Polyelectrolyte-mediated protein adsorption: fluorescent protein binding to individual polyelectrolyte nanospheres.
We have used confocal fluorescence microscopy with single molecule sensitivity to characterize uptake and release of fluorescent protein (mEosFP) molecules by individual spherical polyelectrolyte brush (SPB) nanoparticles that were immobilized on a glass surface. The SPB particles consisted of a solid core particle of 100 nm diameter onto which long polyelectrolyte chains were affixed. They could be loaded with up to 30 000 mEosFP molecules in a solvent of low ionic strength. The concentration dependence of protein loading can be described with a simple bimolecular binding model, characterized by an equilibrium dissociation coefficient of 0.5 microM. Essentially complete release of the bound proteins was observed after increasing the ionic strength by adding 250 mM NaCl to the solvent. Fluorescence emission spectra and time-resolved fluorescence intensity decays were measured on individual, mEosFP-loaded SPB nanoparticles, and also on the dissolved mEosFP before and after adsorption. These results indicate that the mEosFP molecules remained structurally intact in this procedure. Hence, the present investigation demonstrates unambiguously that polyelectrolyte-mediated protein adsorption onto SPB particles presents a viable process for protein immobilization.
Anikin
Kirill
K
Department of Biophysics, University of Ulm, 89069 Ulm, Germany.
Röcker
Carlheinz
C
Wittemann
Alexander
A
Wiedenmann
Jörg
J
Ballauff
Matthias
M
Nienhaus
G Ulrich
GU
D000327:Adsorption; D004573:Electrolytes / Q000737:chemistry*; D008164:Luminescent Proteins / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D043942:Nanotubes; D011108:Polymers / Q000737:chemistry*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence
D004573:Electrolytes; D008164:Luminescent Proteins; D011108:Polymers