilization (through amino groups) or oriented surface immobilization (through cysteine or biotin coupled to the side chain of Lys58). Evaluation of the immobilization techniques was carried out using both a real-time surface plasmon resonance biosensor system and a microarray system using fluorescent detection of Cy3-labeled target protein. The results from the biosensor analyses showed that directed immobilization strategies significantly improved the specific binding activity of affibody molecules. However, in the microarray system, random immobilization onto carboxymethyl dextran slides and oriented immobilization onto thiol dextran slides resulted in equally good signal intensities, whereas biotin-mediated immobilization onto streptavidin-coated slides produced slides with lower signal intensities and higher background staining. For the best slides, the limit of detection was 3 pM for IgA and 30 pM for Taq DNA polymerase.
authors.affiliation: Department of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Renberg
authors.forename: Ikue
authors.initials: I
authors.lastname: Shiroyama
authors.forename: Torun
authors.initials: T
authors.lastname: Engfeldt
authors.forename: Per-Ke
authors.initials: PK
authors.lastname: Nygren
authors.forename: Amelie Eriksson
authors.initials: AE
authors.lastname: Karlström
mesh_terms: D000345:Affinity Labels / Q000138:chemical synthesis / Q000737:chemistry; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry; D008024:Ligands; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D040081:Protein Array Analysis / Q000295:instrumentation / Q000379:methods*; D040901:Proteomics / Q000295:instrumentation / Q000379:methods*; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D013205:Staphylococcal Protein A / Q000737:chemistry; D019809:Streptavidin / Q000737:chemistry; D020349:Surface Plasmon Resonance; D019914:Taq Polymerase / Q000737:chemistry
chemical_list: D000345:Affinity Labels; D007070:Immunoglobulin A; D008024:Ligands; D010455:Peptides; D011993:Recombinant Fusion Proteins; D013205:Staphylococcal Protein A; C504345:affibody Z(IgA); C504343:affibody Z(Taq); D019809:Streptavidin; D019914:Taq Polymerase