title: Quantitative study of protein-protein interactions by quartz nanopipettes.
abstract: In this report, protein-modified quartz nanopipettes were used to quantitatively study protein-protein interactions in attoliter sensing volumes. As shown by numerical simulations, the ionic current through the conical-shaped nanopipette is very sensitive to the surface charge variation near the pore mouth. With the appropriate modification of negatively charged human neuroglobin (hNgb) onto the inner surface of a nanopipette, we were able to detect concentration-dependent current change when the hNgb-modified nanopipette tip was exposed to positively charged cytochrome c (Cyt c) with a series of concentrations in the bath solution. Such current change is due to the adsorption of Cyt c to the inner surface of the nanopipette through specific interactions with hNgb. In contrast, a smaller current change with weak concentration dependence was observed when Cyt c was replaced with lysozyme, which does not specifically bind to hNgb. The equilibrium dissociation constant (KD) for the Cyt c-hNgb complex formation was derived and the value matched very well with the result from surface plasmon resonance measurement. This is the first quantitative study of protein-protein interactions by a conical-shaped nanopore based on charge sensing. Our results demonstrate that nanopipettes can potentially be used as a label-free analytical tool to quantitatively characterize protein-protein interactions.
authors: Department of Physics, Florida International University, Miami, FL 33199, USA. dariciy@fiu.edu jinhe@fiu.edu.
authors: Purushottam Babu
authors: PB
authors: Tiwari
authors: Luisana
authors: L
authors: Astudillo
authors: Jaroslava
authors: J
authors: Miksovska
authors: Xuewen
authors: X
authors: Wang
authors: Wenzhi
authors: W
authors: Li
authors: Yesim
authors: Y
authors: Darici
authors: Jin
authors: J
authors: He
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D060166:Capillary Tubing; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D058608:Nanopores / Q000648:ultrastructure*; D025941:Protein Interaction Mapping / Q000379:methods*; D011506:Proteins / Q000737:chemistry*; D011791:Quartz / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D011506:Proteins; D011791:Quartz