title: Molecular level investigations of the inter- and intramolecular interactions of pH-responsive artificial triblock proteins.
abstract: Intelligent materials that can undergo physical gelation in response to environmental stimuli have potential impacts in the bioengineering and biomedical fields where the entrapment of cellular or molecular species is desired. Here, we utilize atomic force microscopy (AFM) to perform molecular level investigations of designer artificial proteins that undergo physical gelation. These are engineered as triblock copolymers with independent interchain binding and solvent retention functions, namely, two terminal leucine zipper-like peptide sequences and a central alanylglycine rich sequence, respectively. AFM force measurements between probes and surfaces functionalized with molecules of this triblock protein revealed adhesive interactions that increased in average force and frequency as the pH was lowered from pH 11.2 to 7.4 to 4.5, reflecting an increase in the numbers of interacting molecular strands. In bulk solution, lowering the pH results in a viscous liquid to gel transition. The modular design of the triblock protein was also exploited for single molecule force spectroscopy investigations, which revealed altered intramolecular interactions in response to changes in pH. An increased understanding of the inter- and intramolecular forces involved in biomolecule driven gelation processes is not only of great fundamental interest in the study of the biomolecular systems involved but may also prove key in enabling the rational design of new generations of intelligent hydrogel systems.
authors.affiliation: Laboratory of Biophysics and Surface Analysis, School of Pharmacy, The University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom.
authors.forename: Molly M
authors.initials: MM
authors.lastname: Stevens
authors.forename: Stephanie
authors.initials: S
authors.lastname: Allen
authors.forename: Martyn C
authors.initials: MC
authors.lastname: Davies
authors.forename: Clive J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: Jill K
authors.initials: JK
authors.lastname: Sakata
authors.forename: Saul J B
authors.initials: SJ
authors.lastname: Tendler
authors.forename: David A
authors.initials: DA
authors.lastname: Tirrell
authors.forename: Philip M
authors.initials: PM
authors.lastname: Williams
mesh_terms: D000595:Amino Acid Sequence; D005813:Genes, Synthetic; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force / Q000379:methods; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics; D013499:Surface Properties
chemical_list: D011994:Recombinant Proteins