title: Unidirectional Living Growth of Self-Assembled Protein Nanofibrils Revealed by Super-resolution Microscopy.
abstract: Protein-based nanofibrils are emerging as a promising class of materials that provide unique properties for applications such as biomedical and food engineering. Here, we use atomic force microscopy and stochastic optical reconstruction microscopy imaging to elucidate the growth dynamics, exchange kinetics, and polymerization mechanism for fibrils composed of a de novo designed recombinant triblock protein polymer. This macromolecule features a silk-inspired self-assembling central block composed of GAGAGAGH repeats, which are known to fold into a β roll with turns at each histidine and, once folded, to stack, forming a long, ribbon-like structure. We find several properties that allow the growth of patterned protein nanofibrils: the self-assembly takes place on only one side of the growing fibrils by the essentially irreversible addition of protein polymer subunits, and these fibril ends remain reactive indefinitely in the absence of monomer ("living ends"). Exploiting these characteristics, we can grow stable diblock protein nanofibrils by the sequential addition of differently labeled proteins. We establish control over the block length ratio by simply varying monomer feed conditions. Our results demonstrate the use of engineered protein polymers in creating precisely patterned protein nanofibrils and open perspectives for the hierarchical self-assembly of functional biomaterials.
authors.affiliation: Laboratory of Physical Chemistry and Soft Matter, Wageningen University , Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
authors.forename: Lennart H
authors.initials: LH
authors.lastname: Beun
authors.affiliation: Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.|Institute for Bioengineering of Catalonia Baldiri Reixac 10-12, 08028 Barcelona, Spain.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Albertazzi
authors.affiliation: Institute for Complex Molecular Systems, Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Daan
authors.initials: D
authors.lastname: van der Zwaag
authors.affiliation: Laboratory of Physical Chemistry and Soft Matter, Wageningen University , Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
authors.forename: Renko
authors.initials: R
authors.lastname: de Vries
authors.affiliation: Laboratory of Physical Chemistry and Soft Matter, Wageningen University , Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
authors.forename: Martien A
authors.initials: MA
authors.lastname: Cohen Stuart
keywords: STORM microscopy; nanofibrils; protein polymers; self-assembly