title: Ultrasensitive protein concentration measurement based on particle adsorption and fluorescence quenching.
abstract: A new easy-to-use method for quantification of proteins in solution has been developed. It is based on adsorption competition of the sample protein and fluorescently labeled bovine serum albumin (BSA) onto gold particles. The protein concentration is determined by observing the magnitude of fluorescence altered by quenching the fluorescence on the gold particles in a homogeneous assay format. Under optimal low pH conditions, the assay allowed the determination of picogram quantities (7.0 microg/L) of proteins with an average variation of 4.5% in a 10 min assay. The assay sensitivity was more than 10-fold improved from those of the commonly used most sensitive commercial methods. In addition, the particle sensor provides a simple and rapid assay format without requirements for hazardous test compounds and elevated temperature. Eleven different proteins were tested with the constructed sensor exhibiting a protein-to-protein variability less than 15% allowing protein concentration measurements without the need for recalibration of different proteins.
authors.affiliation: Laboratory of Biophysics and Medicity, University of Turku, Tykistokatu 6A, 20520 Turku, Finland. sari.pihlasalo@utu.fi
authors.forename: Sari
authors.initials: S
authors.lastname: Pihlasalo
authors.forename: Jonna
authors.initials: J
authors.lastname: Kirjavainen
authors.forename: Pekka
authors.initials: P
authors.lastname: Hänninen
authors.forename: Harri
authors.initials: H
authors.lastname: Härmä
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D011506:Proteins / Q000032:analysis*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D005456:Fluorescent Dyes; D011506:Proteins; D012710:Serum Albumin, Bovine; D006046:Gold