Dataset Information

Sensitive Analysis of Protein Adsorption to Colloidal Gold by Differential Centrifugal Sedimentation.

ABSTRACT: It is demonstrated that the adsorption of bovine serum albumin (BSA) to aqueous gold colloids can be quantified with molecular resolution by differential centrifugal sedimentation (DCS). This method separates colloidal particles of comparable density by mass. When proteins adsorb to the nanoparticles, both their mass and their effective density change, which strongly affects the sedimentation time. A straightforward analysis allows quantification of the adsorbed layer. Most importantly, unlike many other methods, DCS can be used to detect chemisorbed proteins ("hard corona") as well as physisorbed proteins ("soft corona"). The results for BSA on gold colloid nanoparticles can be modeled in terms of Langmuir-type adsorption isotherms (Hill model). The effects of surface modification with small thiol-PEG ligands on protein adsorption are also demonstrated.

SUBMITTER: Davidson AM

PROVIDER: S-EPMC5480231 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Sensitive Analysis of Protein Adsorption to Colloidal Gold by Differential Centrifugal Sedimentation.

Davidson Adam M AM Brust Mathias M Cooper David L DL Volk Martin M

Analytical chemistry 20170525 12

It is demonstrated that the adsorption of bovine serum albumin (BSA) to aqueous gold colloids can be quantified with molecular resolution by differential centrifugal sedimentation (DCS). This method separates colloidal particles of comparable density by mass. When proteins adsorb to the nanoparticles, both their mass and their effective density change, which strongly affects the sedimentation time. A straightforward analysis allows quantification of the adsorbed layer. Most importantly, unlike m ...[more]

PMID: 28513153

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Project description:The adsorption of amyloidogenic peptides, amyloid beta 1-40 (A?1-40), alpha-synuclein (?-syn), and beta 2 microglobulin (?2m), was attempted over the surface of nano-gold colloidal particles, ranging from d = 10 to 100 nm in diameter (d). The spectroscopic inspection between pH 2 and pH 12 successfully extracted the critical pH point (pHo) at which the color change of the amyloidogenic peptide-coated nano-gold colloids occurred due to aggregation of the nano-gold colloids. The change in surface property caused by the degree of peptide coverage was hypothesized to reflect the ?pHo, which is the difference in pHo between bare gold colloids and peptide coated gold colloids. The coverage ratio (?) for all amyloidogenic peptides over gold colloid of different sizes was extracted by assuming ? = 0 at ?pHo = 0. Remarkably, ? was found to have a nano-gold colloidal size dependence, however, this nano-size dependence was not simply correlated with d. The geometric analysis and simulation of reproducing ? was conducted by assuming a prolate shape of all amyloidogenic peptides. The simulation concluded that a spiking-out orientation of a prolate was required in order to reproduce the extracted ?. The involvement of a secondary layer was suggested; this secondary layer was considered to be due to the networking of the peptides. An extracted average distance of networking between adjacent gold colloids supports the binding of peptides as if they are "entangled" and enclosed in an interfacial distance that was found to be approximately 2 nm. The complex nano-size dependence of ? was explained by available spacing between adjacent prolates. When the secondary layer was formed, A?1-40 and ?-syn possessed a higher affinity to a partially negative nano-gold colloidal surface. However, ?2m peptides tend to interact with each other. This difference was explained by the difference in partial charge distribution over a monomer. Both A?1-40 and ?-syn are considered to have a partial charge (especially ?+) distribution centering around the prolate axis. The ?2m, however, possesses a distorted charge distribution. For a lower ? (i.e., ? <0.5), a prolate was assumed to conduct a gyration motion, maintaining the spiking-out orientation to fill in the unoccupied space with a tilting angle ranging between 5° and 58° depending on the nano-scale and peptide coated to the gold colloid.

Dataset Information

Sensitive Analysis of Protein Adsorption to Colloidal Gold by Differential Centrifugal Sedimentation.

Publications

Sensitive Analysis of Protein Adsorption to Colloidal Gold by Differential Centrifugal Sedimentation.

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