Protein-membrane interaction plays an important role in various crucial biological processes. We present a novel lipid-cushioned nanoporous silver sheet for the sensitive SERS structural characterization of membrane proteins in tunable lipid environments by combination with surface-enhanced Raman spectroscopy and Langmuir technique. We investigate different membrane proteins on this substrate under different lipid environments. Our results indicate that melittin penetrates the membrane hydrophobic region in helical structures. Interesting, the hydrophobic effect drives the formation of β-sheet alpha-synuclein from the disordered state in aqueous solution, which might provide new insights to understand its membrane toxicity and the pathogenic mechanism of Parkinson’s disease. Moreover, l...[ Read more ]

Protein-membrane interaction plays an important role in various crucial biological processes. We present a novel lipid-cushioned nanoporous silver sheet for the sensitive SERS structural characterization of membrane proteins in tunable lipid environments by combination with surface-enhanced Raman spectroscopy and Langmuir technique. We investigate different membrane proteins on this substrate under different lipid environments. Our results indicate that melittin penetrates the membrane hydrophobic region in helical structures. Interesting, the hydrophobic effect drives the formation of β-sheet alpha-synuclein from the disordered state in aqueous solution, which might provide new insights to understand its membrane toxicity and the pathogenic mechanism of Parkinson’s disease. Moreover, lower packing density of lipid coatings result in stronger SERS signals from phenylalanine residues, which might provide more structural details to support the barrel model in membrane toxic mechanism formed by alpha-synuclein pores. Furthermore, stress tolerance mechanism of tardigrade intrinsically disordered protein (HeLEA) is recently proposed through direct membrane interaction and may affect the physical properties of membranes. Revealed by circular dichroism titration and structural characterization on our SERS platform, HeLEA undergoes a disordered-to-α-helix structural transition during membrane binding. Meanwhile, the characterization via Langmuir methodologies indicates that HeLEA increases the membrane fluidity through electrostatic interaction with negatively charged lipids, which might provide biophysical details on illustrating its mechanism of stress tolerance. With the great biomimicking capability and tunability, it is believed that our novel SERS approach simplifies complicated natural membrane environments and offers a convenient platform to investigate protein structural changes in protein-membrane interactions under specific membrane-associated factors.