title: A zeptoliter volume meter for analysis of single protein molecules.
abstract: A central goal in bioanalytics is to determine the concentration of and interactions between biomolecules. Nanotechnology allows performing such analyses in a highly parallel, low-cost, and miniaturized fashion. Here we report on label-free volume, concentration, and mobility analysis of single protein molecules and nanoparticles during their diffusion through a subattoliter detection volume, confined by a 100 nm aperture in a thin gold film. A high concentration of small fluorescent molecules renders the aqueous solution in the aperture brightly fluorescent. Nonfluorescent analytes diffusing into the aperture displace the fluorescent molecules in the solution, leading to a decrease of the detected fluorescence signal, while analytes diffusing out of the aperture return the fluorescence level. The resulting fluorescence fluctuations provide direct information on the volume, concentration, and mobility of the nonfluorescent analytes through fluctuation analysis in both time and amplitude.
authors.affiliation: Laboratory of Physical Chemistry of Polymers and Membranes, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Tor
authors.initials: T
authors.lastname: Sandén
authors.forename: Romain
authors.initials: R
authors.lastname: Wyss
authors.forename: Christian
authors.initials: C
authors.lastname: Santschi
authors.forename: Ghérici
authors.initials: G
authors.lastname: Hassaïne
authors.forename: Cédric
authors.initials: C
authors.lastname: Deluz
authors.forename: Olivier J F
authors.initials: OJ
authors.lastname: Martin
authors.forename: Stefan
authors.initials: S
authors.lastname: Wennmalm
authors.forename: Horst
authors.initials: H
authors.lastname: Vogel
mesh_terms: D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D016062:Porosity; D011487:Protein Conformation; D011506:Proteins / Q000302:isolation & purification* / Q000648:ultrastructure*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014462:Ultrafiltration / Q000379:methods*
chemical_list: D011506:Proteins