title: Devising Self-Assembled-Monolayers for Surface-Enhanced Infrared Spectroscopy of pH-Driven Poly-l-lysine Conformational Changes.
abstract: Surface-enhanced infrared absorption spectroscopy (SEIRA) is applied to study protein conformational changes. In general, the appropriate functionalization of metal surfaces with biomolecules remains a challenge if the conformation and activity of the biomolecule shall be preserved. Here we present a SEIRA study to monitor pH-induced conformational changes of poly-l-lysine (PLL) covalently bound to a thin gold layer via self-assembled monolayers (SAMs). We demonstrate that the composition of the SAM is crucial. A SAM of 11-mercaptoundecanonic acid (MUA) can link PLL to the gold layer, but pH-driven conformational transitions were hindered compared to poly-l-lysine in solution. To address this problem, we devised a variety of SAMs, i.e., mixed SAMs of MUA with either octanethiol (OT) or 11-mercapto-1-undecanol (MUoL) and furthermore SAMs of MT(PEG)4 and NHS-PEG10k-SH. These mixed SAMs modify the surface properties by changing the polarity and the morphology of the surface present to nearby PLL molecules. Our experiments reveal that mixed SAMs of MUA-MUoL and SAMs of NHS-PEG10k-SH-MT(PEG)4 are suitable to monitor pH-driven conformational changes of immobilized PLL. These SAMs might be applicable for chemoselective protein immobilization in general.
authors.affiliation: Department of Chemistry, University of Konstanz , 78457 Konstanz, Germany.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Fallah
authors.affiliation: Max Planck Institute for Intelligent Systems , Department of New Materials and Biosystems, 70569 Stuttgart, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Stanglmair
authors.affiliation: Max Planck Institute for Intelligent Systems , Department of New Materials and Biosystems, 70569 Stuttgart, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Pacholski
authors.affiliation: Department of Chemistry, University of Konstanz , 78457 Konstanz, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Hauser
mesh_terms: D005233:Fatty Alcohols / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D011092:Polyethylene Glycols / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: C521238:11-mercaptoundecanol; D005233:Fatty Alcohols; D008567:Membranes, Artificial; D013438:Sulfhydryl Compounds; D011107:Polylysine; D011092:Polyethylene Glycols