Nanoscopy

A first vibrational mapping on the nanometer scale was performed on a protein (streptavidin) labelled supported phospholipid film by means of tip-enhanced Raman spectroscopy (TERS). For this purpose a TERS spectral map was measured on the biomembrane model, using a step size far below the diffraction limit. Considering the model composition, spectra were classified as either typical for lipids, proteins or both simultaneously, in a qualitative manner. Subsequently, the spectroscopic information was assigned with respect to the topographic features. Since a spatial differentiation between different compositional domains is difficult to achieve by topographic features only, the combination of morphology and spectral data enables a much more detailed characterization of biomembranes. Schematic tip-sample interaction during TERS measurement on a membrane-based model system. Spectra occurring are representative of different biochemical domains, hence, TERS spectra are gained describing lipids and/or proteins. Several marker bands, highlighted by blue circle (lipid contribution) or red star (protein contribution) are used for specific assignment.