SPRi determination of inter-peptide interaction by using 3D supramolecular co-assembly polyrotaxane film

Accurate measurement of inter-peptide interactions is beneficial for in-depth understanding diseaserelated protein folding and peptide aggregation, and further for designing and selecting potential peptide drugs to the target antigen. Herein, we demonstrate a 3D polyrotaxane (PRX) surface for detecting peptides interactions by surface plasmon resonance imaging (SPRi). This surface is supramolecular self-assembly monolayer (SAM) structure fabricated by threading alpha-cyclodextrans (alpha-CD) through a linear polyethylene glycol (PEG) chain fixed on gold chip surface to form pseudopolyrotaxane, and further capping the pseudopolyrotaxane with bulky terminated group to form PRX film. The hydroxyl groups of alpha-CD can provide more active sites to increase molecules immobilization density, and PEG chain has unique protein non-fouling feature. We chose Alzheimer's disease marker beta-amyloid 40 (A beta 40) as model peptide, and detected the interaction between it and its inhibitors KLVFFK6 by SPRi. As a striking result, the specific adsorption of KLVFFK6 solution at the concentration of 352 mu M on A beta 40-PRX was 700 RU, whereas PEG SAM surface gave no significant binding. Interaction between other lower molecular weight peptides was detected via PRX surface, and the relatively weak interactions (K-D=1.73 x 10(-4) M) between LPFFD (Mw=0.6 kDa) and amylin20-29 (Mw = 1.0 kDa) are successfully detected. (C) 2014 Elsevier B.V. All rights reserved.