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Abstract

The in situ control of reversible protein adsorption to a surface is a critical step towards biofouling prevention and finds utilisation in bioanalytical applications. In this work,} adsorption of peptides is controlled by employing the electrode potential induced{,} reversible change of germanium (100) surface termination between a hydrophobic{,} hydrogen terminated and a hydrophilic{,} hydroxyl terminated surface. This simple but effective {'}smart{'} interface is used to direct adsorption of two peptides models{,} representing the naturally highly abundant structural motifs of amphipathic helices and coiled-coils. Their structural similarity coincides with their opposite overall charge and hence allows the examination of the influence of charge and hydrophobicity on adsorption. Polarized attenuated total reflection infrared (ATR-IR) spectroscopy at controlled electrode potential has been used to follow the adsorption process at physiological \pH\ in deuterated buffer. The delicate balance of hydrophobic and electrostatic peptide/surface interactions leads to two different processes upon switching that are both observed in situ: reversible adsorption and reversible reorientation. Negatively charged peptide adsorption can be fully controlled by switching to the hydrophobic interface{,} while the same switch causes the positively charged helical peptide to tilt down. This principle can be used for {'}smart{'} adsorption control of a wider variety of proteins and peptides and hence find application{, e.g. as a bioanalytical tool or functional biosensors.