Protein structural changes induced by glutathione-coated CdS quantum dots as revealed by Trp phosphorescence

We evaluated the potential of tryptophan (Trp) phosphorescence spectroscopy for investigating conformational states of proteins involved in interaction with nanoparticles. Characterization of protein–nanoparticle interaction is crucial in assessing biological hazards related to use of nanoparticles....

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Bibliographic Details
Published in:European biophysics journal 2011-11, Vol.40 (11), p.1237-1245
Main Authors: Gabellieri, E., Cioni, P., Balestreri, E., Morelli, E.
Format: Article
Language:English
Subjects:
Animals
Biochemistry
Biological and Medical Physics
Biomedical and Life Sciences
Biophysics
Cadmium Compounds - chemistry
Cell Biology
Geobacillus stearothermophilus - enzymology
Glutathione - chemistry
Glutathione - pharmacology
Life Sciences
Luminescent Measurements
Membrane Biology
Models, Molecular
Nanotechnology
Neurobiology
Original Paper
Phosphorus content
Protein Conformation - drug effects
Proteins
Proteins - chemistry
Quantum Dots
Rabbits
Sulfides - chemistry
Tryptophan - chemistry
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Summary:We evaluated the potential of tryptophan (Trp) phosphorescence spectroscopy for investigating conformational states of proteins involved in interaction with nanoparticles. Characterization of protein–nanoparticle interaction is crucial in assessing biological hazards related to use of nanoparticles. We synthesized glutathione-coated CdS quantum dots (GSH-CdS), which exhibited an absorption peak at 366 nm, indicative of 2.4 nm core size. Chemical analysis of purified GSH-CdS suggested an average molecular formula of GSH 18 S 56 Cd 60 . Investigations were conducted on model proteins varying in terms of isoelectric point, degree of burial of the Trp probe, and quaternary structure. GSH-CdS fluorescence measurements showed improvement in nanoparticle quantum yield induced by protein interaction. Trp phosphorescence was used to examine the possible perturbations in the protein native fold induced by GSH-CdS. Phosphorescence lifetime measurements highlighted significant conformational changes in some proteins. Despite their small size, GSH-CdS appeared to interact with more than one protein molecule. Rough determination of the affinity of GSH-CdS for proteins was derived from the change in phosphorescence lifetime at increasing nanoparticle concentrations. The estimated affinities were comparable to those observed for specific protein–ligand interactions and suggest that protein–nanoparticle interaction may have a biological impact.
ISSN:0175-7571
1432-1017
DOI:10.1007/s00249-011-0736-x