Optical Materials (OM)
Devising self-assembled-monolayers for
Devising self-assembled-monolayers for surfaceenhanced infrared spectroscopy of pH-driven poly-L-lysine conformational changes
M. A. Fallah, C. Stanglmair, C. Pacholski, K. Hauser
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.
Journal Article