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    A pH-responsive interface derived from resilin-mimetic protein Rec1-resilin

    Year: 2010

    Journal: Biomaterials, Volume 31, Issue 15, May 2010, Pages 4434-4446, 20100827

    Authors: Truong M.Y. 1, Dutta N.K. 1, Choudhury N.R. 1, Kim M. 2, Elvin C.M 2, Hill A.J. 3, Thierry B 1, Vasilev K. 4

    Last authors: Krasimir Vasilev

    Organizations: 1 Ian Wark Research Institute, ARC Special Research Centre, Mawson Lakes Campus, University of South Australia, Mawson Lakes, SA 5095, Australia 2 CSIRO Livestock Industries, Level 6, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia 4067, Queensland, Australia 3 CSIRO Materials Science and Engineering, Clayton, Victoria, Australia 4 Mawson Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia

    Country: Australia

    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 × 1013 per cm2 at the isoelectric point (IEP 4.9), 8.79 × 1011 per cm2 at pH 2 and 9.90 × 1011 per cm2 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.