| AVS 61st International Symposium & Exhibition | |
| Fundamentals & Biological, Energy and Environmental Applications of Quartz Crystal Microbalance Focus Topic | Thursday Sessions |
| Session QC+AS+BI+MN-ThA |
| Session: | Applications of QCM |
| Presenter: | Ralf Richter, CIC biomaGUNE & Université Grenoble Alpes & MPI Intelligent Systems, Spain |
| Authors: | N.B. Eisele, CIC biomaGUNE, Spain S. Ehret, CIC biomaGUNE, Spain R. Zahn, CIC biomaGUNE, Spain S. Frey, MPI Biophysical Chemistry, Germany D. Gorlich, MPI Biophysical Chemistry, Germany R.P. Richter, CIC biomaGUNE & Université Grenoble Alpes & MPI Intelligent Systems, Spain |
| Correspondent: | Click to Email |
Nature has evolved hydrogel-like materials that are exquisitely designed to perform specific biological functions. An example of such a material is the nuclear pore permeability barrier, a nano-sized meshwork of intrinsically disordered proteins (so called FG nups) that fills the nuclear pores (i.e. the roughly 40 nm wide channels across the nuclear envelope) and controls the entry of macromolecules into the nucleus of eukaryotic cells. The permeability barrier exhibits a unique selectivity in transport: very small molecules can cross the barrier efficiently, while larger objects are delayed or blocked unless they are bound to specialized proteins, so called nuclear transport receptors (NTRs). How size and species selectivity are encoded in the hydrogel-like properties of the permeability barrier is currently not well understood.
We have developed monolayers of end-grafted FG nups as a nano-scale model system of the permeability barrier. The planar geometry of this well-defined biomimetic film affords detailed and quantitative characterization – not accessible for the native system - with a toolbox of surface-sensitive characterization techniques. In particular, we present the application of the in situ combination of quartz crystal microbalance (QCM-D) and spectroscopic ellipsometry (SE) to quantify film thickness, hydration and viscoelastic properties as a function of protein surface density.
We will present how this experimental data, combined with polymer theory, allows us to better understand the relationship between the supramolecular organization and dynamics of the permeability barrier, its physico-chemical properties and its biological function. We demonstrate that attractive interactions between FG nups play an important role in tuning the assembly and morphology of FG nup meshworks, and highlight that even rather weak interactions – typically a few kT per biopolymer chain – have functional importance. We show also how the interaction between NTRs and FG nup meshworks is tuned to afford strong enrichment and at the same time rapid entry and exit of NTRs in the permeability barrier, thereby facilitating NTR translocation.
Taken together, these studies contribute important information to understand the mechanism of size-and species-selective transport across the nuclear pore permeability barrier. The mechanistic insight gained should be useful towards the design of bioinspired species-selective filtering devices. Moreover, the presented procedures for the acquisition and analysis of combined QCM-D/SE data are broadly applicable for the characterization of ultrathin biomolecular and other polymer films.