Nanoplasmonic Sensor Detects Preferential Binding of IRSp53 to Negative Membrane Curvature.

Gustav Emilsson,John Manzi,Bita Malekian,Feng-Ching Tsai,Evelyn Röder,Kunli Xiong,Marta Bally,Nam-Joon Cho,Andreas Dahlin

doi:10.3389/fchem.2019.00001

Abstract

Biosensors based on plasmonic nanostructures are widely used in various applications and benefit from numerous operational advantages. One type of application where nanostructured sensors provide unique value in comparison with, for instance, conventional surface plasmon resonance, is investigations of the influence of nanoscale geometry on biomolecular binding events. In this study, we show that plasmonic “nanowells” conformally coated with a continuous lipid bilayer can be used to detect the preferential binding of the insulin receptor tyrosine kinase substrate protein (IRSp53) I-BAR domain to regions of negative surface curvature, i.e., the interior of the nanowells. Two different sensor architectures with and without an additional niobium oxide layer are compared for this purpose. In both cases, curvature preferential binding of IRSp53 (at around 0.025 nm−1 and higher) can be detected qualitatively. The high refractive index niobium oxide influences the near field distribution and makes the signature for bilayer formation less clear, but the contrast for accumulation at regions of negative curvature is slightly higher. This work shows the first example of analyzing preferential binding of an average-sized and biologically important protein to negative membrane curvature in a label-free manner and in real-time, illustrating a unique application for nanoplasmonic sensors.

Highlights

Biosensors based on plasmonic nanostructures have been a subject of intense research for 20 years (Jackman et al, 2017; Lopez et al, 2017; Zhang et al, 2017)
We have suggested that one unique type of application for plasmonic nanostructures is to study the effects of lipid membrane curvature on biomolecular interactions (Junesch et al, 2015; Ferhan et al, 2018)
Using plasmonic nanowells (Junesch et al, 2012; Malekian et al, 2017), we have shown that proper spectral analysis can detect whether binding occurs preferentially to negative curvature, i.e., at the membrane invaginations formed inside the nanowells (Junesch et al, 2015; Ferhan et al, 2018)

Summary

Introduction

Biosensors based on plasmonic nanostructures have been a subject of intense research for 20 years (Jackman et al, 2017; Lopez et al, 2017; Zhang et al, 2017). In this work we evaluate the curvature-dependent interaction of the I-BAR domain of the IRSp53 protein with membranes containing negatively charged lipids (Mattila et al, 2007). These values are in fair agreement with the experimental peak and dip positions in Figure 2A (The experimental Nb2O5 nanowells were prepared with colloids that gave a shorter center to center distance of ∼230 nm compared to the simulated period of 300 nm, which explains the relatively large difference between simulation and experiment in that particular case).

Results

Conclusion