title: A pH-responsive interface derived from resilin-mimetic protein Rec1-resilin.
abstract: In this investigation, for the first time we report the effects of pH on the molecular orientation, packing density, structural properties, adsorption characteristics and viscoelastic behaviour of resilin-mimetic protein rec1-resilin at the solid-liquid interface using quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) spectroscopy. QCM-D and SPR data confirm that the binding ability of rec1-resilin on a substrate is strongly pH-dependent the protein packing density on a gold surface is calculated to be 4.45 x 10(13) per cm(2) at the isoelectric point (IEP approximately 4.9), 8.79 x 10(11) per cm(2) at pH 2 and 9.90 x 10(11) per cm(2) at pH 12, respectively. Our findings based on the thickness, dissipation and viscoelasticity of the rec1-resilin adlayer also indicate that it is adsorbed onto the gold substrate with different orientation depending on pH, such as back-on adsorption at acidic pH of 2, compact end-on bilayer adsorption at the IEP and side-on at high alkaline pH of 12. When rec1-resilin is 'pinned' to the substrate at IEP and subsequently exposed to an electrolyte solution adjusted to different pH, it switches from a compact globular conformation of the bio-macromolecule at the IEP to a coil conformation at pH between IEP to IED (IED = pKa value of tyrosine amino acid residue) and an extended coil conformation at pH > IED. This transformation from globule to coil to extended coil conformation is kinetically fast, robust and completely reversible. Such responsive surfaces created using 'smart' biomimetic rec1-resilin have the potential to find applications in many areas including biotechnology, medicine, sensors, controlled drug delivery systems and engineering.
authors.affiliation: Ian Wark Research Institute, ARC Special Research Centre, Mawson Lakes Campus, University of South Australia, Mawson Lakes, SA 5095, Australia.
authors.forename: My Y
authors.initials: MY
authors.lastname: Truong
authors.forename: Naba K
authors.initials: NK
authors.lastname: Dutta
authors.forename: Namita R
authors.initials: NR
authors.lastname: Choudhury
authors.forename: Misook
authors.initials: M
authors.lastname: Kim
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Elvin
authors.forename: Anita J
authors.initials: AJ
authors.lastname: Hill
authors.forename: Benjamin
authors.initials: B
authors.lastname: Thierry
authors.forename: Krasimir
authors.initials: K
authors.lastname: Vasilev
mesh_terms: D000327:Adsorption; D000595:Amino Acid Sequence; D000818:Animals; D032701:Biomimetics; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D020349:Surface Plasmon Resonance / Q000295:instrumentation / Q000379:methods; D014783:Viscosity
chemical_list: D029721:Drosophila Proteins; D019476:Insect Proteins; C030951:resilin