New experimental results are reported on the self-assembling behavior of EAK16-II, the first discovered ionic self-complementary peptide, incubated at ultralow concentration (10−6 M) at neutral pH onto differently charged surfaces. It is found that strongly negatively charged surfaces promote the self-assembly of flat, micrometer-long mono-molecular fibers of side-on assembled sequences, lying onto a continuous monolayer of flat-on EAK16-II molecules. These results suggest that the monomolecular EAK16-II self-assembly is driven by the peculiar matching condition between peptide and surface electrostatic properties. Molecular Mechanics simulations of the basic bimolecular interactions confirmed the experimental inferences, showing that the flat-on state is the most stable arrangement for two interacting EAK16-II sequences onto strongly negatively charged surfaces, where indeed EAK16-II β-sheet conformation is stabilized, while the weak electrostatic interactions with mildly charged substrates promote an “entangled” EAK16-II geometry. Molecular Dynamics simulations further showed that the mobility and diffusional freedom of the peptides from the surfaces are ruled by the relative strength of peptide-surface electrostatic interactions, so that desorption probability for the peptide sequences is negligible from strongly-charged surfaces and high from mildly-charged surfaces. Furthermore, it has been found that an oligopeptide sequence lying onto two flat-on EAK16-II molecules, gains a remarkable lateral mobility, while remaining weakly bound to the surface, thus allowing the further molecular self-alignment responsible for the micrometer-long fiber formation. The reported results pave the way to the understanding and control of the subtle peptide-surface structural motifs matching enabling the formation of micrometer-long, but nanometer-wide monomolecular fibers.

Surface-driven first-step events of nanoscale self-assembly for molecular peptide fibers: An experimental and theoretical study

Forte, G.;Messina, G. M. L.;Grassi, A.;Marletta, G.
2018

Abstract

New experimental results are reported on the self-assembling behavior of EAK16-II, the first discovered ionic self-complementary peptide, incubated at ultralow concentration (10−6 M) at neutral pH onto differently charged surfaces. It is found that strongly negatively charged surfaces promote the self-assembly of flat, micrometer-long mono-molecular fibers of side-on assembled sequences, lying onto a continuous monolayer of flat-on EAK16-II molecules. These results suggest that the monomolecular EAK16-II self-assembly is driven by the peculiar matching condition between peptide and surface electrostatic properties. Molecular Mechanics simulations of the basic bimolecular interactions confirmed the experimental inferences, showing that the flat-on state is the most stable arrangement for two interacting EAK16-II sequences onto strongly negatively charged surfaces, where indeed EAK16-II β-sheet conformation is stabilized, while the weak electrostatic interactions with mildly charged substrates promote an “entangled” EAK16-II geometry. Molecular Dynamics simulations further showed that the mobility and diffusional freedom of the peptides from the surfaces are ruled by the relative strength of peptide-surface electrostatic interactions, so that desorption probability for the peptide sequences is negligible from strongly-charged surfaces and high from mildly-charged surfaces. Furthermore, it has been found that an oligopeptide sequence lying onto two flat-on EAK16-II molecules, gains a remarkable lateral mobility, while remaining weakly bound to the surface, thus allowing the further molecular self-alignment responsible for the micrometer-long fiber formation. The reported results pave the way to the understanding and control of the subtle peptide-surface structural motifs matching enabling the formation of micrometer-long, but nanometer-wide monomolecular fibers.
EAK16; Electrically charged surfaces; Electrostatic interaction; Ionic complementary peptides; Molecular dynamics; Molecular mechanics; Nanofibers; Algorithms; Amino Acid Sequence; Hydrogen-Ion Concentration; Microscopy, Atomic Force; Models, Theoretical; Nanostructures; Oligopeptides; Static Electricity; Surface Properties; Molecular Dynamics Simulation; Protein Structure, Secondary; Biotechnology; Surfaces and Interfaces; Physical and Theoretical Chemistry; Colloid and Surface Chemistry
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/357640
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